A multi-mechanism synergistically enhanced gallium oxide-based photocatalytic foam ceramic and a preparation method and application thereof

Abstract

The application discloses a multi-mechanism synergistically enhanced gallium oxide-based photocatalytic foam ceramic and a preparation method and application thereof. The method disperses gallium oxide powder, a sintering aid, a defect control agent and a photocatalytic active component in an aqueous solution containing an additive, adds a fiber reinforced phase to form a composite slurry, and then performs desludging, drying and gradient heat treatment after impregnating an organic foam, thereby in-situ constructing a photocatalytic functional phase and a heterojunction system. The obtained material mainly contains Ga2O3, can efficiently degrade PFAS, antibiotics and other refractory emerging pollutants in water, has high structural strength, high photocatalytic activity and environmental stability, solves the engineering bottlenecks of insufficient strength, active component shedding and low efficiency of traditional materials, and is suitable for the field of water treatment.

Description

Technical Field

[0001] This application relates to a gallium oxide-based photocatalytic foam ceramic with multi-mechanism synergistic enhancement, its preparation method and application, belonging to the field of inorganic non-metallic functional materials technology. Background Technology

[0002] Photocatalysis technology has become a key technology for treating emerging pollutants in water bodies due to its significant advantages such as mild reaction conditions, no secondary pollution, and controllable treatment costs. Within this technological development, monolithic photocatalytic foam ceramics, through their "structure-function integration" design, effectively solve the contradiction between the difficulty in recovering traditional powder catalysts and the insufficient active sites of immobilized catalysts, making them a current research hotspot in the field of photocatalytic water treatment.

[0003] Existing monolithic photocatalytic foam ceramic technologies mainly focus on titanium-based, zinc-based, and bismuth vanadate material systems. For example, a method for preparing monolithic BiVO4 photocatalytic foam ceramics has been disclosed in the prior art (see patent CN121623778A). This technology utilizes an organic foam impregnation method to prepare bismuth vanadate (BiVO4) with a narrow bandgap (approximately 2.4 eV) into a three-dimensional interconnected porous structure. BiVO4 materials can efficiently respond to visible light (wavelength > 420 nm), exhibiting good activity in degrading conventional organic dyes (such as azo dyes) and some emerging pollutants (such as bisphenol A), and the preparation process is relatively simple.

[0004] However, with the evolution of water pollution characteristics, existing BiVO4-based photocatalytic foam ceramics face severe challenges in dealing with stubborn organic pollutants such as perfluorinated and polyfluoroalkyl substances (PFAS) and antibiotics listed in the "List of Key New Pollutants under Control": (1) Insufficient thermodynamic oxidation driving force: BiVO4 has a shallow valence band position (about +2.4 ~ +2.7 eV vs. NHE), and its oxidation ability of photogenerated holes is limited. For perfluorinated compounds with extremely high CF bond energies (approximately 485 kJ / mol) such as PFOA and PFOS, BiVO4 struggles to provide sufficient thermodynamic driving force to break the CF bonds, resulting in extremely low mineralization efficiency and an inability to achieve complete degradation; (2) Chemical stability and photocorrosion issues: During strong oxidative degradation, BiVO4 is prone to photocorrosion and exhibits poor chemical stability under extreme pH conditions, making it difficult to meet the long-term treatment requirements of complex water quality; (3) The challenge of balancing mechanical strength and structural integrity: Existing photocatalytic foam ceramics often employ "supported" or "low-temperature sintering" strategies, resulting in weak bonding between the active components and the ceramic framework, or sacrificing mechanical strength to maintain high porosity. This makes the material prone to breakage or detachment of active components in dynamic flow environments, limiting its long-term stable operation in continuous flow reactors.

[0005] Gallium oxide (Ga2O3), as an ultrawide bandgap (~4.9 eV) semiconductor, has an extremely high photogenerated hole oxidation potential (approximately +3.5 ~ +4.0 V vs. NHE), and is theoretically an ideal material for degrading high CF bond energy perfluorinated compounds. However, the preparation of Ga2O3 into monolithic foam ceramics and its engineering application faces significant technical bottlenecks: (1) Difficulty in sintering densification: Ga2O3 has a high melting point and high volatility, and at high temperatures, it is very easy to generate Ga2O vapor, which leads to abnormal grain growth and component loss, making it difficult to obtain a dense and high-strength ceramic skeleton through conventional sintering; (2) Intrinsic brittleness and strength defects: Pure gallium oxide ceramics have extremely low intrinsic fracture toughness and are very prone to brittle fracture under the dynamic impact of actual water treatment; (3) The contradiction between activity and mass transfer: How to ensure strength during high-temperature sintering while suppressing excessive grain growth to maintain high specific surface area and photocatalytic activity is a long-standing problem in this field.

[0006] Therefore, there is an urgent need to develop a gallium oxide-based photocatalytic foam ceramic with multi-mechanism synergistic enhancement. This material needs to address the contradiction between high-temperature volatilization of Ga2O3 and sintering densification by introducing specific sintering aids and defect control agents; simultaneously, it needs to construct a high-strength, three-dimensional, interconnected porous framework through fiber / whisker reinforcement and toughening mechanisms. This invention aims to provide a photocatalytic foam ceramic that combines ultra-high mechanical strength, excellent chemical stability, and strong oxidation capability, thereby overcoming the technical bottlenecks of existing technologies where materials such as BiVO4 are unable to degrade persistent perfluorinated pollutants and where ceramic materials suffer from insufficient strength. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by providing a multi-mechanism synergistic enhancement method for gallium oxide-based photocatalytic foam ceramics, its preparation method, and its applications. This invention constructs a three-dimensional interlocking network by in-situ introducing a high aspect ratio reinforcing phase. It utilizes the strong deep-ultraviolet photocatalytic oxidation capability of Ga2O3 and the composite heterojunction system formed with photocatalytically active components to achieve efficient targeted degradation of pollutants. Simultaneously, through a systematically designed multi-element sintering aid system adapted to the sintering characteristics of Ga2O3 ceramics and a precise defect control agent scheme, high photocatalytic activity is maintained while ensuring mechanical strength.

[0008] To achieve the above objectives, the technical solution adopted in this application is as follows:

[0009] This application provides a method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement, comprising the following steps: Step S1: Preparation of gallium oxide-based composite paste Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a gallium oxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a gallium oxide-based composite slurry; Step S2: Preparation of gallium oxide-based foam ceramic wet blank The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and the excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank. Step S3: Prepare gallium oxide-based foam ceramic preform The gallium oxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic green body with a three-dimensional interconnected pore structure. Step S4: Sintering and Heterogeneous Structure Construction The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, defect control agents suppress Ga³⁺ during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization loss, excessive oxygen vacancy generation, lattice distortion, and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. At the same time, the defect structure and photoelectronic properties of the material are precisely regulated. The photocatalytic active component constructs a photocatalytic functional heterojunction system with the gallium oxide matrix through in-situ solid-phase reaction, which enhances the separation efficiency of photogenerated carriers and achieves efficient targeted degradation of target pollutants.

[0010] In step S1, the average particle size of the Ga2O3 powder is 10 nm-80 μm, preferably 100 nm-20 μm, and can be selected from any one or a combination of α-Ga2O3 phase powder, β-Ga2O3 phase powder, γ-Ga2O3 phase powder, mixed crystalline phase Ga2O3 powder or modified powder thereof. The modified powder is obtained by modifying the Ga2O3 powder through any of the following modification methods: 1) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³ + Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4+ 、Pr³ + Pr 4+ 、Nd³ + Sm³ + Eu³ + Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ +Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4+ Ir 4+ Pt² + W 6+ Pt 4+ and Au³ + Any one or more of the following, with a doping concentration of 0.1-15 at% 2) Anion doping, wherein the anion is selected from any one or more of B, C, N, F, P, S, Cl, Br and I, and the doping concentration is 0.5-10 at% 3) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10. 18 -10 21 cm -3 ; 4) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The modified powder still possesses semiconductor properties, with a band gap ranging from 1.5 to 5.5 eV; The photocatalytic active component is an inorganic oxide powder with semiconductor properties, and its band gap ranges from 1.5 to 5.5 eV; it is selected from at least one component from the following I) - V); I) Single metal oxides The general chemical formula is M m O n M is a single metallic element, m = 1-3, n = 1-5; including one or more of TiO2, ZnO, WO3, Bi2O3, Fe2O3, Cu2O, V2O5, MoO3, SnO2, MnO2, ZrO2, Nb2O5, Ta2O5, In2O3, GeO2, RuO2, IrO2, Co3O4, NiO, Mn3O4, CuO, Ag2O, CoO, MnO, SnO, Sb2O3, Fe3O4, and Au2O and their modified derivatives; II) Composite metal oxides Composed of two or more metal cations, and further subdivided according to crystal structure as: a) Perovskites and their derived phases: general formula ABO3 or A (n+1) B n O (3n+1), where n is an integer from 1 to 3, A is selected from at least one of La, Bi, Ba, Sr, Ca, Pb, Na and K, and B is selected from at least one of Ti, Zr, Hf, Nb, Ta, W, Mo, V, Cr, Mn, Fe, Co, Ni, Al, Ga and Sn; b) Spinel-type oxides: with the general formula AB2O4, wherein A is selected from at least one of Mg, Zn, Ni, Co, Cu, Fe, Mn and Li, and B is selected from at least one of Al, Ga, Cr, Fe, Mn, Co and Ti; c) Layered oxyacid salts having a layered crystal structure with an interlayer spacing of 0.5 nm to 1.5 nm, selected from at least one of the following: c1) Layered titanates, with the general formula A2Ti3O7 or ATi2O5, wherein A is selected from H, Li, Na, K, Rb or Cs; C2) Protonated layered niobates or tantalates, with the general formula HNb3O8 or HTa2O6; C3) Aurivillius phase bismuth-based oxides, selected from Bi2WO6, Bi2MoO6, and Bi4Ti3O 12 At least one of them; c4) Layered nickelates, with the general formula ANiO2, wherein A is selected from Li or Na; d) Other functional oxoacid salts, selected from at least one of the following groups: d1) Scheelite-type oxides, with the general formula AWO4, AMoO4 or AVO4, wherein A is selected from Bi, Ca, Sr, Zn or Pb; d2) Perovskite-type rare earth ferrates, with the general formula LnFeO3, wherein Ln is selected from La, Pr, Nd or Sm; d3) Pyrochlore-type oxides, with the general formula Ln2B2O7, wherein Ln is selected from La, Gd, Sm or Nd, and B is selected from Ti, Zr or Sn; d4) Tungsten bronze type oxide, with the general formula M x TO3, where T is selected from W, Nb, or Ta, M is selected from Na or K, and 0.1 ≤ x ≤ 1.0; d5) Olivine-type oxides, with the general formula M2SiO4 or M2GeO4, wherein M is selected from Mg, Zn, Fe or Mn; d6) Inverse spinel-type stannate Zn2SnO4; d7) Copper-iron ore type oxides, with the general formula CuMO2, wherein M is selected from Fe, Al, Ga or Cr; III) Rare earth-based oxides a) Single rare earth oxide Ln a O x , where Ln is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, a = 1–2, x = 1.5–3; b) Rare earth composite oxides: including perovskite-type LaMO3, NdMO3, ScMO3, YMO3, PrMO3, SmMO3, EuMO3, GdMO3, TbMO3, DyMO3, HoMO3, ErMO3, TmMO3, YbMO3, and LuMO3, where M is selected from transition metals Fe, Co, Sc, Ti, V, Cr, Mn, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, and W. Re, Os, Ir, Pt, Au, or Hg; pyrochlore-type Gd₂Ti₂O₇, Y₂Zr₂O₇, Sc₂Ti₂O₇, La₂Ti₂O₇, Ce₂Ti₂O₇, Pr₂Ti₂O₇, Nd₂Ti₂O₇, Sm₂Ti₂O₇, Eu₂Ti₂O₇, Tb₂Ti₂O₇, Dy₂Ti₂O₇, Ho₂Ti₂O₇, Er₂Ti₂O₇, Tm₂Ti₂O₇, Yb₂Ti₂O₇, Lu₂Ti₂O₇; bismuth rare earth co-doped oxides Bi. 1-x Ln x VO4, wherein Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, x = 0.1-0.5, and at least one of the layered rare earth oxides La2O2CO3, Pr4O7, Ce2O2CO3, Nd2O2CO3, Sm2O2CO3, Eu2O2CO3, Gd2O2CO3, Tb2O2CO3, Dy2O2CO3, Ho2O2CO3, Er2O2CO3, Tm2O2CO3, Yb2O2CO3, Lu2O2CO3, Sc2O2CO3, Y2O2CO3; the interlayer spacing of the layered rare earth oxide structure is 0.8-1.2 nm; IV) Frontier structural metal oxides a) High-entropy oxides: general formula is (M1, M2, ... M n ) a O M1, M2, ..., Mn are at least five different metallic elements, each independently selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Al, Li, Zr, Nb, Mo, Sn, Hf, Ta, W, or Ce, with each metallic element accounting for 5% to 35% of the total metallic elements, and the configuration entropy ΔS of the high-entropy oxide is... mix ≥ 1.5R, where R is the ideal gas constant 8.314 J·mol - ¹·K - ¹; (b) A two-dimensional nano-metal oxide, wherein the matrix material of the two-dimensional nano-metal oxide is selected from at least one of TiO2, MnO2, MoO3, V2O5, Co3O4, Fe2O3, SnO2, ZnO, WO3 and Nb2O5, has a plate-like or layered morphology, has a thickness of 0.5 nm to 10 nm, has a lateral dimension to thickness ratio ≥ 50, and the two-dimensional nano-metal oxide has preferentially exposed crystal planes, wherein the crystal planes are selected from at least one of the {001}, {010}, {100} and {110} plane families; c) MOF-derived porous oxides, wherein the MOF-derived porous oxides are obtained by heat treatment conversion of metal-organic framework precursors, wherein the metal center of the precursor is selected from at least one of Zn, Co, Fe, Cu, Zr, Ti, Ni and Al, and the resulting oxides retain the morphological characteristics and pore structure of the precursors, with a specific surface area ≥ 50 m² / g, pore volume ≥ 0.1 cm³ / g, and pore size distribution spanning from micropores to mesopores, ranging from 0.5 nm to 50 nm; V) Precursor compound: is the water-insoluble oxalate and / or carbonate corresponding to the metal oxides in I)-II), wherein the precursor compound decomposes in situ during sintering heat treatment to generate the corresponding photocatalytically active oxide; Wherein, "insoluble in water" means: solubility in deionized water at 25°C ≤ 0.1 g / 100 mL; the precursor compound must meet the following requirements: decomposition temperature between 200-1200°C, residual carbon content after decomposition < 0.1 wt.%, and no introduction of impurity anions harmful to photocatalytic activity; VI) The photocatalytic active component described in any of I) to IV) above is modified using one or more of the following methods, and the resulting powder satisfies a band gap of 1.5-5.5 eV: a) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs+ 、Mg² + 、Ca² + 、Sr² + 、Ba² + 、Al³ + 、In³ + 、Sn 4+ 、Sb³ + 、Sb 5+ 、Bi³ + 、Sc³ + 、Tea 4+ 、V³ + 、V 4+ 、V 5+ 、Cr³ + 、Cr 4+ 、Mn² + 、Mn³ + 、 Mr 4+ 、Fe² + 、Fe³ + 、Co² + 、Co³ + 、Ni² + 、Ni³ + 、Cu² + 、Zn² + 、Y³ + 、Zr 4+ 、Nb 5+ 、Mo 6+ 、Ru 4+ 、Rh³ + 、Pd² + 、Ag + 、Day³ + 、Ce³ + 、Ce 4+ 、Pr³ + 、Pr 4+ 、Nd³ + 、Sm³ + 、Eu³ + 、Gd³ + 、Tb³ + 、Tb 4+ 、Dy³ + 、Ho³ + 、Er³ + 、Tm³ + 、Yb³ + 、Lu³ + 、Hf 4+ 、Ta 5+ 、Re 4+ 、Re 6+ 、Os 4+ 、Ir 4+ 、Pt²+ Pt 4+ W 6+ and Au³ + At least one of them, with a doping ratio of 0.1-15 at%; b) Anion doping, wherein the anion is selected from one or more of B, C, N, F, P, S, Cl, Br and I, and the doping ratio is 0.5-10 at% c) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10. 18 -10 21 cm -3 ; d) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The amount of the photocatalytic active component added is 5-80 wt.% of the gallium oxide powder mass; the amount of the precursor compound added is based on the theoretical mass of the corresponding photocatalytic active oxide generated by its complete thermal decomposition, i.e., oxide equivalent. The sintering aid is selected from at least one of the following components: a. Low-melting-point oxides With a melting point <900℃, it partially melts within the sintering temperature window, providing a transient liquid phase to promote mass transfer and densification between Ga2O3 particles. It mainly comprises the following components: Bismuth trioxide (Bi2O3), vanadium pentoxide (V2O5), boron trioxide (B2O3), molybdenum trioxide (MoO3), tellurium dioxide (TeO2); b. Eutectic type / active oxide Individual components can have melting points exceeding 900℃, but they form low-melting-point eutectics with Ga2O3 or undergo solid-state reactions with Ga2O3 to generate low-melting-point active phases, promoting low-temperature densification. Simultaneously, some components can react in situ with Ga2O3 to generate new gallium-based functional phases with photocatalytic activity, achieving a dual contribution of sintering aid and enhanced photocatalytic function. These components mainly include the following: Zinc oxide (ZnO), copper oxide (CuO), ferric oxide (Fe2O3), nickel oxide (NiO), cobalt oxide (CoO), cobalt tetroxide (Co3O4), manganese dioxide (MnO2), manganese trioxide (Mn2O3), chromium trioxide (Cr2O3), indium trioxide (In2O3), antimony trioxide (Sb2O3), tin dioxide (SnO2); c. Network forming agents A low-viscosity glassy liquid phase is formed at the sintering temperature, filling the gaps between Ga2O3 particles. The Ga2O3 particles are rearranged by surface tension, achieving low-temperature liquid phase sintering. The main components are as follows: Silicon dioxide (SiO2), phosphorus pentoxide (P2O5), germanium dioxide (GeO2), tellurium dioxide (TeO2), and boron trioxide (B2O3); d. Alkali metal and alkaline earth metal oxides As a network modifier, it reduces liquid phase viscosity by breaking bridging oxygen bonds in the glass network; simultaneously, it can form alkali metal / alkaline earth metal gallates with Ga2O3, controlling the sintering path. Its main components include the following: Magnesium oxide (MgO), lithium carbonate (Li2CO3), calcium carbonate (CaCO3), strontium carbonate (SrCO3), barium carbonate (BaCO3); e. Rare earth oxide sintering aids Rare earth ion radii are much larger than those of Ga³ + It has extremely low solid solubility in the Ga2O3 lattice and mainly segregates to the grain boundaries to form rare earth gallium composite oxide grain boundary phases. It plays a role in both sintering aid and grain growth inhibition through liquid-phase assisted sintering and grain boundary pinning mechanisms. It mainly consists of the following components: Lanthanum oxide (La₂O₃), yttrium oxide (Y₂O₃), scandium oxide (Sc₂O₃), neodymium oxide (Nd₂O₃), samarium oxide (Sm₂O₃), gadolinium oxide (Gd₂O₃), dysprosium oxide (Dy₂O₃), erbium oxide (Er₂O₃), ytterbium oxide (Yb₂O₃), cerium oxide (CeO₂), praseodymium oxide (Pr₆O₃) 11 Terbium oxide (Tb4O7), europium oxide (Eu2O3), holmium oxide (Ho2O3), thulium oxide (Tm2O3), and lutetium oxide (Lu2O3); f. Pre-synthesized gallium-based functional compounds Pre-synthesized gallium salts or gallium-based composite oxides are directly introduced into the system as sintering aids, preferentially providing activated mass transfer channels between Ga2O3 particles to promote densification. Simultaneously, an in-situ Ga2O3 heterojunction interface is constructed, mainly comprising the following components: Zinc gallate (ZnGa2O4), magnesium gallate (MgGa2O4), cobalt gallate (CoGa2O4), nickel gallate (NiGa2O4), copper gallate (CuGa2O4), iron gallate (FeGaO3), indium gallate (InGaO3), aluminum gallate (AlGaO3), calcium gallate (CaGa4O7), strontium gallate (SrGa2O4), barium gallate (BaGa2O4), gallium vanadate (GaVO4), gallium molybdate (Ga2(MoO4)3), gallium tungstate (Ga2(WO4)3), bismuth gallium oxide (BiGaO3), lithium gallate (LiGaO2); g. Precursor compounds The oxalates, carbonates or hydroxides corresponding to each component in (a) to (f) above that are insoluble in water decompose in situ during degumming or sintering heat treatment to generate corresponding oxides or oxygen-containing compounds. The term "insoluble in water" means that the solubility in deionized water at 25°C is ≤0.1g / 100mL. The precursor compound is uniformly dispersed in solid particle form during the slurry stage, and decomposes in situ during heat treatment to produce nano-sized active powder. The dispersion uniformity is better than that of directly adding oxides. A typical precursor compound includes the following components: Bismuth carbonate (Bi2(CO3)3), copper oxalate (CuC2O4), ferrous oxalate (FeC2O4), zinc oxalate (ZnC2O4), tin oxalate (SnC2O4), nickel oxalate (NiC2O4), cobalt oxalate (CoC2O4), manganese oxalate (MnC2O4), calcium carbonate (CaCO3), barium carbonate (BaCO3), strontium carbonate (SrCO3), lanthanum carbonate (La2(CO3)3), lanthanum oxalate (La2(C2O4)3), cerium oxalate (Ce2(C2O4)3), lithium carbonate (Li2CO3), sodium carbonate (Na2CO3), potassium carbonate (K2CO3); The total amount of the sintering aid added is 0.2-30 wt.% of the mass of gallium oxide powder; for components (a) to (f), it is based on their actual added mass; for component (g), it is based on the theoretical mass (oxide equivalent) of the corresponding oxide generated by its complete thermal decomposition. It is particularly noted that the bifunctional sintering aids (such as ZnO, CuO, Fe2O3, In2O3, etc.) in the sintering aids can promote the low-temperature densification of Ga2O3, and at the same time, they can undergo in-situ solid-phase reactions with Ga2O3 to generate new phases with photocatalytic activity (such as ZnGa2O4, CuGaO2, Ga2O3 / Fe2O3 heterojunction, etc.), thus realizing the dual contribution of sintering aids in densification promotion and photocatalytic function enhancement. The defect control agent (also known as grain growth inhibitor, valence state compensator, or grain boundary modifier, etc.) is selected from at least one of the following components: a. Equivalent substitution stabilizers With Ga³ + Same price (M³) + By stabilizing the Ga2O3 lattice through solid solution substitution, the lattice binding energy is increased without introducing additional charge imbalance, thus suppressing Ga³ + →Ga 0 Excessive reduction and Ga2O volatilization losses include the following components: Aluminum oxide (Al2O3), ferric oxide (Fe2O3), chromium oxide (Cr2O3), indium oxide (In2O3), scandium oxide (Sc2O3), boron oxide (B2O3); b. Donor-type substitution stabilizers When a metal ion Mn+ with a valence state n>3 substitutes for Ga3+, a substitutional defect MGa•(n) with a net positive charge is generated in the crystal lattice. 3) This positive charge center compensates for the gallium vacancies VGa, which are acceptor defects, by providing additional electrons. This suppresses the formation of additional donor defects (such as interstitial gallium Gai••• or oxygen vacancies VO•••). Simultaneously, by increasing the Fermi level of the system, Ga³3 is thermodynamically suppressed. + →Ga 0 The reduction and volatilization of Ga2O effectively maintain the integrity of the Ga2O3 crystal structure. After solid solubility saturation, it segregates to the grain boundaries, forming a high-valence oxide grain boundary pinning phase, which effectively inhibits abnormal growth of Ga2O3 grains. This phase includes the following components: Tin dioxide (SnO2), germanium dioxide (GeO2), silicon dioxide (SiO2), titanium dioxide (TiO2), zirconium dioxide (ZrO2), hafnium dioxide (HfO2), niobium pentoxide (Nb2O5), tantalum pentoxide (Ta2O5), tungsten trioxide (WO3), molybdenum trioxide (MoO3), vanadium pentoxide (V2O5), antimony pentoxide (Sb2O5); c. Acceptor-substituted stabilizers When divalent metal ions M 2+ Replace Ga 3+ At this time, a substitutional defect MGa′ with a net negative charge is generated, forming an acceptor-type defect compensation mechanism. This mechanism reduces the donor-type intrinsic defects (such as oxygen vacancies V) by suppressing the Fermi level. O •• Ga interstitial Ga i ••• The concentration of β-Ga2O3 is controlled to thermodynamically regulate the defect structure equilibrium and maintain the photocatalytically active phase structure of β-Ga2O3. Some components form photocatalytically active composite phases (such as ZnGa2O4, MgGa2O4, etc.) in Ga2O3, achieving synergy between defect control and photocatalytic function enhancement. These components include the following: Magnesium oxide (MgO), zinc oxide (ZnO), nickel oxide (NiO), cobalt oxide (CoO), copper oxide (CuO), manganese oxide (MnO), ferrous oxide (FeO), beryllium oxide (BeO); d. Grain boundary segregation inhibitors The ionic radius is much larger than that of Ga³ +(0.062 nm), mainly through grain boundary segregation mechanism, it inhibits abnormal growth of Ga2O3 grains through solute drag effect, maintaining fine-grained structure and high specific surface area; at the same time, the grain boundary segregated phase can block the grain boundary diffusion channels of Ga2O vapor, inhibiting the volatilization loss of Ga2O at high temperature, including the following components: Lanthanum trioxide (La₂O₃), yttrium oxide (Y₂O₃), neodymium oxide (Nd₂O₃), praseodymium oxide (Pr₆O₃) 11 Samarium oxide (Sm2O3), europium oxide (Eu2O3), gadolinium oxide (Gd2O3), terbium oxide (Tb4O7), dysprosium oxide (Dy2O3), holmium oxide (Ho2O3), erbium oxide (Er2O3), thulium oxide (Tm2O3), ytterbium oxide (Yb2O3), cerium dioxide (CeO2), and lutetium oxide (Lu2O3); e. Oxygen activity self-regulating stabilizer Compounds with reversible redox pairs maintain a localized oxidizing atmosphere around Ga2O3 particles during Ga2O3 sintering through a dynamic oxygen release / storage mechanism, thereby thermodynamically inhibiting the oxidation of Ga³⁺. + →Ga 0 The reduction reaction produces Ga₂O vapor, which includes the following components: Cerium dioxide (CeO2), manganese dioxide (MnO2), manganese trioxide (Mn2O3), manganese trioxide (Mn3O4), praseodymium oxide (Pr6O) 11 Terbium oxide (Tb4O7), cobalt tetroxide (Co3O4), cobalt oxide (CoO), ferric oxide (Fe2O3), and ferric oxide (Fe3O4); f. Precursor compounds The water-insoluble oxalates and / or carbonates corresponding to each component in (a)-(e) above decompose in situ to generate corresponding oxides during the sintering heat treatment process. The term "insoluble in water" means that the solubility in deionized water at 25°C is ≤0.1g / 100mL. Typical precursor compounds include: aluminum oxalate (Al2(C2O4)3), ferrous oxalate (FeC2O4), chromium oxalate (Cr2(C2O4)3), scandium oxalate (Sc2(C2O4)3), indium oxalate (In2(C2O4)3), tin oxalate (SnC2O4), zirconium carbonate (ZrOCO3), titanium oxalate (TiO(C2O4)), and niobium oxalate (NbO(C2O4)). Magnesium oxalate (MgC2O4), zinc oxalate (ZnC2O4), nickel oxalate (NiC2O4), cobalt oxalate (CoC2O4), manganese oxalate (MnC2O4), cerium oxalate (Ce2(C2O4)3), lanthanum oxalate (La2(C2O4)3), neodymium oxalate (Nd2(C2O4)3), gadolinium oxalate (Gd2(C2O4)3), yttrium oxalate (Y2(C2O4)3); The total amount of the defect control agent added is 0.1-15 wt.% of the mass of gallium oxide powder: for components (a) to (e), it is based on the actual added mass; for component (f), it is based on the theoretical mass of the corresponding oxide generated by complete thermal decomposition, i.e., the oxide equivalent. It should be noted that the defect control mechanism in the Ga2O3 system differs fundamentally from that in the ZnO system. In the ZnO system, the Zn site is Zn². + M³ + Replace Zn² + Donor defects are formed; however, in the Ga₂O₃ system, the Ga site is Ga³. + Mn+ (n>3) replaces Ga³ + The donor defect is formed, M² + Replace Ga³ + This forms acceptor defects, and the two can synergistically regulate the donor-acceptor defect balance in the Ga2O3 system; the main intrinsic sintering problem of Ga2O3 lies in the high temperature of Ga³ + Excessive reduction of Ga₂O (gas phase) leads to its volatilization, resulting in uncontrolled grain growth and component loss. Therefore, donor-type high-valence oxides (component b) thermodynamically inhibit Ga³ through Fermi level elevation. + Reduction is the most effective defect control mechanism; rare earth grain boundary segregating agent (component d) simultaneously exerts defect stabilization and grain growth inhibition functions by blocking grain boundary diffusion channels; oxygen activity self-regulating stabilizer (component e) maintains the local oxidizing properties of the sintering atmosphere from a kinetic perspective, complementing the thermodynamic regulation mechanism of donor dopants; the defect control agent described in this application is specifically optimized and screened for the Ga2O3 system, taking into account the synergistic optimization of five major mechanisms: equivalent solid solution stabilization, donor high-valence compensation, acceptor defect balance, rare earth grain boundary inhibition, and oxygen activity self-regulation; The defect control agent is used to suppress Ga³ during high-temperature sintering. +Excessive reduction and loss of Ga2O volatilization, excessive generation of oxygen vacancies, lattice distortion and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintain a high specific surface area and porosity of the material, and ensure a high retention ratio of the Ga2O3 photocatalytic active phase. The organic additives include at least one of binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; The organic additives are used alone or in combination, with a total addition amount of 0.1-30 wt.% of the total mass of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents. The adhesive is selected from at least one of the following components: polyethylene oxide (PEO), sodium alginate (SA), chitosan (CTS), polyurethane emulsion (PU), polyacrylamide (PAM), polyvinyl alcohol (PVA), methylcellulose (MC), hydroxypropyl methylcellulose (HPMC), ethylcellulose (EC), polyethylene glycol (PEG, molecular weight 200-20,000), polyacrylic acid (PAA), polyvinyl acetate (PVAc), starch (ST) and its derivatives; The plasticizer is selected from at least one of the following components: triethyl acetylglucosamine citrate (ATEC), epoxidized soybean oil (ESO), polycaprolactone (PCL), glycerin (GLY), dibutyl phthalate (DBP), triethyl citrate (TEC), polyethylene glycol (PEG), sorbitol (SORB), and dioctyl sebacate (DOS). The dispersant is selected from at least one of the following components: polycarboxylate superdispersants (such as Solsperse). TM 32000, Tamol TM SN), polymaleic anhydride (PMA), polyaspartic acid (PASP), ammonium polyacrylate (NH4PAA), sodium polyacrylate (NaPAA), tetramethylammonium hydroxide (TMAH), ammonium citrate (AC), gum arabic (GA) and polyvinylpyrrolidone (PVP). The surfactant is selected from at least one of the following components: sorbitan monooleate (Span-80), cocamidopropyl betaine (CAB), perfluoropolyethers (such as Zonyl® FSO), sodium dodecyl sulfate (SDS), hexadecyltrimethylammonium bromide (CTAB), polysorbate 80 (Tween-80), octylphenyl polyoxyethylene ether (Triton X-100), lecithin (LC), and fluorocarbon surfactants (such as Capstone® FS-30); The rheology modifier is selected from at least one of the following components: guar gum (GG), gellan gum (GeG), polyacrylic acid thickeners (such as Carbopol® 940), organic modified montmorillonite (such as Bentonex®), xanthan gum (XG), sodium carboxymethyl cellulose (CMC), bentonite (BT), fumed silica (FS), and polyacrylamide (PAM). The defoamer is selected from at least one of the following components: polydimethylsiloxane (PDMS), polyether defoamer (such as Pluronic® L61), isooctanol (IOA), n-octanol (NOA), silicone oil (such as Dow Corning® 200 Fluid), polyether modified siloxane (such as BYK-024), and mineral oil (MO). The pH adjuster is at least one of ammonia (NH3·H2O, 1-10 mol / L) and hydrochloric acid (HCl, 1-10 mol / L); The reinforcing phase is fibers and / or whiskers, selected from any one or more of the following: (1) Inorganic fibers: glass fiber, basalt fiber, silicon carbide fiber, alumina fiber, mullite fiber, quartz fiber, potassium titanate fiber, aluminum nitride fiber, etc. (2) Ceramic whiskers: silicon carbide whiskers, zinc oxide whiskers, calcium sulfate whiskers, silicon nitride whiskers, barium titanate whiskers, aluminum borate whiskers, magnesium borate whiskers, sodium titanate whiskers, potassium titanate whiskers, zirconium oxide whiskers, aluminum oxide whiskers, calcium carbonate whiskers, aluminum nitride whiskers, etc. (3) Natural mineral fibers: sepiolite fiber, attapulgite fiber, wollastonite fiber, palygorskite fiber, tremolite fiber, actinolite fiber, vermiculite fiber, sillimanite fiber, tourmaline fiber, etc. (4) Synthetic organic fibers: polyacrylonitrile fiber, polyvinyl alcohol fiber, aramid fiber, polyimide fiber, etc. (completely pyrolyzed during degumming heat treatment, playing a role in pore formation and pre-toughening). (5) Metal whiskers: tin whiskers, copper whiskers, silver whiskers, nickel whiskers, iron whiskers, zinc whiskers, aluminum whiskers, gold whiskers, platinum whiskers, cobalt whiskers, titanium whiskers, niobium whiskers, zirconium whiskers, tungsten whiskers, molybdenum whiskers, rhenium whiskers, tantalum whiskers, palladium whiskers, chromium whiskers, magnesium whiskers, cadmium whiskers, etc.; (6) Metal fibers: stainless steel fiber, copper fiber, aluminum fiber, nickel fiber, titanium fiber, silver fiber, gold fiber, platinum fiber, palladium fiber, iron fiber, steel fiber, tungsten fiber, molybdenum fiber, niobium fiber, tantalum fiber, zirconium fiber, hafnium fiber, magnesium fiber, zinc fiber, tin fiber, lead fiber, cadmium fiber, cobalt fiber, chromium fiber, beryllium fiber, nickel-titanium alloy fiber, iron-chromium-aluminum alloy fiber, nickel-chromium alloy fiber, Invar alloy fiber, etc.; Wherein, the aspect ratio of the reinforcing phase is ≥ 10; The gallium oxide-based composite slurry has a solid content of 20-70 vol.% and a pH of 2-14. The amounts of organic additives and reinforcing phases added (based on the total mass of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents) are as follows: Adhesive 1-20 wt.%; Dispersant 0.1-5 wt.%; Plasticizer 0.1-10 wt.%; Surfactant 0.01-5 wt.%; Rheology modifier 0.1-10 wt.%; Defoamer 0.05-10 wt.%; pH adjuster 0.01-10 wt.%; Reinforcing phase: 0.01-30 wt.% (fibers) or 0.01-50 wt.% (whiskers); In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the gallium oxide-based suspension slurry and the composite slurry are uniformly dispersed by mechanical stirring and / or ball milling. For uniform dispersion of the homogeneous solution, the mechanical stirring rate is 100-3000 rpm; the stirring time is 0.5-180 min; the stirring paddle is made of inert material, preferably polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container is 0.1-2 cm. When mechanical stirring is used to uniformly disperse gallium oxide-based suspension slurry and gallium oxide-based composite slurry, the stirring speed range is 20-3000 rpm; the stirring time range is 15-1500 min; the stirring paddle material is inert; and the distance between the stirring paddle blade and the bottom of the slurry container ranges from 0.1-50 cm. When uniformly dispersing gallium oxide-based suspension slurry and gallium oxide-based composite slurry using ball milling, the ball milling container used for ball milling is made of an inert material, preferably polytetrafluoroethylene; the ball-to-material weight ratio is 0.2-12; the ball milling time is 30-1500 min; the diameter of a single grinding ball is 0.2-12 mm, and the average diameter is 3-8 mm.

[0011] In some embodiments, in step S2, the organic foam is made of polyurethane (PU), melamine formaldehyde (MF), or polystyrene (PS), preferably polyurethane foam (PU); the pore density of the organic foam is in the range of 6-70 PPI, and its macroscopic shape is any one of the following: cylinder, cube, cuboid, sphere, ellipsoid, torus, prism, pyramid, polyhedron, honeycomb block, sheet, arc, arch, tubular, hollow spherical shell, or any combination and deformation thereof; The impregnation is carried out using normal pressure, negative pressure assisted, or alternating negative and normal pressure methods; the impregnation process is carried out at 25±20℃, the normal pressure impregnation time is 30-1800 seconds, and the number of negative and normal pressure alternating impregnations is 1-5 times per impregnation cycle; The negative pressure assistance involves completely immersing the organic foam in the gallium oxide-based composite slurry described in step S1, then evacuating the composite slurry to boiling point within 3 minutes, maintaining boiling for 0.5-10 minutes to ensure that all air in the system is expelled, and then restoring it to ambient pressure. The pressure of the extrusion desizing is controlled at 0.1-10 MPa, and the thickness of the organic foam after extrusion is compressed to 30-95% of the original thickness; The centrifugal desizing process is performed at a speed of 500-5000 rpm for 10-900 seconds. The drying process employs a programmed temperature increase method, with a temperature range of 20~95℃ and relative humidity gradually decreasing from ≥70% to <10%, drying until the mass change rate is <20% / h. After each impregnation-desizing-drying-impregnation cycle, the mass gain rate of the composite slurry loaded in the organic foam is 20-600%. After 2-5 cycles, the cumulative loading of the composite slurry reaches 150-1000% of the original mass of the organic foam, forming a coating thickness of 0.1-3.0 mm, a slurry coating thickness variation coefficient of <30%, and a pore blockage rate of <40%.

[0012] In some embodiments, in step S3, the natural air drying is carried out in a ventilated environment with a temperature of 5-45°C, a relative humidity of 30-90%, a ventilation rate of 0.1-10.0 m / s, and a natural air drying time of 2-24 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 50-95℃ at a rate of 0.1-20℃ / min, and the temperature is maintained for 4-24 hours. The airflow rate in the oven is 0.01-10 m / s, and the drying endpoint is a mass change rate of <0.1% / h. The degumming heat treatment includes: The first stage involves raising the temperature at a rate of 1-10℃ / min to 150-250℃ and holding it for 1-360 min. In the second stage, the temperature is increased to 350-450℃ at a rate of 0.5-10℃ / min, and then held for 1-360 min. The third stage involves raising the temperature at a rate of 0.5-10℃ / min to 550-600℃ and holding it for 1-360 min. The degumming heat treatment process is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 100 Pa. The atmospheric conditions are: at least one of helium, argon, nitrogen, ammonia, air or oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50 ~ +9000 Pa.

[0013] In some embodiments, in step S4, the controlled sintering heat treatment temperature is 900-1700℃, the heating rate is 2-20℃ / min, and the holding time is 0.01-24 hours. The controlled sintering heat treatment is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 10 Pa. The atmospheric conditions are: at least one of hydrogen, helium, argon, nitrogen, ammonia, air and oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50~+9000 Pa. This application strictly sets the upper limit of the controlled sintering heat treatment temperature to 1700°C, and it must not exceed 1700°C, in order to effectively prevent Ga2O3 from deteriorating due to Ga³ in high-temperature (above 1600°C) environments. + Excessive reduction leads to significant Ga2O vapor volatilization loss and rapid Ga2O3 grain growth. The actual sintering temperature should be determined comprehensively based on the melting point and eutectic temperature of the sintering aids in the system, and is recommended to be selected within the range of 900℃ to 1600℃ to achieve the optimal balance between matrix densification and Ga2O volatilization suppression. This range comprehensively considers the melting point characteristics of the sintering aids and the eutectic reaction temperature, aiming to find the optimal balance between matrix densification and volatile component suppression. Furthermore, the various process parameters of the controlled sintering heat treatment, including heating rate, holding time, and atmosphere control, are synergistically regulated based on the sintering kinetics, thermal stability threshold, microstructural evolution of microstructures, and grain growth behavior of gallium oxide-based photocatalytic foam ceramics, while also fully considering the thermal sensitivity of the active components. Through the above precise regulation, this process can synergistically achieve the following technical objectives: First, a three-dimensional network framework reinforced with fibers / whiskers is constructed to achieve synergistic optimization of mechanical strength and mass transfer efficiency. Using ceramic fibers or whiskers as the reinforcing framework, the Ga2O3 matrix and photocatalytically active components are sintered together to form a three-dimensional porous network with excellent structural integrity. Simultaneously, through precise process control, the width of the interparticle connection region, i.e., the sintering neck, is controlled within the range of 0.1 μm to 50 μm. This specific sintering neck structure, while ensuring high connectivity and low fluid resistance of the three-dimensional channels, effectively achieves efficient stress transfer between the reinforcing phase and the matrix, thereby synergistically improving the macroscopic mechanical strength of the foam ceramic and the microscopic mass transfer efficiency of the reactants, providing a stable structural support for efficient photocatalytic degradation.

[0014] Second, implement multi-mechanism defect engineering control to suppress abnormal grain growth and component volatilization. This is achieved through solid solution substitution and grain boundary segregation mechanisms using defect control agents to control Nb... 5+ Ta 5+ Sn 4+ 、Ge 4+ Si 4+ High-valence cations replace Ga³ in the Ga₂O₃ lattice + Sites form shallow donor levels, which thermodynamically suppress Ga³ through the rise of the Fermi level. + To Ga 0 Excessive reduction and Ga2O vapor volatilization; causing Y³ + La³ + Gd³ + Rare earth ions with similar ionic radii are due to their similarity to Ga³⁺. + Significant differences in ionic radius lead to segregation into the Ga2O3 grain boundary region, forming a rare-earth-rich grain boundary segregation layer. This effectively suppresses abnormal Ga2O3 grain growth through the solute dragging effect, thus reducing Mg²⁺ precipitate. + Zn² + Divalent acceptor-type doped Ga³ + The lattice sites form an acceptor defect compensation mechanism, reducing the concentration of donor-type intrinsic defects such as oxygen vacancies and gallium interstitials. Ultimately, the average particle size D50 of Ga2O3 is controlled within the range of 0.01 μm to 10 μm, ensuring that the foam ceramic framework possesses a preset specific surface area threshold and interconnected porosity to maintain effective exposure of the photocatalytic reaction interface and the mass transfer efficiency of the reactants.

[0015] Third, constructing a strong chemically bonded interface establishes the structural safety of the foam ceramic. This significantly enhances the interfacial chemical bonding strength between the ceramic fiber or whisker reinforcing phase and the Ga2O3 foam ceramic matrix. Through in-situ diffusion and reactive sintering, the reinforcing phase is uniformly distributed within the skeleton support and forms a stable chemical bond with the Ga2O3 matrix. This strong interfacial structure greatly improves the pull-out resistance and load transfer efficiency of the reinforcing phase, effectively resisting fluid erosion and thermal stress impacts under service conditions. It prevents brittle fracture of the skeleton and decline in load-bearing capacity caused by debonding, pull-out, or loss of the reinforcing phase, thus fundamentally ensuring the overall structural safety of the foam ceramic and guaranteeing its long-term stable operation under complex working conditions.

[0016] Fourth, maintain a highly interconnected porous topology to ensure rapid diffusion channels for pollutants. During the sintering and densification process, maintain the structural integrity of the three-dimensional interconnected porous framework, ensuring a pore connectivity rate greater than 60%, thus providing efficient channels for the rapid diffusion of pollutant molecules.

[0017] Fifth, retaining the highly active β-phase crystal facets and constructing heterojunctions broadens the photoresponse range and improves quantum efficiency. This maintains and fully utilizes the photocatalytic activity of Ga2O3, ensuring a high retention ratio of the β-phase Ga2O3 photocatalytic active phase; simultaneously, by constructing heterojunctions with narrow-bandgap photocatalytic active components, the photoresponse range is broadened, enhancing the overall utilization efficiency of sunlight.

[0018] Sixth, in-situ construction of specific active interfaces enables efficient mineralization of recalcitrant pollutants. During sintering, the components construct band-matched heterojunction interfaces or generate photocatalytically active new phases in situ through solid-phase diffusion and interfacial reactions. The electronic structure of these heterojunction interfaces or photocatalytically active new phases precisely matches the molecular characteristics of the target pollutants, especially persistent organic pollutants with high CF bond energies such as perfluorinated and polyfluoroalkyl substances, significantly improving the separation efficiency of photogenerated carriers and the activity of interfacial reactions. Simultaneously, controlled sintering heat treatment suppresses excessive coarsening of Ga2O3 grains and optimizes the high-activity (-201) crystals in the monoclinic space group C2 / m of Ga2O3. By adjusting the exposure ratio of the anisotropic crystal facets, the built-in electric field formed by the anisotropic crystal structure of Ga2O3 and the built-in electric field synergistically constructed with the heterojunction interface are utilized to maximize the directional separation efficiency of photogenerated carriers and surface reactivity. While retaining the intrinsic advantage of Ga2O3's high hole oxidation potential of approximately +3.5V to +4.0V relative to the standard hydrogen electrode, a high proportion of the thermodynamically stable active phase of Ga2O3 is ensured. This enables Ga2O3 foam ceramics to achieve specific and efficient degradation of target pollutants while possessing excellent mechanical strength and high photocatalytic activity.

[0019] During sintering, based on the chemical properties of the reinforcing phase, the interfacial bonding exhibits two forms: Firstly, for chemically inert reinforcing phases, including glass fiber and basalt fiber, they do not undergo significant chemical reactions with the foam ceramic matrix. The reinforcing effect is mainly achieved through surface microstructure anchoring and physical integration. Secondly, for the active enhancement phase, including silicon carbide whiskers, aluminum borate whiskers, magnesium borate whiskers, etc., it undergoes an in-situ reaction with the Ga2O3 matrix or photocatalytic functional phase at high temperature to form a chemical bonding layer at the interface. The thickness of the chemical bonding layer is controlled within the range of 0.01μm to 5μm to ensure that high interfacial bonding strength is obtained while avoiding thermal stress cracking caused by thermal expansion coefficient mismatch. The crystal phase composition of the monolithic gallium oxide-based photocatalytic foam ceramic is determined by the sintering reaction of the raw material powder used in the preparation step. Its phases include the unreacted original phase and / or the new crystal phase generated in situ during the sintering process. When there are two or more photocatalytic functional phases with different crystal structures or chemical compositions in the ceramic, their phase interfaces can form a heterojunction structure, which provides a built-in electric field driving force for the directional separation of photogenerated electron-hole pairs, thereby significantly improving the photocatalytic efficiency. This application also provides a monolithic gallium oxide-based photocatalytic foam ceramic prepared by the above preparation method. The monolithic gallium oxide-based photocatalytic foam ceramic has the following performance indicators: compressive strength greater than or equal to 0.5 MPa, porosity of 60% to 95%, pore structure connectivity greater than 60%, and degradation rate of organic pollutants greater than 80%.

[0020] This application also provides applications of the aforementioned monolithic gallium oxide-based photocatalytic foam ceramic, specifically including: i) applications in the degradation of organic pollutants or water treatment; ii) applications in devices for preparing devices for degrading organic pollutants or water treatment devices. The organic pollutants include those listed in the "Shanghai Key Controlled New Pollutants List (2023 Edition)," particularly perfluorinated and polyfluoroalkyl substances, antibiotics, endocrine disruptors, and other persistent organic pollutants. Perfluorooctyl sulfonic acid and its salts and perfluorooctyl sulfonyl fluoride (PFOS class); Perfluorooctanoic acid and its salts and related compounds (PFOA class); Decabromodiphenyl ether; Short-chain chlorinated paraffins; Hexachlorobutadiene; Pentachlorophenol and its salts and esters; Trichlorfon; Perfluorohexyl sulfonic acid and its salts and related compounds (PFHxS class); Declone and its cis and trans isomers; Dichloromethane; chloroform; Nonylphenol; Antibiotics (antibacterial drugs); New pollutants that have been phased out (such as anticides and cypermethrin); Microplastics; Bisphenol A.

[0021] This application provides a method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement and its application in water treatment and environmental purification. The key technical points are: using gallium oxide powder as the main raw material, supplemented with an appropriate amount of defect control agents, including high-valence metal oxides such as Nb₂O₅, Ta₂O₅, SnO₂, GeO₂, and SiO₂, and rare earth oxides such as Y₂O₃ and La₂O₃; and effectively suppressing Ga³⁺ degradation during high-temperature sintering by synergistically regulating grain growth and defect structure through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization prevent the excessive generation of oxygen vacancies, maintaining the Ga2O3 grain size within a small range and thus preserving the high specific surface area required for photocatalytic activity. Simultaneously, an appropriate amount of sintering aid is introduced, selected from one or more of ZnO, Bi2O3, SiO2, Al2O3, In2O3, MgO, and B2O3. Through liquid-phase assisted sintering or solid-phase activation mechanisms, the densification temperature of the Ga2O3 ceramic is effectively reduced, ensuring structural strength while avoiding over-sintering. Furthermore, high aspect ratio whiskers or fibers are introduced in situ to construct a three-dimensional interlocking reinforcement network; this allows the photocatalytic active component and the gallium oxide framework to form a photocatalytic functional phase network in situ through solid-phase diffusion and interfacial reactions, effectively avoiding the problem of active component detachment caused by traditional physical coating methods.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1) The introduction of a "multi-mechanism synergistic enhancement" strategy resolves the contradiction between the strength and activity of monolithic catalysts. This invention overcomes the limitations of existing technologies (such as BiVO4-based foam ceramics), which rely solely on physical loads, resulting in weak bonding and low strength. It proposes a multi-mechanism synergistic enhancement design. On one hand, by introducing fiber / whisker reinforcement phases to construct a three-dimensional interlocking network, the mechanical strength of the foam ceramic is significantly improved, solving the intrinsic brittleness problem of ceramic materials. On the other hand, through the grain boundary segregation and solid solution substitution mechanisms of defect control agents (such as high-valence oxides and rare-earth oxides), the volatilization of gallium oxide and abnormal grain growth during high-temperature sintering are effectively suppressed. This synergistic effect enables the material to maintain high porosity and mass transfer efficiency while achieving microstructural densification and a significant improvement in macroscopic mechanical properties, completely solving the technical bottlenecks of active component shedding and secondary pollution.

[0023] 2) By constructing S-shaped heterojunctions and performing defect engineering, targeted and efficient mineralization of stubborn pollutants was achieved. To address the challenges of insufficient oxidation capacity and poor degradation of persistent pollutants such as perfluorinated and polyfluorinated alkyl substances (PFAS) by existing visible-light photocatalysts such as BiVO4, this invention utilizes high-energy photogenerated holes (+3.5~+4.0 V vs. NHE) generated by the ultrawide bandgap of gallium oxide (Ga2O3), combined with in-situ constructed S-type heterojunction systems (such as Ga2O3 / ZnGa2O4, Ga2O3 / In2O3, etc.). Through bandgap engineering and defect modulation, this system not only broadens the spectral response range but, more importantly, retains the superior oxidation capacity of gallium oxide. The built-in electric field-driven charge transfer mechanism generates high concentrations of reactive oxygen species, achieving highly efficient removal of PFAS and other recalcitrant organic pollutants with extremely high CF bond energies (~485 kJ / mol), from molecular bond breaking to complete mineralization. The degradation efficiency far exceeds that of existing visible-light photocatalytic systems such as bismuth vanadate.

[0024] 3) Possesses excellent engineering applicability and environmental stability, meeting the needs of industrial water treatment. The monolithic gallium oxide-based photocatalytic foam ceramic prepared by this invention features customizable shape and easy modular assembly. Its three-dimensional interconnected porous structure not only exhibits low fluid resistance, facilitating rapid diffusion and adsorption of pollutants, but also significantly improves photon utilization through light scattering. Furthermore, this material demonstrates excellent chemical stability under extreme pH environments and strong oxidizing conditions, overcoming the shortcomings of materials such as BiVO4, which are prone to photocorrosion under strong acids and alkalis. The product of this invention eliminates the need for cumbersome solid-liquid separation processes and can be directly applied to fixed-bed or fluidized-bed reactors, combining environmental friendliness with engineering practicality, providing strong technical support for the treatment of recalcitrant new pollutants.

[0025] Specific description of application areas The monolithic gallium oxide-based photocatalytic foam ceramic described in this application is particularly suitable for degrading organic pollutants listed in the "List of Key New Pollutants under Control (2023 Edition)," including but not limited to: persistent organic pollutants such as perfluorooctane sulfonic acid and its salts and perfluorooctane sulfonyl fluoride (PFOS), perfluorooctanoic acid and its salts and related compounds (PFOA); antibiotic pollutants such as tetracycline, chlortetracycline, and oxytetracycline; and endocrine disruptors such as bisphenol A. Attached Figure Description

[0026] Figure 1 This is a process flow diagram for the preparation of monolithic gallium oxide-based photocatalytic foam ceramics. Detailed Implementation

[0027] To make the technical solution of this application clearer and easier to understand, preferred embodiments are described in detail below with reference to the accompanying drawings.

[0028] Unless otherwise specified, the experimental or testing methods described in the following examples are conventional methods; the reagents and materials described are of analytical grade and obtained from conventional commercial sources unless otherwise specified.

[0029] This application provides a method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement, comprising the following steps: Step S1: Preparation of gallium oxide-based composite paste Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a gallium oxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a gallium oxide-based composite slurry; Step S2: Preparation of gallium oxide-based foam ceramic wet blank The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and the excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank. Step S3: Prepare gallium oxide-based foam ceramic preform The gallium oxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic green body with a three-dimensional interconnected pore structure. Step S4: Sintering and Heterogeneous Structure Construction The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, defect control agents suppress Ga³⁺ during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization loss, excessive oxygen vacancy generation, lattice distortion, and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. At the same time, the defect structure and photoelectronic properties of the material are precisely regulated. The photocatalytic active component constructs a photocatalytic functional heterojunction system with the gallium oxide matrix through in-situ solid-phase reaction, which enhances the separation efficiency of photogenerated carriers and achieves efficient targeted degradation of target pollutants.

[0030] The following description, in conjunction with specific embodiments, illustrates this point.

[0031] Example 1 A method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement includes the following steps: S1: Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a gallium oxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a gallium oxide-based composite slurry; S2: The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank. S3: The gallium oxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic green body with a three-dimensional interconnected pore structure; S4: The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, defect control agents suppress Ga³⁺ during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization loss, excessive oxygen vacancy generation, lattice distortion, and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. At the same time, the defect structure and photoelectronic properties of the material are precisely regulated. The photocatalytic active component constructs a photocatalytic functional heterojunction system with the gallium oxide matrix through in-situ solid-phase reaction, which enhances the separation efficiency of photogenerated carriers and achieves efficient targeted degradation of target pollutants.

[0032] In step S1, the gallium oxide powder is a β-Ga2O3 phase powder with a purity > 98 wt.% and an average particle size D50 of 1.5 μm; The photocatalytic active component is zinc oxide (ZnO) with a purity >98 wt.%, an average particle size D50 of 0.6 μm, and an addition amount of 60 wt.% of the Ga2O3 powder mass. The sintering aid is calcium carbonate (CaCO3) with a purity >98 wt.%, an average particle size D50 of 1 μm, and an addition amount of 8 wt.% of the Ga2O3 powder mass. The defect control agent is aluminum oxide (Al2O3) with a purity >98 wt.%, an average particle size D50 of 0.7 μm, and an addition amount of 6 wt.% of the Ga2O3 powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is polyethylene glycol (PEG, molecular weight 200-20,000); the plasticizer is dioctyl sebacate (DOS); the dispersant is polymaleic anhydride (PMA); the surfactant is a fluorocarbon surfactant (Capstone® FS-30); the rheology modifier is polyacrylamide (PAM); and the defoamer is isooctyl alcohol (IOA). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is silicon carbide whiskers with an average length of 15 μm and an average diameter of 0.6 μm; The gallium oxide-based composite slurry has a solid content of 50 vol.% and a pH of 10. The addition amounts of each component of the organic additive and the reinforcing phase are based on the total mass of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents, specifically as follows: binder, 2.5 wt.%; dispersant, 1.6 wt.%; plasticizer, 3.2 wt.%; surfactant, 0.5 wt.%; rheology modifier, 2.9 wt.%; defoamer, 1.3 wt.%; reinforcing phase, 25 wt.%. In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the gallium oxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring rate was 1500 rpm; the stirring time was 15 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the gallium oxide-based suspension slurry and the composite slurry was 1500 rpm; the stirring time was 300 min; the stirring paddle was made of polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a macroscopic shape of cuboid. The impregnation is carried out under normal pressure; the impregnation process is carried out at 25°C for 250 seconds. The pressure of the extrusion desizing is controlled within 1 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After four cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 480% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 25°C, a relative humidity of 20%, a ventilation rate of 1 m / s, and a natural air drying time of 12 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 75°C at a rate of 8°C / min, and the temperature is maintained for 4 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature is increased to 250℃ at a rate of 10℃ / min and held for 20 min. The second stage involves raising the temperature to 450℃ at a rate of 4℃ / min and holding it for 10 minutes. The third stage involves increasing the temperature to 600℃ at a rate of 2℃ / min and holding it for 5 minutes. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 1450℃, constant temperature time 5min, and heating rate 10℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Thermal decomposition and liquid-phase activation reaction of sintering aids The sintering aid, calcium carbonate (CaCO3), is an alkaline earth metal carbonate-type precursor sintering aid. The decomposition initiation temperature of CaCO3 is approximately 840 °C, and in this embodiment, complete decomposition is achieved at approximately 900 °C, generating highly active nano-sized CaO particles and CO2 gas. CaCO3 → CaO + CO2↑ [In-situ thermal decomposition, ≈900 °C] The generated CaO exhibits extremely high chemical activity, rapidly undergoing a solid-state reaction at the interface with surrounding Ga2O3 particles to form a calcium-gallium composite oxide grain boundary activated phase. CaO + Ga₂O₃ → CaGa₂O₄ [Monoclinic calcium gallate, grain boundary activated phase, ≈1000-1200 °C] The CaGa2O4 phase (monoclinic, space group C2 / c) forms a eutectic system with Ga2O3 in the 1200-1300 °C range (eutectic point approximately 1280 °C). During the heating process to 1450 °C, a Ca-Ga-rich transient liquid phase forms at the particle interface. During the 1450 °C holding stage, the CaGa2O4 liquid phase exhibits excellent wettability, driving the rearrangement of Ga2O3 and ZnO particles through capillary forces. The width of the neck connection region between particles is precisely controlled within 10 μm, significantly accelerating the densification process of the three-dimensional skeleton network and ensuring the structural integrity of the foam ceramic skeleton.

[0033] (2) Equivalent solid solution substitution of defect control agents and grain boundary stabilization reaction The defect control agent, aluminum oxide (Al₂O₃), is an equivalent substitution stabilizer. β-Ga₂O₃ has a monoclinic crystal structure (space group C² / m) and contains two types of Ga³. + Lattice sites: tetrahedral coordinated Ga(I) sites (rtet = 0.062 nm) and octahedral coordinated Ga(II) sites (roct = 0.076 nm). Al³ + With an ionic radius of 0.0535 nm (tetracoordinate), and a size difference of approximately 14% from the Ga(I) site, it preferentially occupies the tetrahedral Ga(I) lattice site. Through an equivalent substitution mechanism, Al³⁺… + Solid solution enters the β-Ga₂O₃ lattice to form (Ga 2-x Al x O3 continuous solid solution: Al³ + Replace Ga³ + (I) → (Ga 2-x Al x O3 [equivalent substitution, neutral defect AlGa×, 1450 °C] Al³ + The equivalent substitution does not introduce additional charge imbalance. Given that the Al-O bond energy (approximately 512 kJ / mol) is significantly higher than the Ga-O bond energy (approximately 374 kJ / mol), this mechanism intrinsically strengthens the lattice binding energy of β-Ga₂O₃, thereby thermodynamically suppressing the Ga³⁺ reaction during high-temperature sintering. + →Ga 0Excessive reduction and Ga2O vapor generation. When the Al2O3 addition (6 wt%) exceeds the solid solution limit of the β-Ga2O3 lattice, supersaturated Al³⁺... + The excess aluminum component is enriched at the grain boundaries via grain boundary segregation. Due to the limited solid solubility of Al₂O₃ in β-Ga₂O₃ at high temperatures, the excess aluminum component precipitates in situ at the grain boundaries as a high-melting-point aluminum-rich second phase (mainly α-Al₂O₃). Al₂O₃(excess) → α-Al₂O₃ [grain boundary precipitation, grain boundary pinning phase, 1450 °C] The generated nanoscale α-Al₂O₃ (corundum structure, Eg ≈ 8.8 eV) is continuously distributed at the grain boundaries of β-Ga₂O₃ grains in the form of thin films or discrete particles. These high-melting-point second-phase particles exert a drag force on grain boundary migration through the Zener pinning mechanism, effectively suppressing the abnormal growth of β-Ga₂O₃ grains and reducing the average grain size D. 50 The synergistic control is kept within 3 μm, thereby maintaining a high specific surface area and photocatalytic active site density of the foam ceramic skeleton.

[0034] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The silicon carbide (SiC) whiskers used as the reinforcing phase exhibit strong chemical stability and belong to an inert-active composite reinforcing phase. Under sintering conditions of 1450°C in air atmosphere, slight controllable oxidation occurs on the whisker surface, forming a continuous dense SiO2 passivation film with a thickness of approximately 2-8 nm on the whisker surface. SiC(s) + O2(g) → SiO2(s) + CO2(g) [1450 °C, air, slightly controlled] Under the synergistic effect of high temperature (1450 °C) and liquid phase (CaGa2O4), the SiO2 passivation film formed undergoes an in-situ interfacial reaction on the whisker surface, generating a gallium silicate chemical bond layer: SiO2 + Ga2O3 → Ga2SiO5 [β-gallium silicate, interfacial bonded phase, 1450 °C] The generated Ga2SiO5 (β-gallium silicate, monoclinic crystal system, Eg ≈ 5.5 eV) forms a continuous chemically bonded interface layer with a thickness of about 5-20 nm at the interface between SiC whiskers and Ga2O3 matrix, upgrading the bonding mode between whiskers and matrix from physical contact to chemical bonding. The excellent mechanical properties of SiC whiskers (elastic modulus of about 480 GPa, flexural strength of about 800 MPa) provide a high modulus load transfer path for foam ceramic skeleton ribs, significantly improving compressive strength and crack propagation resistance, ensuring structural reliability under actual water treatment conditions.

[0035] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytically active component, zinc oxide (ZnO), undergoes an interfacial reaction with Ga2O3 via solid-phase diffusion during sintering at 1450 °C. + Diffusion towards the interface of Ga2O3 particles, Ga³ + Reverse diffusion towards the ZnO particle interface leads to the in-situ generation of a new photocatalytically active zinc-gallium composite oxide phase at the two-phase contact interface. ZnO + Ga2O3 → ZnGa2O4 [spinel zinc gallate, 1450 °C] The generated ZnGa2O4 has a spinel (AB2O4) crystal structure, Zn² + Occupying a tetrahedral lattice, Ga³ + Occupying octahedral sites, the band gap is approximately 4.4-4.6 eV (deep ultraviolet response, λ < 270-280 nm), the conduction band position is approximately -0.9 eV (vs NHE), and the valence band position is approximately +3.6 eV (vs NHE). Due to the extremely short holding time (only 5 min) at the sintering temperature of 1450 °C in this embodiment, solid-phase diffusion is kinetically limited. The new ZnGa2O4 phase is mainly enriched in the form of nanoscale thin films at the interface between ZnO and Ga2O3 particles. A large amount of unreacted Ga2O3 phase remains in its original crystal structure with the ZnO phase, jointly participating in the construction of the photocatalytic functional phase network.

[0036] (5) Heterogeneous structure construction and PFOS targeted degradation mechanism The ZnGa2O4 generated in situ during the controlled sintering heat treatment process, together with the residual Ga2O3 phase and ZnO phase, jointly construct a Ga2O3 / ZnO / ZnGa2O4 deep ultraviolet S-scheme heterojunction system. (1) Ga2O3 (OP, oxidation-type photocatalyst): Conduction band position is approximately -0.7 eV (vs NHE), valence band position is approximately +4.1 eV (vs NHE), and band gap is approximately 4.8 eV (λ<260 nm, deep ultraviolet response). Its valence band holes have super strong oxidizing power (potential far exceeding the CF / CS bond oxidation threshold), which is the core thermodynamic driving force for PFAS degradation; because its conduction band potential is relatively positive, its reducing ability is relatively weak, and photogenerated electrons are easily recombinated; (2) ZnO (RP, reduced photocatalyst): Conduction band position is approximately -0.5 eV (vs NHE), valence band position is approximately +2.9 eV (vs NHE), and band gap is approximately 3.4 eV (UV activity). Its conduction band electrons have strong reducing properties and can drive the generation of O2·O2. - Superoxide radicals; due to their shallow valence band potential (+2.9 eV), their oxidizing power is insufficient to efficiently break CF bonds, and photogenerated holes are easily recombinated. (3) ZnGa2O4 (band-bridged intermediate phase): The conduction band position is approximately -0.9 eV (vs NHE), the valence band position is approximately +3.6 eV (vs NHE), the band gap is approximately 4.5 eV, and the band position is between Ga2O3 and ZnO, forming a band gradient bridging structure. In the S-type heterojunction mechanism, the built-in electric field drives the weakly oxidizing holes (+2.9 eV) of the ZnO valence band and the weakly reducing electrons (-0.7 eV) of the Ga2O3 conduction band to recombine and annihilate in a directional manner at the ZnGa2O4 bridging interface. At the same time, the highly oxidizing valence band holes (+4.1 eV) of Ga2O3 are retained to efficiently attack the CS / CF bonds, and the strongly reducing conduction band electrons (-0.5 eV) of ZnO are efficiently used to generate O2. - This enables the synergistic and efficient supply of dual active species.

[0037] The above system is effective against the target pollutant perfluorooctyl sulfonic acid (PFOS, C8F). 17 SO3 - The targeted degradation of PFOS (MW = 538.22 g / mol) is based on the precise matching between the bond energy characteristics of the PFOS molecule and the ultra-strong oxidizing power of Ga2O3. The PFOS molecule is a perfluorooctyl chain (C8F) composed of seven -CF2- repeating units and a terminal -CF3 group. 17 -), and the terminal sulfonic acid group (-SO3) - The system is composed of [missing information - likely a specific chemical group or structure]. The bond energies and breaking priorities of the key chemical bonds are as follows: the sulfonic acid group CS bond has a bond energy of approximately 270-290 kJ / mol, which is the lowest bond energy site in the entire molecule and is the core target site preferentially attacked by Ga2O3's strong valence band holes; the C-CF3 terminal CC bond (approximately 347 kJ / mol) is next; the CF bond (approximately 485 kJ / mol) has the highest bond energy and requires the cooperation of Ga2O3 deep ultraviolet photons and strong holes to achieve gradual breaking. Based on this, the targeted degradation of PFOS by the system proceeds in three steps: (1) Targeted initiation (CS bond breaking and sulfonic acid group removal): The super-strong oxidizing hole (+4.1 eV) in the valence band of Ga2O3 directly attacks the CS bond of the sulfonic acid group in the PFOS molecule (270-290 kJ / mol), inducing single-electron oxidation, and removing -SO3 - The radical is removed in the form of SO3, generating a perfluorooctyl radical (C8F). 17 •); Sulfonate ions are then further oxidized to SO4². - Simultaneous release; the high quantum energy of deep ultraviolet photons (hν≥4.8 eV) can also directly photoexcite the CS bonds in PFOS, synergistically promoting the rapid removal of sulfonic acid groups; (2) Gradual CF bond breaking and chain shortening (defluorination stage): perfluorooctyl radical (C8F) 17• Under the synergistic effect of Ga2O3's strong valence band holes (+4.1 eV) and deep ultraviolet photons, a stepwise oxidative defluorination process is carried out; each oxidation removes one F. - The terminal group -CF3 is gradually converted to -CF2•→-COF→-COOH→CO2; at the same time, the conduction band electrons of ZnO generate ·O2. - Cooperative attack on progressively shortening perfluorocarbon chain intermediates accelerates chain shortening; F - It is released into the water in ionic form and can be recovered through ion exchange resin; (3) Complete defluorination and mineralization: After stepwise defluorination, PFOS is degraded into short-chain perfluorocarboxylic acids (such as CF3COOH) and short-chain intermediates such as fluoroacetic acid; the high-energy holes generated by the Ga2O3 deep ultraviolet photocatalytic system and ·O2 - The ·OH group works synergistically to continuously attack short-chain fluorinated organic acids, overcoming the high bond energy barrier of the CF bond (485 kJ / mol), ultimately mineralizing all carbon chains into CO2 and H2O, and releasing all F. - This enables the complete degradation of PFOS from the removal of sulfonic acid groups, the gradual defluorination to full mineralization.

[0038] The specificity of the targeted matching stems from the precise match between the strong valence band hole of Ga2O3 (+4.1 eV) and the lowest bond energy of the CS bond of PFOS sulfonic acid group (270-290 kJ / mol), as well as the quantum energy advantage of the direct photoactivation of CF bond by deep ultraviolet high-energy photons (hν≥4.8 eV). The ZnGa2O4 bridging phase simultaneously retains the strong oxidation hole of Ga2O3 (+4.1 eV) and the strong reduction conduction band electron of ZnO (-0.5 eV) through the S-type heterojunction mechanism, and realizes the efficient and complete degradation of PFOS from CS bond targeted initiation, stepwise defluorination to complete mineralization under deep ultraviolet light driving.

[0039] The monolithic gallium oxide-based photocatalytic foam ceramic has a cuboid macroscopic shape; compressive strength ≥ 0.3 MPa, porosity ≥ 85%, pore structure connectivity ≥ 80%, and a degradation rate of perfluorooctanesulfonic acid (PFOS) ≥ 90% under deep ultraviolet light irradiation; Those skilled in the art can determine the process window that satisfies the above-mentioned effects through limited experiments under conventional equipment conditions, based on the specific type of gallium oxide powder, the type of photocatalytically active component, and the characteristics of the reinforcing phase.

[0040] Example 2 A method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement includes the following steps: S1: Add organic additives and pH adjusters to deionized water and disperse them evenly to form a homogeneous solution; add gallium oxide powder, photocatalytic active components, sintering aids and defect control agents to the solution in batches and disperse them evenly to form a gallium oxide-based suspension slurry; add fiber and / or whisker reinforcing phase to the suspension slurry and disperse it evenly to form a gallium oxide-based composite slurry.

[0041] S2: The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank.

[0042] S3: The gallium oxide-based foam ceramic wet blank obtained in step S2 is first naturally air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried wet blank is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic blank with a three-dimensional interconnected pore structure.

[0043] S4: The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, defect control agents suppress Ga³⁺ during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization loss, excessive oxygen vacancy generation, lattice distortion, and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. At the same time, the defect structure and photoelectronic properties of the material are precisely regulated. The photocatalytic active component constructs a photocatalytic functional heterojunction system with the gallium oxide matrix through in-situ solid-phase reaction, which enhances the separation efficiency of photogenerated carriers and achieves efficient targeted degradation of target pollutants.

[0044] In step S1, the gallium oxide powder is a β-Ga2O3 phase powder with a purity > 98 wt.% and an average particle size D50 of 1.5 μm; The photocatalytic active component is indium trioxide (In₂O₃), with a purity >98 wt.%, an average particle size D50 of 0.8 μm, and an addition amount of 60 wt.% of the Ga₂O₃ powder mass. The sintering aid is tin dioxide (SnO2) with a purity >98 wt.%, an average particle size D50 of 1.5 μm, and an addition amount of 10 wt.% of the Ga2O3 powder mass. The defect control agent is hafnium dioxide (HfO2) with a purity >98 wt.%, an average particle size D50 of 0.9 μm, and an addition amount of 8 wt.% of the Ga2O3 powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is polyacrylic acid (PAA); the plasticizer is glycerol (GLY); the dispersant is polycarboxylate superdispersant (Tamol™SN); the surfactant is sodium dodecyl sulfate (SDS); the rheology modifier is xanthan gum (XG); and the defoamer is silicone oil (DowCorning® 200 Fluid). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is mullite whiskers with an average length of 12 μm and an average diameter of 0.5 μm; The gallium oxide-based composite slurry has a solid content of 53 vol.% and a pH of 10. The amounts of each component of the organic additive and the reinforcing phase added are based on the total mass of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents, and are as follows: binder, 0.9 wt.%; dispersant, 3.8 wt.%; plasticizer, 1.2 wt.%; surfactant, 2.1 wt.%; rheology modifier, 0.8 wt.%; defoamer, 3.4 wt.%; reinforcing phase, 23 wt.%. In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the gallium oxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring speed was 1900 rpm; the stirring time was 6 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the gallium oxide-based suspension slurry and the composite slurry was 1500 rpm; the stirring time was 100 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a cubic shape. The impregnation is carried out under normal pressure; the impregnation process is conducted at 25°C for 120 seconds. The pressure of the extrusion desizing is controlled within 1 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After four cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 590% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 35°C, a relative humidity of 20%, a ventilation rate of 1 m / s, and a natural air drying time of 10 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 75°C at a rate of 10°C / min, and the temperature is maintained for 3 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature is increased to 250℃ at a rate of 8℃ / min and held for 10min. The second stage involves raising the temperature to 450℃ at a rate of 4℃ / min and holding it for 5 minutes. The third stage involves raising the temperature to 600℃ at a rate of 2℃ / min and holding it for 1 min. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1500 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 1500℃, constant temperature time 5min, and heating rate 10℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Activation of the eutectic liquid phase and interfacial densification reaction of sintering aids The sintering aid, tin dioxide (SnO2), has a melting point of approximately 1630 °C. In this embodiment, it exists in solid form at the sintering temperature (1500 °C) and cannot generate an intrinsic liquid phase. However, the SnO2-Ga2O3 binary system has a low eutectic point around 1450 °C, significantly lower than the melting points of each component. During the heating process to 1500 °C, a Sn-Ga eutectic activated liquid phase forms at the interface between SnO2 and Ga2O3 particles. During the 1500 °C holding stage, the wettability of the activated liquid phase increases, driving the rearrangement and densification of Ga2O3 and In2O3 particles. The width of the neck connection region between particles is precisely controlled within 10 μm, effectively promoting the formation of a continuous skeletal network structure in the foam ceramic. Simultaneously, SnO2 undergoes an in-situ solid-phase reaction with Ga2O3 and In2O3 at the interface, generating a new phase with photocatalytic activity. SnO2 + Ga2O3 → Ga2SnO5 [orthorhombic tin gallium salt, interface activated phase, 1500 °C] The generated Ga2SnO5 (orthorhombic crystal system) E (g ≈ 3.5-4.0 eV) forms an activated bonded phase at the neck interface between Ga2O3 particles, contributing to both enhanced interparticle chemical bonding and synergistic photocatalytic function; during the high-temperature holding stage, Sn 4+ It can also partially dissolve into the Ga2O3 lattice (donor doping), suppressing Ga³ energy levels through Fermi level rise. + →Ga 0 Restoration, and synergistic effect to regulate defects.

[0045] (2) Donor-type solid solution and grain boundary stabilization reaction of defect control agents The defect control agent, hafnium dioxide (HfO2), is a donor-type substitution stabilizer. 4+ The ionic radius is 0.071 nm (six-coordinated), and... β -Octahedral coordination of Ga³ in the Ga₂O₃ lattice + The size difference (0.062 nm) is approximately 14%, satisfying the solid solution substitution conditions. Hf 4+ Entering the Ga2O3 lattice and replacing Ga³ + The donor-type substitution defect Hf is formed. Ga • This donor defect raises the Fermi level of the material by releasing electrons, thereby enhancing the acceptor-type gallium vacancy defect (V'''). Ga The formation energy of HfO2 is reduced, and its concentration is decreased, while the reduction and volatilization of Ga2O3 under high temperature conditions is suppressed. When the amount of HfO2 added (8 wt%) approaches or exceeds the solid solubility limit of Ga2O3 lattice, the supersaturated HfO2... 4+ HfO2 dispersed grain boundary phase is enriched at grain boundaries through grain boundary segregation, forming a nanoscale HfO2 dispersed grain boundary phase. This second phase inhibits the abnormal growth of Ga2O3 grains at 1500 °C through the Zener pinning mechanism, resulting in a smaller average grain size. D 50 The thickness is controlled within 3 μm. At the same time, the grain boundary HfO2 phase increases the grain boundary diffusion barrier and reduces the Ga2O volatilization rate, thereby maintaining the stability of the Ga2O3 crystal structure and the high retention ratio of the photocatalytically active phase.

[0046] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The mullite (3Al2O3·2SiO2) whiskers, the reinforcing phase, are partially active reinforcing phases with a melting point of approximately 1840 °C. The main framework is chemically stable during the 1500 °C holding period. However, under the synergistic effect of the high temperature of 1500 °C and the Sn-Ga eutectic liquid phase, the SiO2 and Al2O3 components on the whisker surface undergo in-situ solid-liquid (liquid-solid) interfacial reactions with the Ga2O3 matrix, generating two types of chemically bonded phases at the whisker-matrix interface: SiO2 + Ga2O3 → Ga2SiO5 [Gallium silicate, monoclinic crystal system, 1500 °C] Al₂O₃ + Ga₂O₃ → 2(Ga,Al)O₃ [Corundum-like solid solution, interfacial bonded phase, 1500 °C] The generated Ga2SiO5 and (Ga,Al)O3 together form a continuous chemically bonded interface layer with a thickness of about 5-20 nm at the interface between the mullite whiskers and the Ga2O3 matrix, upgrading the bonding mode between the whiskers and the matrix from physical intercalation to chemical bonding, which significantly improves the interfacial shear strength. The excellent mechanical properties of the mullite whiskers provide a high-modulus load transfer path for the foam ceramic skeleton ribs, significantly improving the compressive strength and crack propagation resistance, ensuring the structural reliability under water treatment conditions.

[0047] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytically active component, indium trioxide (In₂O₃), undergoes an interfacial reaction with Ga₂O₃ via solid-phase diffusion during sintering at 1500 °C. During sintering, In³⁺… + Ions diffuse towards the interface of Ga2O3 particles, while Ga³ + Ions diffuse in reverse towards the In₂O₃ particle interface, forming a novel photocatalytically active indium gallium composite oxide phase in situ at the interface region between the two phases. In₂O₃ + Ga₂O₃ → 2InGaO₃ [Layered indium gallium oxide, 1500 °C] The resulting InGaO3 is a layered indium gallium oxide, typically belonging to the R... The material is a layered oxide structure system related to the m-space group. It has a bandgap of approximately 2.8–3.2 eV, corresponding to a visible-near-ultraviolet response. lThe InGaO3 phase has a diameter of approximately 390-440 nm. Its conduction band potential is approximately -0.6 eV (vs NHE), and its valence band potential is approximately +2.5 eV (vs NHE), exhibiting a suitable redox potential distribution. This allows it to effectively participate in the separation and migration of photogenerated electron-hole pairs, thereby enhancing the photocatalytic activity of the material system. In this embodiment, the sintering temperature is 1500 °C, and the holding time is relatively short (approximately 5 min). The interfacial reaction is mainly limited to the particle contact region. Therefore, the newly generated InGaO3 phase is primarily enriched at the interface between In2O3 and Ga2O3 particles as a nanoscale interfacial layer or thin film structure. Simultaneously, a large amount of unreacted Ga2O3 and In2O3 phases remain in the system, maintaining their original crystal structures. The resulting InGaO3–In2O3–Ga2O3 multiphase synergistic structure jointly constructs a photocatalytic functional phase network, promoting the separation of photogenerated carriers through the interfacial heterojunction effect and improving the overall photocatalytic reaction efficiency.

[0048] (5) Heterogeneous structure construction and PFOA targeted degradation mechanism The InGaO3 generated in situ during the controlled sintering heat treatment process, together with the residual Ga2O3 phase and the In2O3 phase, jointly construct a Ga2O3 / In2O3 / InGaO3 deep ultraviolet S-scheme heterojunction system. (1) Ga2O3 (OP, oxidation-type photocatalyst): conduction band position is approximately -0.7 eV (vs NHE), valence band position is approximately +4.1 eV (vs NHE), band gap is approximately 4.8 eV (deep ultraviolet response, l <260 nm). Its valence band holes have extremely strong oxidizing power (overpotential reaches +1.72 eV relative ·OH generation potential), which is an important thermodynamic driving force for the oxidative breaking of high bond energy C–F bonds; because its conduction band potential is relatively positive, its reducing power is relatively weak, and photogenerated electrons are easily recombinated; (2) In2O3 (RP, reduced photocatalyst): conduction band position is approximately -0.6 eV (vs NHE), valence band position is approximately +2.4 eV (vs NHE), band gap is approximately 3.0 eV ( l <410 nm, visible to near-ultraviolet response). Its conduction band electrons have strong reducing properties (relative to O2 / ·O2). - With an overpotential of approximately 0.27 eV, it can efficiently generate O2. - Superoxide radicals synergistically attack the carboxyl group and perfluorocarbon chain of PFOA molecules; due to their shallow valence band potential, their oxidizing power is insufficient to break the C–F bond, and photogenerated holes are easily recombinated. (3) InGaO3 (band-bridging intermediate phase): The conduction band position is approximately -0.6 eV (vs NHE), the valence band position is approximately +2.5 eV (vs NHE), and the band position is between Ga2O3 and In2O3, forming a band gradient bridging structure. In the S-type heterojunction mechanism, the built-in electric field at the InGaO3 interface drives the weakly oxidizing valence band holes (+2.4 eV) of In2O3 and the weakly reducing conduction band electrons (-0.7 eV) of Ga2O3 to recombine and annihilate in a directional manner at the InGaO3 bridging interface, while retaining the super-strong oxidizing valence band holes (+4.1 eV) of Ga2O3 and the strong reducing conduction band electrons (-0.6 eV) of In2O3, achieving a synergistic and efficient supply of dual active species.

[0049] The above system is effective against the target pollutant perfluorooctanoic acid (PFOA, C7F). 15 The targeted degradation of COOH (MW = 414.07 g / mol) is based on the precise matching of the bond energy characteristics of PFOA molecules with the ultra-strong oxidizing power of Ga2O3. The PFOA molecule is a perfluoroheptyl chain (C7F) composed of seven -CF2- linkages. 15 -) and the terminal carboxyl group (-COOH). The bond energies and breaking priorities of the key chemical bonds are as follows: the C–C bond (at the junction of -COOH and the perfluorocarbon chain) has a bond energy of approximately 360-370 kJ / mol, which is a relatively low bond energy site in the whole molecule and is the preferred starting target site for the system; the C–F bond (approximately 485 kJ / mol) has the highest bond energy and requires Ga2O3's ultra-strong hole-cooperative deep ultraviolet photons to achieve gradual breaking. Accordingly, the targeted degradation of PFOA by the system proceeds in three steps: (1) Targeted initiation (carboxyl decarboxylation degradation, chain end stripping): Ga2O3's super-oxidizing hole (+4.1 eV) directly oxidizes the terminal carboxyl group (-COOH) of the PFOA molecule, triggering a one-electron oxidative decarboxylation reaction (photo-Kolbe reaction): C7F 15 COO - + h + → C7F 15 • + CO2↑ Generates perfluoroheptyl radical (C7F) 15 •); The strong reducing electrons (-0.6 eV) in the conduction band of In2O3 drive the production of a large amount of O2·O2. - Superoxide radicals synergistically participate in the oxidative activation of carboxyl groups; due to the high quantum energy of Ga2O3 deep ultraviolet photons (hν≥4.8 eV), decarboxylation initiation can be efficiently completed in each photocatalytic cycle; (2) Gradual C–F bond breaking and chain shortening (defluorination and decarbonization stage): perfluoroheptyl radical (C7F) 15• Continuous oxidative defluorination via the C–F bond at the chain end: the terminal group -CF3 → -CF2• → -COF (acyl fluoride intermediate) → hydrolysis to generate -COOH (short-chain perfluorocarboxylic acid), achieving chain shortening (unzipping decarbonization mechanism); each shortening step releases one CO2 and one F. - , forming C6F 13 COOH→C5F 11 The stepwise degradation sequence of COOH→…→CF3COOH; Ga2O3's super-strong holes (+4.1 eV) and deep ultraviolet photons synergistically provide the energy required to overcome the high bond energy (485 kJ / mol) of the C–F bond; (3) Complete mineralization of short-chain perfluorocarboxylic acids: Short-chain perfluorocarboxylic acid intermediates such as trifluoroacetic acid (CF3COOH) are highly reactive oxidizing species in the Ga2O3 / In2O3 / InGaO3 system (high concentration of ·OH and ·O2). - Under the synergistic attack of ) and further oxidation reactions, complete mineralization is achieved, converting all organic carbon into CO2, while releasing all F - This enables the complete residue-free degradation of PFOA, from decarboxylation initiation and stepwise chain shortening to defluorination and complete mineralization.

[0050] The specificity of the targeted matching originates from the direct oxidation matching between the strong valence band hole (+4.1 eV) of Ga2O3 and the C–COOH bond of PFOA carboxyl group, as well as the quantum energy advantage of the direct photoactivation of C–F bond by deep ultraviolet photons; the S-type heterojunction mechanism simultaneously retains the strong oxidation hole (+4.1 eV) of Ga2O3 and the strong reduction conduction band electron (-0.6 eV) of In2O3, achieving efficient and gradual degradation and complete mineralization of PFOA throughout the entire process under the synergistic drive of deep ultraviolet and ultraviolet light.

[0051] The monolithic gallium oxide-based photocatalytic foam ceramic has a cubic shape; compressive strength ≥ 0.4 MPa, porosity ≥ 86%, pore structure connectivity ≥ 90%, and a perfluorooctanoic acid (PFOA) degradation rate ≥ 92% under deep ultraviolet light irradiation; Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of gallium oxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0052] Example 3 A method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement includes the following steps: S1: Add organic additives and pH adjusters to deionized water and disperse them evenly to form a homogeneous solution; add gallium oxide powder, photocatalytic active components, sintering aids and defect control agents to the solution in batches and disperse them evenly to form a gallium oxide-based suspension slurry; add fiber and / or whisker reinforcing phase to the suspension slurry and disperse it evenly to form a gallium oxide-based composite slurry.

[0053] S2: The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank.

[0054] S3: The gallium oxide-based foam ceramic wet blank obtained in step S2 is first naturally air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried wet blank is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic blank with a three-dimensional interconnected pore structure.

[0055] S4: The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, defect control agents suppress Ga³⁺ during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization loss, excessive oxygen vacancy generation, lattice distortion, and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. At the same time, the defect structure and photoelectronic properties of the material are precisely regulated. The photocatalytic active component constructs a photocatalytic functional heterojunction system with the gallium oxide matrix through in-situ solid-phase reaction, which enhances the separation efficiency of photogenerated carriers and achieves efficient targeted degradation of target pollutants.

[0056] In step S1, the gallium oxide powder is a β-Ga2O3 phase powder with a purity > 98 wt.% and an average particle size D50 of 1.5 μm; The photocatalytic active component is tungsten trioxide (WO3) with a purity >98 wt.%, an average particle size D50 of 0.3 μm, and an addition amount of 60 wt.% of the Ga2O3 powder mass. The sintering aid is lanthanum oxide (La₂O₃) with a purity >98 wt.%, an average particle size D50 of 2 μm, and an addition amount of 7 wt.% of the Ga₂O₃ powder mass. The defect control agent is magnesium oxide (MgO) with a purity >98 wt.%, an average particle size D50 of 0.7 μm, and an addition amount of 5 wt.% of the Ga2O3 powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is polyvinyl acetate (PVAc); the plasticizer is epoxidized soybean oil (ESO); the dispersant is ammonium polyacrylate (NH4PAA); the surfactant is cetyltrimethylammonium bromide (CTAB); the rheology modifier is sodium carboxymethyl cellulose (CMC); and the defoamer is n-octanol (NOA). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase consists of aluminum borate whiskers and silicon carbide fibers; wherein the aluminum borate whiskers have an average length of 17 μm and an average diameter of 0.5 μm; and the silicon carbide fibers have an average length of 3 μm and an average diameter of 0.3 μm. The gallium oxide-based composite slurry has a solid content of 55 vol.% and a pH of 10. The amounts of each component of the organic additive and the reinforcing phase are based on the total mass of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents, and are as follows: binder, 3.7 wt.%; dispersant, 0.6 wt.%; plasticizer, 2.9 wt.%; surfactant, 1.4 wt.%; rheology modifier, 3.3 wt.%; defoamer, 0.9 wt.%; reinforcing phase, aluminum borate 15 wt.% and silicon carbide fiber 15 wt.%. In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the gallium oxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring rate was 1900 rpm; the stirring time was 10 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the gallium oxide-based suspension slurry and the composite slurry was 2100 rpm; the stirring time was 120 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a cylindrical shape. The impregnation is carried out under normal pressure; the impregnation process is conducted at 25°C for 120 seconds. The pressure of the extrusion desizing is controlled within 1 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After four cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 510% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 35°C, a relative humidity of 20%, a ventilation rate of 1 m / s, and a natural air drying time of 12 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 75°C at a rate of 10°C / min, and the temperature is maintained for 3 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature was increased to 250℃ at a rate of 6℃ / min and held for 20 min. The second stage involves raising the temperature to 450℃ at a rate of 3℃ / min and holding it for 10 minutes. The third stage involves increasing the temperature to 600℃ at a rate of 2℃ / min and holding it for 5 minutes. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 1100℃, isothermal time 1min, and heating rate 15℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Liquid-phase assisted sintering and interfacial activation reaction of sintering aids The sintering aid, lanthanum trioxide (La₂O₃), is a rare earth oxide sintering aid. + The ionic radius (0.116 nm) is much larger than that of Ga³. + (0.062 nm), with extremely low solid solubility in the Ga2O3 lattice, mainly segregates to the Ga2O3 grain boundaries, forming a rare-earth gallium composite oxide grain boundary phase. Through liquid-phase assisted sintering and grain boundary pinning mechanisms, it simultaneously plays a role in sintering aid and grain growth inhibition. During the 1100 °C high-temperature holding stage, La2O3 and Ga2O3 undergo a solid-state reaction at the grain boundaries, generating a lanthanum-gallium composite oxide grain boundary activation phase. La₂O₃ + Ga₂O₃ → 2LaGaO₃ [Perovskite-type lanthanum gallate, grain boundary phase, 1100 °C] The resulting LaGaO3 phase (perovskite structure, orthorhombic crystal system) E The LaGaO3 grain boundary phase (g ≈ 5.6 eV) is enriched at the grain boundaries of Ga2O3 and WO3 particles. Through the transient liquid-assisted mass transfer mechanism at the grain boundaries, it drives particle rearrangement, promotes neck connection between particles (neck width controlled within 10 μm), and ensures the structural integrity of the foam ceramic skeleton rib network. At the same time, the LaGaO3 grain boundary phase effectively inhibits the abnormal growth of Ga2O3 and WO3 grains at 1100 °C through the solute drag effect, maintains a high specific surface area of ​​the skeleton, and provides microstructure protection for the high-density distribution of subsequent photocatalytic active sites.

[0057] (2) Acceptor-type solid solution and grain boundary pinning stabilization reaction of defect control agents The defect control agent, magnesium oxide (MgO), is an acceptor-type substitution stabilizer. Mg²⁺ + The ionic radius is 0.072 nm (six-coordinated), and... β -Ga₂O₃ octahedral coordination of Ga³ + (0.062 nm) Similar in size but with a certain mismatch (approximately 16%), it can partially dissolve into the Ga2O3 lattice, forming MgGa′ acceptor-type substitution defects (net negative charge -1): Mg² + Replace Ga³ + → MgGa′ [Acceptor defect, Fermi level decreases] Mg Ga Acceptor-type defects reduce the intensity of donor-type intrinsic defects (such as oxygen vacancies) by lowering the Fermi level of the system. O •• Ga interstitial Ga i ••• The equilibrium concentration of Ga2O3 is thermodynamically controlled to regulate the defect structure equilibrium and maintain its balance. β -The photocatalytic active phase structure stability of Ga2O3. When the amount of MgO added (5 wt%) exceeds the upper limit of solid solubility, the supersaturated Mg²⁺... + Spinel-type magnesium gallate pinning phases are generated in situ at grain boundaries via a grain boundary segregation mechanism with Ga2O3: MgO + Ga2O3 → MgGa2O4 [spinel-type magnesium gallate, grain boundary pinned phase, 1100 °C] The generated MgGa2O4 (spinel type, E(g ≈ 4.7 eV) A ​​continuous nanoscale pinning layer is formed at the grain boundaries of Ga2O3 grains, which effectively suppresses abnormal growth of Ga2O3 grains through the Zener pinning mechanism, thereby reducing the average grain size of Ga2O3. D 50 The diameter is controlled within 5 μm to maintain the high specific surface area of ​​the foam ceramic skeleton.

[0058] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The reinforcing phase is composed of aluminum borate whiskers (Al). 18 B4O 33 It is composed of silicon carbide fiber (SiC) and silicon carbide fiber, and the two exhibit different interfacial bonding mechanisms during sintering at 1100 °C: Aluminum borate whiskers (Al) 18 B4O 33 This belongs to the active enhancement phase. The B2O3 component (melting point approximately 450 °C) on the whisker surface diffuses into the Ga2O3 matrix interface in liquid phase form, undergoing an in-situ liquid-solid interface reaction with Ga2O3 to form a gallium borate chemically bonded layer. B₂O₃(l) + Ga₂O₃ → 2GaBO₃ [Gallium metaborate, interfacial bonded phase, 1100 °C] Simultaneously, the Al2O3 component in the whiskers undergoes a solid-phase diffusion reaction with the Ga2O3 matrix, forming a corundum-like solid solution: Al₂O₃ + Ga₂O₃ → 2(Ga,Al)O₃ [Corundum-like solid solution, interfacial bonding layer, 1100 °C] Silicon carbide (SiC) fibers are inert reinforcing phases. In an air atmosphere at 1100 °C, a slight, controllable oxidation occurs on the fiber surface, forming a SiO2 passivation film. Subsequently, SiO2 undergoes a trace solid-phase reaction with Ga2O3. SiO2 + Ga2O3 → Ga2SiO5 [Gallium silicate, trace amounts at the interface, 1100 °C] The three types of interfacial bonded phases (GaBO3, (Ga,Al)O3, and Ga2SiO5) together form a continuous chemically bonded interfacial bonding layer with a thickness of about 5-15 nm at the interface between each reinforcing phase and the Ga2O3 matrix. The synergistic reinforcement of aluminum borate whiskers (elastic modulus of about 260 GPa) and SiC fibers (elastic modulus of about 480 GPa) significantly improves the overall compressive strength and toughness of the foam ceramic, completely avoiding the risk of reinforcing phase detachment under service conditions.

[0059] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytic active component, tungsten trioxide (WO3), undergoes an interfacial reaction with Ga2O3 via solid-phase diffusion during sintering at 1100 °C. +Diffusion towards the WO3 particle interface leads to the in-situ formation of a novel photocatalytically active phase of gallium-tungsten composite oxide: Ga₂O₃ + 3WO₃ → Ga₂(WO₄)₃ [Gallium tungstate, orthorhombic crystal system, 1100 °C] Ga2(WO4)3 (orthorhombic crystal system) E g ≈ 3.0-3.5 eV, near-edge response in visible light) preferentially accumulates at the neck interface of WO3 particles in the form of a nanoscale interfacial film, not only strengthening intergranular chemical bonding, but more importantly providing an additional UV-Vis responsive active phase. Residual WO3 phase ( E g ≈ 2.6-2.8 eV, l (<460 nm, visible light response) Maintains the original structure and participates in the construction of functional phase network. The conduction band position of WO3 is approximately +0.3 eV (vs NHE), and the valence band position is approximately +3.1 eV (vs NHE).

[0060] (5) Heterogeneous structure construction and tetracycline-targeted degradation mechanism The Ga2(WO4)3 generated in situ during the controlled sintering heat treatment process, together with the residual Ga2O3 phase and WO3 phase, jointly construct a Ga2O3 / WO3 / Ga2(WO4)3 step-scheme heterojunction system. (1) Ga2O3 (reduced photocatalyst component): Conduction band position is approximately -0.7 eV (vs NHE), valence band position is approximately +4.1 eV (vs NHE), and band gap is approximately 4.8 eV (deep ultraviolet response). Its conduction band electrons have reducing properties ( E CB < -0.33 eV), which can drive the single-electron reduction of O2 to produce O2. - Superoxide radicals; (2) WO3 (oxidized photocatalyst component): Conduction band position is approximately +0.3 eV (vs NHE), valence band position is approximately +3.1 eV (vs NHE), and band gap is approximately 2.6-2.8 eV (vs NHE). l <460 nm, visible light response). Its valence band holes have strong oxidizing properties (overpotential reaches 0.72 eV relative ·OH generation potential), efficiently oxidizing water molecules / OH. - High concentrations of ·OH are generated; (3) Ga2(WO4)3 (band bridging intermediate phase): The conduction band position is approximately +0.1 eV (vs NHE), and the valence band position is approximately +3.3 eV (vs NHE), serving as a band gradient bridging phase between Ga2O3 and WO3. In the S-type heterojunction mechanism, the built-in electric field drives the weakly reducing electrons (+0.3 eV) of the WO3 conduction band and the strong oxidizing holes (+4.1 eV) of the Ga2O3 valence band to recombine and annihilate in a directional manner at the Ga2(WO4)3 interface, while retaining the strong reducing conduction band electrons (-0.7 eV) of Ga2O3 to efficiently generate ·O2. - Furthermore, the strong oxidizing properties of WO3 lead to the efficient generation of ·OH from valence band holes (+3.1 eV), achieving a synergistic and efficient supply of dual active species.

[0061] The above system targets the pollutant tetracycline (TC, C). 22 H 24 N2O8, M W Targeted degradation (444.45 g / mol) based on the multifunctional group bond energy distribution characteristics of TC molecules and the above-mentioned ·OH-dominated / ·O2 - Precise matching of the synergistic system. The TC molecule consists of four fused rings (AD rings). The bond energies and breaking difficulties of each key chemical bond are as follows: the CN bond energy of the N,N-dimethylamino (-N(CH3)2) at C4 position is about 305-315 kJ / mol, which is the lowest bond energy site in the whole molecule. The electrophilic ·OH is the easiest to attack and is the core attack target for targeted initiation; the phenolic hydroxyl C-OH (about 360 kJ / mol) and enol C-OH (about 360 kJ / mol) at C12a position are next; the aromatic C=C conjugated bond of the benzene ring D ring (about 510 kJ / mol) and the carbonyl C=O bond at C1 and C11 positions (about 745 kJ / mol) have the highest bond energies, requiring multi-step synergy of active species to achieve ring-opening mineralization. Accordingly, the targeted degradation of tetracycline by the Ga2O3 / WO3 / Ga2(WO4)3S-type heterojunction system proceeds in three steps: (1) Targeted initiation (C4-N,N-dimethylamino demethylation and side chain degradation): Due to its high electrophilicity, ·OH preferentially attacks the N,N-dimethylamino CN bond at the C4 position of the TC molecule (305-315 kJ / mol), initiating the gradual oxidative degradation of N-demethylation and amino side chain, generating demethyltetracycline and a series of deamination derivatives, accompanied by the release of formaldehyde (HCHO); at this stage, ·OH also simultaneously attacks the D ring of the benzene ring where the phenolic hydroxyl group is located at the C12a position (360 kJ / mol), triggering benzene ring hydroxylation, introducing an additional -OH functional group, greatly weakening the conjugation stability of the D ring, and providing a low-barrier channel for the subsequent ring opening of the D ring; (2) Oxidative destruction of chromophores (cooperative attack by C1, C11 carbonyl groups and C=C conjugated system): Ga2O3 conduction band strong reducing electrons (-0.7 eV) drive the single-electron reduction of O2 to produce a large amount of ·O2. - Superoxide radicals; O2 - Nucleophilic addition occurs with the enol-type C=CC=O conjugated chromophore system in the TC molecule, and the ·OH group synergistically attacks the carbonyl C=O at the C1 and C11 positions, gradually destroying the π-conjugated light absorption system of the TC molecule. This causes the characteristic absorption peak of the solution absorbance near 420 nm to decrease rapidly, the chromophore structure to disintegrate, and the TC molecule to be transformed into a low-toxicity non-chromophore intermediate. (3) Ring opening and complete mineralization of polycyclic structures: After pretreatment in steps (1) and (2), the conjugation stability of the TC tetracyclic structure is significantly weakened; high concentrations of ·OH and ·O2 - The synergistic and continuous attack on the remaining AC fused ring C=C aromatic conjugated system (approximately 510 kJ / mol) overcomes the cyclization stabilization energy, sequentially driving the ring-opening of each fused ring. Through the gradual oxidation and mineralization of short-chain organic acid intermediates such as oxalic acid, acetic acid, and formic acid, TC is ultimately completely mineralized into CO2, H2O, and NH4. + NO3 - and SO4² - Inorganic small molecules, etc., to achieve complete harmlessness of tetracycline.

[0062] The specificity of the targeted matching stems from the precise adaptation between the distribution of active species in the system and the bond energy gradient of the TC molecule: the high electrophilicity of ·OH is highly matched with the lowest bond energy (305-315 kJ / mol) of the N,N-dimethylamino CN bond at the C4 position of the TC molecule, enabling preferential initiation and N-demethylation; the high concentration of ·OH generated by the strong oxidizing valence band hole (+3.1 eV) of WO3 significantly drives the direct oxidation of the C12a phenolic hydroxyl benzene ring; and the ·O2 generated by the strong reducing conduction band electron (-0.7 eV) of Ga2O3... - The nucleophilic addition is precisely matched with the TC enol-type chromophore conjugated system; the S-type heterojunction mechanism simultaneously retains the strong reducing conduction band electrons of Ga2O3 (-0.7 eV) and the strong oxidizing valence band holes of WO3 (+3.1 eV), achieving synergistic targeted attack and complete mineralization of tetracycline multifunctional groups under the synergistic drive of deep ultraviolet-visible light.

[0063] The monolithic gallium oxide-based photocatalytic foam ceramic has a cylindrical macroscopic shape; compressive strength ≥ 0.5 MPa, porosity ≥ 84%, pore structure connectivity ≥ 82%, and a tetracycline (TC) degradation rate ≥ 93% under ultraviolet-visible light. Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of gallium oxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0064] Example 4 A method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement includes the following steps: S1: Add organic additives and pH adjusters to deionized water and disperse them evenly to form a homogeneous solution; add gallium oxide powder, photocatalytic active components, sintering aids and defect control agents to the solution in batches and disperse them evenly to form a gallium oxide-based suspension slurry; add fiber and / or whisker reinforcing phase to the suspension slurry and disperse it evenly to form a gallium oxide-based composite slurry.

[0065] S2: The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and excess slurry on the surface is removed by squeezing or centrifugation; then drying is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank.

[0066] S3: The gallium oxide-based foam ceramic wet blank obtained in step S2 is first naturally air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried wet blank is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic blank with a three-dimensional interconnected pore structure.

[0067] S4: The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous and dense ceramic skeleton network through particle fusion and phase boundary bonding, effectively reducing the sintering temperature and ensuring the structural integrity of the three-dimensional interconnected channels. At the same time, defect control agents suppress Ga³⁺ during high-temperature sintering through solid solution substitution and grain boundary segregation mechanisms. + Excessive reduction and Ga2O volatilization loss, excessive oxygen vacancy generation, lattice distortion, and abnormal growth of Ga2O3 grains are controlled to keep the grain size within a small range, maintaining a high specific surface area and porosity of the material. At the same time, the defect structure and photoelectronic properties of the material are precisely regulated. The photocatalytic active component constructs a photocatalytic functional heterojunction system with the gallium oxide matrix through in-situ solid-phase reaction, which enhances the separation efficiency of photogenerated carriers and achieves efficient targeted degradation of target pollutants.

[0068] In step S1, the gallium oxide powder is a β-Ga2O3 phase powder with a purity > 98 wt.% and an average particle size D50 of 1.5 μm; The photocatalytic active component is titanium dioxide (TiO2) with a purity >98 wt.%, an average particle size D50 of 0.6 μm, and an addition amount of 60 wt.% of the Ga2O3 powder mass. The sintering aid is strontium carbonate (SrCO3) with a purity >98 wt.%, an average particle size D50 of 5 μm, and an addition amount of 10 wt.% of the Ga2O3 powder mass. The defect control agent is lanthanum trioxide (La₂O₃) with a purity >98 wt.%, an average particle size D50 of 2 μm, and an addition amount of 10 wt.% of the Ga₂O₃ powder mass. The organic additives include binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; wherein the binder is starch (ST); the plasticizer is triethyl acetylacetic acid (ATEC); the dispersant is polyaspartic acid (PASP); the surfactant is polysorbate 80 (Tween-80); the rheology modifier is guar gum (GG); and the defoamer is polyether-modified siloxane (BYK-024). The pH adjuster is ammonia water (NH3·H2O, 2 mol / L); The reinforcing phase is magnesium borate whiskers with an average length of 17 μm and an average diameter of 0.8 μm. The gallium oxide-based composite slurry has a solid content of 52 vol.% and a pH of 10. The amounts of each component of the organic additive and the reinforcing phase added are based on the total mass of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents, and are as follows: binder, 1.2 wt.%; dispersant, 2.7 wt.%; plasticizer, 0.8 wt.%; surfactant, 3.9 wt.%; rheology modifier, 1.7 wt.%; defoamer, 2.3 wt.%; reinforcing phase, 24 wt.%. In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the gallium oxide-based suspension slurry and the composite slurry are also uniformly dispersed by mechanical stirring. For the uniform dispersion of the homogeneous solution, the mechanical stirring rate was 1400 rpm; the stirring time was 9 min; the stirring paddle material was polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. The stirring rate for both the gallium oxide-based suspension slurry and the composite slurry was 2500 rpm; the stirring time was 30 min; the stirring paddle was made of polytetrafluoroethylene; and the distance between the stirring paddle blade and the bottom of the slurry container was 0.5 cm. In step S2, the organic foam is made of polyurethane (PU), has a pore density of 10 PPI, and has a macroscopic shape of cuboid. The impregnation is carried out under normal pressure; the impregnation process is carried out at 20°C for 100 seconds. The pressure of the extrusion desizing is controlled within 1 MPa, and the thickness of the organic foam after extrusion is compressed to 90% of the original thickness; The drying process employs a programmed temperature increase method, with a drying temperature of 70℃, and continues until the mass change rate is <1% / h. After five cycles of impregnation-desizing-drying-impregnation, the cumulative loading of the composite slurry reaches 480% of the original mass of the organic foam. In step S3, the natural air drying is carried out in a ventilated environment at a temperature of 35°C, a relative humidity of 20%, a ventilation rate of 1 m / s, and a natural air drying time of 11 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 75°C at a rate of 10°C / min, and the temperature is maintained for 5 hours. The airflow rate inside the oven is 1 m / s, and the drying endpoint is a mass change rate of <0.05% / h. The degumming heat treatment includes: In the first stage, the temperature is increased to 250℃ at a rate of 10℃ / min and held for 20 min. In the second stage, the temperature is increased to 450℃ at a rate of 2℃ / min and held for 2 min. The third stage involves raising the temperature to 600℃ at a rate of 4℃ / min and holding it for 10 minutes. The degumming heat treatment process is carried out under a selected atmosphere, namely air, with a gas flow rate of 1000 mL / min and the furnace pressure maintained at gauge pressure +800 Pa. In step S4, the process conditions for the controlled sintering heat treatment include: sintering temperature 1500℃, constant temperature time 1min, and heating rate 10℃ / min. During the controlled sintering heat treatment, the components undergo the following chemical reactions in sequence, ultimately constructing a cascaded heterojunction system with targeted degradation function: (1) Thermal decomposition of sintering aids and liquid-phase assisted sintering reaction The sintering aid strontium carbonate (SrCO3) is an alkaline earth metal carbonate type precursor sintering aid with a decomposition temperature of approximately 1100 °C. In this embodiment, when the temperature is raised to approximately 1100 °C, SrCO3 undergoes complete thermal decomposition, generating highly active SrO and CO2 gas. SrCO3→ SrO + CO2↑ [In-situ thermal decomposition, ≈1100 °C] The generated SrO reacts rapidly with the surrounding Ga2O3 particles at the interface to form a strontium-gallium composite oxide sintering-assisted activation phase. SrO + Ga2O3 → SrGa2O4 [orthorhombic strontium gallium salt, grain boundary activated phase, ≈1200 °C] The SrGa2O4 phase (orthorhombic system) forms a eutectic liquid phase (eutectic point approximately 1420 °C) in the Ga2O3-SrO binary system. During the heating process to 1500 °C, a transient Sr-Ga liquid phase is formed at the particle interface. Through capillary force, Ga2O3 and TiO2 particles rearrange, and the width of the neck connection region between particles is precisely controlled within 10 μm, effectively promoting the densification of the continuous skeleton rib network of foam ceramics. At the same time, the SrGa2O4 grain boundary phase inhibits the abnormal growth of Ga2O3 grains through the grain boundary pinning mechanism, maintaining a high specific surface area of ​​the skeleton.

[0069] (2) Grain boundary segregation suppression and stabilization reaction of defect control agents The defect control agent, lanthanum trioxide (La₂O₃), belongs to the grain boundary segregation inhibitor category. La³ + The ionic radius is 0.116 nm, which is much larger than that of Ga³⁺. + (0.062 nm, tetrahedral) and Ga³ + (0.076 nm, octahedral position), does not satisfy the solid solution rule, and has extremely low solid solubility in the Ga₂O₃ lattice. La³ + It mainly accumulates in the grain boundary region of Ga2O3 and TiO2 grains through grain boundary segregation mechanism, and undergoes a solid-state interfacial reaction with Ga2O3 at a high temperature of 1500 °C to form a lanthanum gallium composite oxide grain boundary pinning phase. La₂O₃ + Ga₂O₃ → 2LaGaO₃ [Perovskite-type lanthanum gallate, grain boundary pinned phase, 1500 °C] The generated LaGaO3 phase (perovskite structure, orthogonal distortion) E (g ≈ 5.6 eV) is continuously distributed in the form of a nanofilm at the grain boundaries of Ga2O3, and the abnormal growth of Ga2O3 and TiO2 grains is simultaneously suppressed through the solute drag effect, thereby reducing the average grain size of the two phases. D 50 The thickness of the Ga₂O vapor is controlled within 3 μm; simultaneously, the LaGaO₃ perovskite film enriched at the grain boundaries effectively blocks the grain boundary diffusion channels of Ga₂O vapor, thus kinetically inhibiting the diffusion of Ga₃. + Excessive reduction loss at 1500 °C maintains a high retention ratio and structural stability of the Ga2O3 photocatalytic active phase.

[0070] (3) Enhanced in-situ interfacial reaction between the phase and the matrix The magnesium borate (Mg2B2O5) whiskers, which are the reinforcing phase, are active reinforcing phases. Their interfacial bonding mechanism during high-temperature sintering at 1500 °C is as follows: the surface B2O3 component (melting point approximately 450 °C) in the Mg2B2O5 whiskers (rod-shaped magnesium pentaborate) diffuses into the Ga2O3 matrix interface in liquid phase form, undergoing an in-situ liquid-solid interfacial reaction with Ga2O3 to generate a gallium borate chemical bond layer. B₂O₃(l) + Ga₂O₃ → 2GaBO₃ [Gallium metaborate, interfacial bonded phase, 1500 °C] Simultaneously, the MgO component on the whisker surface migrates outward through solid-phase diffusion and reacts in situ with the Ga2O3 matrix to form a spinel-type interfacial bonding layer: MgO + Ga2O3 → MgGa2O4 [Spinel magnesium gallate, interfacial bonding layer, 1500 °C] The generated GaBO3 and MgGa2O4 together form a continuous chemically bonded interface layer with a thickness of about 5-15 nm at the interface between Mg2B2O5 whiskers and Ga2O3 matrix, upgrading the bonding mode between whiskers and matrix from physical interlocking to chemical bonding, significantly improving the interfacial shear strength; Mg2B2O5 whiskers (elastic modulus of about 270 GPa) provide uniformly distributed load transfer paths for the foam ceramic skeleton ribs, and together with the interlocking network formed by them in the three-dimensional skeleton, significantly improve the overall compressive strength and toughness of the foam ceramic.

[0071] (4) In-situ formation reaction of photocatalytically active new phase The photocatalytic active component, titanium dioxide (TiO2), undergoes an interfacial reaction with Ga2O3 via solid-phase diffusion during sintering at 1500 °C. 4+ Diffusion towards the interface of Ga2O3 particles, Ga³ + Reverse diffusion towards the TiO2 particle interface leads to the in-situ generation of a new photocatalytically active phase of gallium-titanium composite oxide at the interface between the two phases. Ga₂O₃ + TiO₂ → Ga₂TiO₅ [orthorhombic gallium titanate, 1500 °C] Ga2TiO5 (orthorhombic crystal system, space group P) name The band gap is approximately 3.5-3.8 eV. l <325-355 nm, UV response), conduction band position approximately -0.5 eV (vs NHE), valence band position approximately +3.2 eV (vs NHE), exhibiting excellent photochemical stability. The formation of the Ga2TiO5 phase transforms TiO2 into Ti... 4+The TiO2 photocatalytic active components are fixed at the interface in the form of titanate and the stoichiometry of the TiO2 photocatalytic active components is effectively maintained under high temperature sintering conditions of 1500 °C. Due to the extremely short sintering time (1 min) in this embodiment, the new Ga2TiO5 phase is mainly enriched in the form of nano-scale thin film at the interface between Ga2O3 and TiO2 particles. A large amount of unreacted Ga2O3 phase and TiO2 phase maintain the original crystal phase structure and jointly participate in the construction of the photocatalytic functional phase network.

[0072] (5) Heterogeneous structure construction and bisphenol A targeted degradation mechanism The Ga2TiO5 generated in situ during the controlled sintering heat treatment process, together with the residual Ga2O3 phase, TiO2 phase, and LaGaO3 phase at the grain boundaries, jointly construct a Ga2O3 / TiO2 / Ga2TiO5 S-type heterojunction system. (1) Ga2O3 (OP, oxidation-type photocatalyst): Conduction band position is approximately -0.7 eV (vs NHE), valence band position is approximately +4.1 eV (vs NHE), and band gap is approximately 4.8 eV (deep ultraviolet response). Its valence band holes have super strong oxidizing properties (overpotential reaches +1.72 eV relative ·OH generation potential), efficiently oxidizing water molecules / OH - It produces a high concentration of ·OH; because its conduction band potential is relatively positive and its reducing ability is relatively weak, photogenerated electrons are easily recombinated. (2) TiO2 (RP, reduced photocatalyst): conduction band position is approximately -0.29 eV (vs NHE), valence band position is approximately +2.91 eV (vs NHE), and band gap is approximately 3.2 eV ( l <390 nm, UV response). Its conduction band electrons have reducing properties ( E CB < -0.33 eV, thermodynamic edge (requires synergistic effect), is retained in the S-type heterojunction to drive O2 reduction and generate ·O2. - Superoxide radicals; due to their shallow valence band potential and insufficient oxidizing ability, photogenerated holes are easily recombinated. (3) Ga2TiO5 (band-bridging intermediate phase): The conduction band position is approximately -0.5 eV (vs NHE), and the valence band position is approximately +3.2 eV (vs NHE), serving as a band gradient bridging phase between Ga2O3 and TiO2. In the S-type heterojunction mechanism, the built-in electric field drives the weakly oxidizing holes (+2.91 eV) in the TiO2 valence band and the weakly reducing electrons (-0.7 eV) in the Ga2O3 conduction band to recombine and annihilate in a directional manner at the Ga2TiO5 bridging interface. At the same time, the highly oxidizing valence band holes (+4.1 eV) of Ga2O3 are retained to efficiently generate ·OH, and the conduction band electrons (-0.29 eV) of TiO2 are used to synergistically generate ·O2. -This enables the synergistic and efficient supply of dual active species.

[0073] The above system is effective against the target pollutant bisphenol A (BPA, C). 15 H 16 O2, M W = 228.29 g / mol, i.e., 4,4'-isopropylidene bisphenol), targeted degradation based on the bond energy characteristics of BPA molecules and the above-mentioned ·OH-dominant / ·O2 - Precise matching of the synergistic system. The BPA molecule is composed of two p-hydroxyphenol groups connected by an isopropylidene (-C(CH3)2-) carbon bridge. The bond energies and breaking priorities of the key chemical bonds are as follows: the isopropylidene carbon bridge C-OH bond has a bond energy of approximately 346 kJ / mol, which is the lowest bond energy site in the entire molecule and the core attack target initiated by ·OH; the phenol C-OH bond (approximately 360 kJ / mol) is next; the aromatic C=C conjugated bond of the benzene ring (approximately 510 kJ / mol) has the highest bond energy and requires multi-step synergistic ring-opening mineralization by active species. Accordingly, the system performs targeted degradation of bisphenol A in three steps: (1) Targeted initiation (breaking of isopropylidene carbon bridge CC bond, dissociation of two phenolic rings): Ga2O3’s strong oxidizing properties and valence band hole (+4.1 eV) directly oxidize the phenolic hydroxyl group (-OH) of BPA molecule, inducing single-electron oxidation to form phenoxy radical (PhO•); high concentration of ·OH preferentially attacks the isopropylidene carbon bridge CC bond (346 kJ / mol), inducing homolytic cleavage of CC, breaking the BPA double benzene ring structure into two independent p-hydroxybenzyl alcohol / benzoquinone intermediates and acetone small molecules (CH3COCH3), completing the dissociation of the BPA core structure; (2) Phenolic ring hydroxylation activation (phenol introduces an additional -OH, forming a catechol / hydroquinone intermediate): ·OH attacks the high electron cloud density carbons at C2 and C4 positions of the phenol ring, introducing an additional -OH through electrophilic addition and hydroxide reaction, successively converting phenol into catechol (catechol) and hydroquinone (hydroquinone); TiO2 conduction band electrons drive O2 to generate ·O2 - Nucleophilic addition with benzoquinone intermediates accelerates the destruction of the π-conjugated system of the benzene ring, providing a low-barrier channel for subsequent ring opening of the benzene ring; (3) Ring opening and complete mineralization of benzene ring: ·OH and ·O2 - The synergistic attack on the catechol / hydroquinone benzene ring C=C aromatic conjugated system (approximately 510 kJ / mol) drives the sequential opening of the benzene ring. Through the gradual oxidation and mineralization of short-chain organic acid intermediates such as maleic acid, oxalic acid, acetic acid, and formic acid, BPA is finally completely mineralized into inorganic small molecules such as CO2 and H2O, achieving efficient degradation of bisphenol A from the dissociation of the core structure to complete mineralization.

[0074] The specificity of the targeted matching stems from the precise adaptation between the distribution of active species in the system and the bond energy gradient of BPA: the strong oxidizing holes (+4.1 eV) of Ga2O3 and ·OH synergistically initiate the targeted breaking of the C-bond (346 kJ / mol) of the isopropylidene carbon bridge in BPA, achieving preferential breakage of the core structure; the S-type heterojunction mechanism facilitates the interaction of ·OH and ·O2. - The simultaneous retention of dual active species ensures continuous and efficient attack on the high bond energy benzene ring system (510 kJ / mol); the LaGaO3 grain boundary pinning phase maintains the clarity of the Ga2O3 / TiO2 interface and the built-in electric field strength, ensuring the efficient degradation of bisphenol A from targeted initiation to complete mineralization under deep ultraviolet-ultraviolet light irradiation.

[0075] The monolithic gallium oxide-based photocatalytic foam ceramic has a cuboid macroscopic shape; compressive strength ≥ 0.8 MPa, porosity ≥ 87%, pore structure connectivity ≥ 80%, and bisphenol A (BPA) degradation rate ≥ 96% under ultraviolet light; Those skilled in the art can determine the process window that satisfies the above effects through limited experiments under conventional equipment conditions, based on the specific type of gallium oxide powder, the type of photocatalytic active component, and the characteristics of the reinforcing phase.

[0076] The above description is merely a preferred embodiment of this application and is not intended to limit this application in any form or substance. It should be noted that those skilled in the art can make several improvements and additions without departing from this application, and these improvements and additions should also be considered within the scope of protection of this application.

Claims

1. A method for preparing gallium oxide-based photocatalytic foam ceramics with multi-mechanism synergistic enhancement, characterized in that, Includes the following steps: Step S1: Preparation of gallium oxide-based composite paste Organic additives and pH adjusters are added to deionized water and dispersed evenly to form a homogeneous solution; gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents are added to the homogeneous solution in batches and dispersed evenly to form a gallium oxide-based suspension slurry; fiber and / or whisker reinforcing phases are added to the suspension slurry and dispersed evenly to form a gallium oxide-based composite slurry; Step S2: Preparation of gallium oxide-based foam ceramic wet blank The organic foam is completely immersed in the gallium oxide-based composite slurry obtained in step S1 for impregnation treatment; after impregnation, the organic foam is removed and the excess slurry on the surface is removed by squeezing or centrifugation; then drying treatment is performed; the above impregnation-deslurry-drying cycle is repeated several times to allow the gallium oxide-based composite slurry to accumulate layer by layer on the surface of the organic foam skeleton to obtain a gallium oxide-based foam ceramic wet blank. Step S3: Prepare gallium oxide-based foam ceramic preform The gallium oxide-based foam ceramic green body obtained in step S2 is first air-dried to remove surface free moisture; then it is dried by programmed temperature rise to further remove internal moisture; then the dried green body is subjected to debinding heat treatment by gradient temperature rise to fully remove organic foam and organic additives by thermal debonding, while gallium oxide particles, photocatalytic active components, sintering aids, defect control agents and reinforcing phases are initially sintered together to form gallium oxide-based foam ceramic green body with a three-dimensional interconnected pore structure. Step S4: Sintering and Heterogeneous Structure Construction The green blank obtained in step S3 is subjected to controlled sintering heat treatment. Under the action of sintering aids, gallium oxide and photocatalytic active components form a continuous ceramic skeleton network through particle fusion and phase boundary bonding, thereby reducing the sintering temperature and maintaining the three-dimensional channel structure. At the same time, defect control agents suppress Ga³⁺ segregation through solid solution substitution and grain boundary segregation. + Excessive reduction and Ga2O volatilization control oxygen vacancy generation and grain size maintain high specific surface area and porosity, and regulate defect structure and photoelectronic properties; the photocatalytic active component constructs a photocatalytic functional heterojunction system with gallium oxide matrix through in-situ solid-phase reaction, improves the separation efficiency of photogenerated carriers, and achieves efficient degradation of target pollutants.

2. The preparation method according to claim 1, characterized in that, In step S1, the average particle size of the Ga2O3 powder is 10 nm-80 μm, and it is selected from any one or a combination of α-Ga2O3 phase powder, β-Ga2O3 phase powder, γ-Ga2O3 phase powder, mixed crystalline phase Ga2O3 powder or modified powder thereof. The modified powder is obtained by modifying the Ga2O3 powder through any of the following modification methods: 1) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³ + Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4+ Pr³ + Pr 4 + 、Nd³ + Sm³ + Eu³ + Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ + Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4 + Ir 4+ Pt² + W 6+ Pt 4+ and Au³ + Any one or more of the following, with a doping concentration of 0.1-15 at% 2) Anion doping, wherein the anion is selected from any one or more of B, C, N, F, P, S, Cl, Br and I, and the doping concentration is 0.5-10 at% 3) Oxygen vacancy regulation, oxygen vacancy concentration is 10 18 -10 21 cm -3 ; 4) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The modified powder still possesses semiconductor properties, with a band gap ranging from 1.5 to 5.5 eV; The photocatalytic active component is an inorganic oxide powder with semiconductor properties, and its band gap ranges from 1.5 to 5.5 eV; it is selected from at least one component from the following I) - V); I) Single metal oxides The general chemical formula is M m O n M is a single metallic element, m = 1-3, n = 1-5; including one or more of TiO2, ZnO, WO3, Bi2O3, Fe2O3, Cu2O, V2O5, MoO3, SnO2, MnO2, ZrO2, Nb2O5, Ta2O5, In2O3, GeO2, RuO2, IrO2, Co3O4, NiO, Mn3O4, CuO, Ag2O, CoO, MnO, SnO, Sb2O3, Fe3O4, and Au2O and their modified derivatives; II) Composite metal oxides Composed of two or more metal cations, and further subdivided according to crystal structure as: a) Perovskites and their derived phases: general formula ABO3 or A (n+1) B n O (3n+1) , where n is an integer from 1 to 3, A is selected from at least one of La, Bi, Ba, Sr, Ca, Pb, Na and K, and B is selected from at least one of Ti, Zr, Hf, Nb, Ta, W, Mo, V, Cr, Mn, Fe, Co, Ni, Al, Ga and Sn; b) Spinel-type oxides: with the general formula AB₂O₄, wherein A is selected from at least one of Mg, Zn, Ni, Co, Cu, Fe, Mn and Li, and B is selected from at least one of Al, Ga, Cr, Fe, Mn, Co and Ti; c) Layered oxyacid salts having a layered crystal structure with an interlayer spacing of 0.5 nm to 1.5 nm, selected from at least one of the following: c1) Layered titanates, with the general formula A2Ti3O7 or ATi2O5, wherein A is selected from H, Li, Na, K, Rb or Cs; c2) Protonated layered niobates or tantalates, with the general formula HNb3O8 or HTa2O6; c3) Aurivillius phase bismuth-based oxides, selected from Bi₂WO₆, Bi₂MoO₆, and Bi₄Ti₃O₆. 12 At least one of them; c4) Layered nickelates, with the general formula ANiO2, wherein A is selected from Li or Na; d) Other functional oxoacid salts, selected from at least one of the following groups: d1) Scheelite-type oxides, with the general formula AWO4, AMoO4 or AVO4, wherein A is selected from Bi, Ca, Sr, Zn or Pb; d2) Perovskite-type rare earth ferrates, with the general formula LnFeO3, wherein Ln is selected from La, Pr, Nd or Sm; d3) Pyrochlore-type oxides, with the general formula Ln2B2O7, wherein Ln is selected from La, Gd, Sm or Nd, and B is selected from Ti, Zr or Sn; d4) Tungsten bronze type oxide, with the general formula M x TO3, where T is selected from W, Nb, or Ta, M is selected from Na or K, and 0.1 ≤ x ≤ 1.0; d5) Olivine-type oxides, with the general formula M2SiO4 or M2GeO4, wherein M is selected from Mg, Zn, Fe or Mn; d6) Inverse spinel-type stannate Zn2SnO4; d7) Copper-iron ore type oxides, with the general formula CuMO2, wherein M is selected from Fe, Al, Ga or Cr; III) Rare earth-based oxides a) Single rare earth oxide Ln a O x , where Ln is La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc, a = 1–2, x = 1.5–3; b) Rare earth composite oxides: including perovskite-type LaMO3, NdMO3, ScMO3, YMO3, PrMO3, SmMO3, EuMO3, GdMO3, TbMO3, DyMO3, HoMO3, ErMO3, TmMO3, YbMO3, and LuMO3, where M is selected from transition metals Fe, Co, Sc, Ti, V, Cr, Mn, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, and W. Re, Os, Ir, Pt, Au, or Hg; pyrochlore-type Gd₂Ti₂O₇, Y₂Zr₂O₇, Sc₂Ti₂O₇, La₂Ti₂O₇, Ce₂Ti₂O₇, Pr₂Ti₂O₇, Nd₂Ti₂O₇, Sm₂Ti₂O₇, Eu₂Ti₂O₇, Tb₂Ti₂O₇, Dy₂Ti₂O₇, Ho₂Ti₂O₇, Er₂Ti₂O₇, Tm₂Ti₂O₇, Yb₂Ti₂O₇, Lu₂Ti₂O₇; bismuth rare earth co-doped oxides Bi. 1-x Ln x VO4, wherein Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Sc, Y, x = 0.1-0.5, and at least one of the layered rare earth oxides La2O2CO3, Pr4O7, Ce2O2CO3, Nd2O2CO3, Sm2O2CO3, Eu2O2CO3, Gd2O2CO3, Tb2O2CO3, Dy2O2CO3, Ho2O2CO3, Er2O2CO3, Tm2O2CO3, Yb2O2CO3, Lu2O2CO3, Sc2O2CO3, Y2O2CO3; the interlayer spacing of the layered rare earth oxide structure is 0.8-1.2 nm; IV) Frontier structural metal oxides a) High-entropy oxides: general formula is (M1, M2, ... M n ) a O M1, M2, ..., Mn are at least five different metallic elements, each independently selected from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Mg, Al, Li, Zr, Nb, Mo, Sn, Hf, Ta, W, or Ce, with each metallic element accounting for 5% to 35% of the total metallic elements, and the configuration entropy ΔS of the high-entropy oxide is... mix ≥ 1.5R, where R is the ideal gas constant 8.314 J·mol - ¹·K - ¹; (b) A two-dimensional nano-metal oxide, wherein the matrix material of the two-dimensional nano-metal oxide is selected from at least one of TiO2, MnO2, MoO3, V2O5, Co3O4, Fe2O3, SnO2, ZnO, WO3 and Nb2O5, has a plate-like or layered morphology, has a thickness of 0.5 nm to 10 nm, has a lateral dimension to thickness ratio ≥ 50, and the two-dimensional nano-metal oxide has preferentially exposed crystal planes, wherein the crystal planes are selected from at least one of the {001}, {010}, {100} and {110} plane families; c) MOF-derived porous oxides, wherein the MOF-derived porous oxides are obtained by heat treatment conversion of metal-organic framework precursors, wherein the metal center of the precursor is selected from at least one of Zn, Co, Fe, Cu, Zr, Ti, Ni and Al, and the resulting oxides retain the morphological characteristics and pore structure of the precursors, with a specific surface area ≥ 50 m² / g, pore volume ≥ 0.1 cm³ / g, and pore size distribution spanning from micropores to mesopores, ranging from 0.5 nm to 50 nm; V) Precursor compound: is the water-insoluble oxalate and / or carbonate corresponding to the metal oxides in I)-II), wherein the precursor compound decomposes in situ during sintering heat treatment to generate the corresponding photocatalytically active oxide; The term "insoluble in water" means that the solubility in deionized water at 25°C is ≤0.1 g / 100 mL. VI) The photocatalytic active component described in any of I) to IV) above is modified using one or more of the following methods, and the resulting powder satisfies a band gap of 1.5-5.5 eV: a) Cation doping, wherein the cation is selected from Li + Na + K + 、Rb + Cs + Mg² + Ca² + Sr² + Ba² + Al³ + Ga³ + In³ + Sn 4+ Sb³ + Sb 5+ Bi³ + ,Sc³ + Ti 4+ V³ + V 4+ V 5+ Cr³ + Cr 4+ Mn² + Mn³ + Mn 4+ Fe² + Fe³ + Co² + Co³ + Ni² + Ni³ + Cu² + Zn² + Y³ + Zr 4+ 、Nb 5+ Mo 6+ Ru 4+ 、Rh³ + Pd² + Ag + La³ + Ce³ + Ce 4+ Pr³ + Pr 4+ 、Nd³ + Sm³ + Eu³ + Gd³ + Tb³ + 、Tb 4+ Dy³ + Ho³ + Er³ + Tm³ + Yb³ + Lu³ + Hf 4+ Ta 5+ Re 4+ Re 6+ Os 4+ Ir 4+ Pt² + Pt 4+ W 6+ and Au³ + At least one of them, with a doping ratio of 0.1-15 at%; b) Anion doping, wherein the anion is selected from one or more of B, C, N, F, P, S, Cl, Br and I, and the doping ratio is 0.5-10 at% c) Oxygen vacancy regulation, with an oxygen vacancy concentration of 10. 18 -10 21 cm -3 ; d) Defect engineering modification, dislocation / grain boundary density 10 14 -10 16 cm -2 ; The amount of photocatalytic active component added is 5-80 wt.% of the gallium oxide powder mass; the amount of precursor compound added is based on the theoretical mass of the corresponding photocatalytic active oxide generated by its complete thermal decomposition, i.e., oxide equivalent.

3. The preparation method according to claim 1, characterized in that, The sintering aid is selected from at least one of the following components: a) Low-melting-point oxides: bismuth trioxide, vanadium pentoxide, boron trioxide, molybdenum trioxide, tellurium dioxide; b) Eutectic / Active Oxides: Zinc oxide, copper oxide, ferric oxide, nickel oxide, cobalt oxide, cobalt tetroxide, manganese dioxide, manganese trioxide, chromium trioxide, indium trioxide, antimony trioxide, tin dioxide; c) Network forming agents: silicon dioxide, phosphorus pentoxide, germanium dioxide, tellurium dioxide, boron trioxide; d) Alkali metal and alkaline earth metal oxides: magnesium oxide, lithium carbonate, calcium carbonate, strontium carbonate, barium carbonate; e) Rare earth oxide sintering aids: lanthanum oxide, yttrium oxide, scandium oxide, neodymium oxide, samarium oxide, gadolinium oxide, dysprosium oxide, erbium oxide, ytterbium oxide, cerium oxide, praseodymium oxide, terbium oxide, europium oxide, holmium oxide, thulium oxide, lutetium oxide; f) Pre-synthesized gallium-based functional compounds: zinc gallate, magnesium gallate, cobalt gallate, nickel gallate, copper gallate, iron gallate, indium gallate, aluminum gallate, calcium gallate, strontium gallate, barium gallate, gallium vanadate, gallium molybdate, gallium tungstate, bismuth gallium composite oxide, lithium gallate; g) Precursor compounds The water-insoluble oxalates, carbonates or hydroxides corresponding to each component in a)-f) above decompose in situ during degumming or sintering heat treatment to generate corresponding oxides or oxygen-containing compounds. The water-insoluble means that the solubility in deionized water at 25℃ is ≤0.1g / 100mL. The precursor compound is uniformly dispersed in the form of solid particles during the slurry stage, and decomposes in situ during the heat treatment process to produce nano-sized active powders. The dispersion uniformity is better than that of directly adding oxides. The amount of sintering aid added is 0.2-30 wt.% of the mass of gallium oxide powder: for the sintering aids mentioned in a) to f), it is based on the actual added mass; for the sintering aids mentioned in g), it is based on the theoretical mass of the corresponding oxide generated by complete thermal decomposition, i.e., the oxide equivalent. The defect control agent is a grain growth inhibitor, a valence state compensator, or a grain boundary modifier, selected from at least one of the following components: a) Equivalent substitution stabilizers: with Ga³ + Metal ions with the same valence (M³) + By stabilizing the Ga2O3 lattice through solid solution substitution, Ga³⁺ is suppressed. + Excessive reduction and Ga2O volatilization, including Al2O3, Fe2O3, Cr2O3, In2O3, Sc2O3, and B2O3; b) Donor-type substitution stabilizers: Metal ions Mn with valence state n>3 + Replace Ga³ + This forms a positively charged substitution defect M. Ga •(n-3) Compensating for gallium vacancies V Ga These components inhibit the formation of additional defects, while high-valence oxide grain boundary pinning phases inhibit grain growth, including SnO2, GeO2, SiO2, TiO2, ZrO2, HfO2, Nb2O5, Ta2O5, WO3, MoO3, V2O5, and Sb2O5. c) Acceptor-type substitution stabilizers: divalent metal ions M² + Replace Ga³ + This forms a negatively charged substitution defect M. Ga The oxygen vacancy concentration is regulated to maintain the β-Ga2O3 phase structure; some components form a composite photocatalytic phase, including MgO, ZnO, NiO, CoO, CuO, MnO, FeO, and BeO. d) Grain boundary segregation inhibitors: Elements with large ionic radii inhibit grain growth through grain boundary segregation and solute dragging effects, blocking Ga2O diffusion channels. These include La2O3, Y2O3, Nd2O3, and Pr6O. 11 , Sm2O3, Eu2O3, Gd2O3, Tb4O7, Dy2O3, Ho2O3, Er2O3, Tm2O3, Yb2O3, CeO2, Lu2O3; e) Oxygen activity self-regulating stabilizers: Compounds containing reversible redox pairs maintain the oxidizing atmosphere by dynamically releasing / storing oxygen, thus inhibiting Ga³⁺ oxidation. + Reduction and Ga2O formation, including CeO2, MnO2, Mn2O3, Mn3O4, and Pr6O. 11 , Tb4O7, Co3O4, CoO, Fe2O3, Fe3O4; f) Precursor compounds: The insoluble oxalates and / or carbonates corresponding to components (a)-(e) above have a solubility of ≤0.1g / 100mL in water at 25°C and decompose in situ into the corresponding oxides during sintering; typical precursors include Al2(C2O4)3, FeC2O4, Cr2(C2O4)3, Sc2(C2O4)3, In2(C2O4)3, SnC2O4, ZrOCO3, TiO(C2O4), NbO(C2O4), MgC2O4, ZnC2O4, NiC2O4, CoC2O4, MnC2O4, Ce2(C2O4)3, La2(C2O4)3, Nd2(C2O4)3, Gd2(C2O4)3, and Y2(C2O4)3; The total amount of the defect control agent added is 0.1-15 wt.% of the mass of gallium oxide powder: for components (a) to (e), it is based on the actual added mass; for component (f), it is based on the theoretical mass of the corresponding oxide generated by complete thermal decomposition, i.e., the oxide equivalent.

4. The preparation method according to claim 1, characterized in that, In step S1, the organic additive includes at least one of binders, plasticizers, dispersants, surfactants, rheology modifiers, and defoamers; The organic additives are used alone or in combination, with a total addition amount of 0.1-30 wt.% of the sum of the masses of gallium oxide powder, photocatalytic active components, sintering aids, and defect control agents. The adhesive is selected from any one or more of polyethylene oxide, sodium alginate, chitosan, polyurethane emulsion, polyacrylamide, polyvinyl alcohol, methylcellulose, hydroxypropyl methylcellulose, ethylcellulose, polyethylene glycol, polyacrylic acid, polyvinyl acetate, starch and its derivatives; The plasticizer is selected from any one or more of the following: triethyl acetylglucosamine citrate, epoxidized soybean oil, polycaprolactone, glycerin, dibutyl phthalate, triethyl citrate, polyethylene glycol, sorbitol, and dioctyl sebacate. The dispersant is selected from any one or more of the following: polycarboxylate superdispersant, polymaleic anhydride, polyaspartic acid, ammonium polyacrylate, sodium polyacrylate, tetramethylammonium hydroxide, ammonium citrate, gum arabic, and polyvinylpyrrolidone. The surfactant is selected from any one or more of the following: sorbitan monooleate, cocamidopropyl betaine, perfluoropolyethers, sodium lauryl sulfate, hexadecyltrimethylammonium bromide, polysorbate 80, octylphenyl polyoxyethylene ether, lecithin, and fluorocarbon surfactants. The rheology modifier is selected from any one or more of guar gum, gellan gum, polyacrylic acid thickeners, organic modified montmorillonite, xanthan gum, sodium carboxymethyl cellulose, bentonite, fumed silica and polyacrylamide; The defoamer is selected from one or more of polydimethylsiloxane, polyether defoamer, isooctanol, n-octanol, silicone oil, polyether-modified siloxane, and mineral oil; The pH adjuster is at least one of ammonia and hydrochloric acid; The reinforcing phase is fibers and / or whiskers, selected from any one or more of the following: 1) Inorganic fibers: glass fiber, basalt fiber, silicon carbide fiber, alumina fiber, mullite fiber, quartz fiber, potassium titanate fiber, aluminum nitride fiber; 2) Ceramic whiskers: silicon carbide whiskers, zinc oxide whiskers, calcium sulfate whiskers, silicon nitride whiskers, barium titanate whiskers, aluminum borate whiskers, magnesium borate whiskers, sodium titanate whiskers, potassium titanate whiskers, zirconium oxide whiskers, aluminum oxide whiskers, calcium carbonate whiskers, aluminum nitride whiskers. 3) Natural mineral fibers: sepiolite fiber, attapulgite fiber, wollastonite fiber, palygorskite fiber, tremolite fiber, actinolite fiber, vermiculite fiber, sillimanite fiber, tourmaline fiber; 4) Synthetic organic fibers: polyacrylonitrile fiber, polyvinyl alcohol fiber, aramid fiber, polyimide fiber (completely pyrolyzed during degumming heat treatment, playing a role in pore formation and pre-toughening). 5) Metal whiskers: Tin whiskers, copper whiskers, silver whiskers, nickel whiskers, iron whiskers, zinc whiskers, aluminum whiskers, gold whiskers, platinum whiskers, cobalt whiskers, titanium whiskers, niobium whiskers, zirconium whiskers, tungsten whiskers, molybdenum whiskers, rhenium whiskers, tantalum whiskers, palladium whiskers, chromium whiskers, magnesium whiskers, cadmium whiskers; (6) Metal fibers: stainless steel fiber, copper fiber, aluminum fiber, nickel fiber, titanium fiber, silver fiber, gold fiber, platinum fiber, palladium fiber, iron fiber, steel fiber, tungsten fiber, molybdenum fiber, niobium fiber, tantalum fiber, zirconium fiber, hafnium fiber, magnesium fiber, zinc fiber, tin fiber, lead fiber, cadmium fiber, cobalt fiber, chromium fiber, beryllium fiber, nickel-titanium alloy fiber, iron-chromium-aluminum alloy fiber, nickel-chromium alloy fiber, Invar alloy fiber; Wherein, the aspect ratio of the reinforcing phase is ≥ 10. The gallium oxide-based composite slurry has a solid content of 20-70 vol.% and a pH of 2-14. The amounts of organic additives and reinforcing phases added are based on the total mass of gallium oxide powder, photocatalytically active components, sintering aids, and defect control agents, and are as follows: Adhesive 1-20 wt.%; Dispersant 0.1-5 wt.%; Plasticizer 0.1-10 wt.%; Surfactant 0.01-5 wt.%; Rheology modifier 0.1-10 wt.%; Defoamer 0.05-10 wt.%; pH adjuster 0.01-10 wt.%; Reinforcing phase: 0.01-30 wt.% of fibers or 0.01-50 wt.% of whiskers.

5. The preparation method according to claim 1, characterized in that, In step S1, the homogeneous solution is uniformly dispersed by mechanical stirring; the gallium oxide-based composite slurry is uniformly dispersed by mechanical stirring and / or ball milling. The uniform dispersion of the homogeneous solution is achieved by mechanical stirring at a rate of 10-1800 rpm for 0.1-60 min, using an inert stirring paddle, and maintaining a distance of 0.01-2 cm between the paddle blades and the bottom of the slurry container. When mechanical stirring is used to uniformly disperse the gallium oxide-based suspension slurry and the gallium oxide-based composite slurry, the stirring speed is 20-3000 rpm; the stirring time is 15-1500 min; the stirring paddle is made of inert material; and the distance between the stirring paddle blade and the bottom of the slurry container is 0.1-20 cm. When uniformly dispersing the gallium oxide-based suspension slurry and gallium oxide-based composite slurry using ball milling, the ball milling container used for ball milling is made of an inert material; the ball-to-material weight ratio is 0.2-12; the ball milling time is 30-1500 min; the diameter of a single grinding ball is 0.2-12 mm, and the average diameter is 3-8 mm.

6. The preparation method according to claim 1, characterized in that, In step S2, the organic foam is made of polyurethane, melamine formaldehyde, or polystyrene; the pore density of the organic foam ranges from 6 to 70 PPI, and its macroscopic shape is any one of the following: cylinder, cube, cuboid, sphere, ellipsoid, torus, prism, pyramid, polyhedron, honeycomb block, sheet, arc, arch, tubular, hollow spherical shell, or any combination or deformation thereof. The impregnation is carried out using normal pressure, negative pressure assisted, or alternating negative and normal pressure methods; the impregnation process is carried out at 25±20℃, the normal pressure impregnation time is 30-1800 seconds, and the number of negative and normal pressure alternating impregnations is 1-5 times per impregnation cycle; The negative pressure assistance involves completely immersing the organic foam in the gallium oxide-based composite slurry described in step S1, then evacuating the composite slurry to boiling point within 3 minutes, maintaining boiling for 0.5-10 minutes to ensure that all air in the system is expelled, and then restoring it to ambient pressure. The pressure of the extrusion desizing is controlled at 0.05-5.0 MPa, and the thickness of the organic foam after extrusion is compressed to 30-95% of the original thickness; the centrifugal desizing speed is 500-2000 rpm, and the centrifugation time is 10-600 seconds; The drying process employs a programmed temperature increase method, with a temperature range of 20~95℃ and a relative humidity decreasing from ≥70% to <10%, drying until the mass change rate is <20% / h. After each impregnation-desizing-drying cycle, the mass gain rate of the composite slurry loaded in the organic foam is 50-500%. After 2-5 cycles, the cumulative loading of the composite slurry reaches 150-1000% of the original mass of the organic foam, forming a coating thickness of 0.1-3.0 mm, a coating thickness variation coefficient of <30%, and a pore blockage rate of <40%.

7. The preparation method according to claim 1, characterized in that, In step S3, the natural air drying is carried out in a ventilated environment with a temperature of 5-45℃, a relative humidity of 30-90%, a ventilation rate of 0.1-10.0 m / s, and a natural air drying time of 2-24 hours. The heating program for the drying process is as follows: the temperature is increased from room temperature to 50-95℃ at a rate of 0.01-10.00℃ / min, and the temperature is maintained for 4-8 hours. The airflow rate inside the oven is 0.01-10.00 m / s, and the drying endpoint is a mass change rate of <0.1% / h. The degumming heat treatment includes: The first stage involves raising the temperature at a rate of 1-10℃ / min to 150-250℃ and holding it for 1-360 min. In the second stage, the temperature is increased to 350-450℃ at a rate of 0.5-10℃ / min, and then held for 1-360 min. The third stage involves raising the temperature at a rate of 0.5-10℃ / min to 550-600℃ and holding it for 1-360 min. The degumming heat treatment process is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 100 Pa. The atmospheric conditions are: at least one of helium, argon, nitrogen, ammonia, air and oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50 to +9000 Pa.

8. The preparation method according to claim 1, characterized in that, In step S4, the controlled sintering heat treatment temperature is 900-1700℃, the heating rate is 2-20℃ / min, and the holding time is 0.01-24 hours; The controlled sintering heat treatment is carried out under vacuum or atmospheric conditions. The vacuum conditions are: no gas is introduced and the absolute pressure inside the furnace is maintained below 10 Pa. The atmospheric conditions are: at least one of hydrogen, helium, argon, nitrogen, ammonia, air and oxygen is introduced, the gas flow rate is 0-9000 mL / min, and the pressure inside the furnace is maintained at gauge pressure +50 to +9000 Pa.

9. The monolithic gallium oxide-based photocatalytic foam ceramic obtained by the preparation method according to any one of claims 1 to 8.

10. The monolithic gallium oxide-based photocatalytic foam ceramic prepared by the preparation method according to any one of claims 1 to 8 is used in i) the degradation of organic pollutants or water treatment; ii) in the preparation of an apparatus for degrading organic pollutants or a water treatment apparatus.

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