Preparation method and application of ultra-thin cupric hydroxyl chloride coated titanium dioxide / mxenes photothermal catalytic film

Abstract

This invention belongs to the field of photocatalysis and carbon dioxide resource utilization technology, and relates to a method for preparing and applying an ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film. The photothermal catalytic film comprises: titanium dioxide particles, an ultrathin Cu2(OH)3Cl coating layer in situ coated on its surface to form a T@CCOH photocatalytic material, and a Ti3C2T composite with T@CCOH. x MXenes membrane. The preparation method of this membrane is also disclosed: first, T@CCOH is prepared through an in-situ aging-drying process; then, an MXenes membrane is prepared through etching, stripping, and vacuum filtration; finally, the two are coupled through direct loading or intercalation composite methods. This photothermal catalytic membrane is used for the "nighttime capture-daytime photothermal reduction" process of low-concentration CO2: in the dark, the CCOH layer efficiently adsorbs and enriches CO2; under illumination, TiO2 excites carriers, and the photothermal heating of MXenes promotes reaction kinetics. Without MXenes coupling, the main product is CH4; after coupling, C-C coupling is enhanced, generating multi-carbon products such as C2H4. This invention has advantages such as simple process, high energy utilization, and controllable products.

Description

Technical Field

[0001] This invention belongs to the field of photocatalysis and carbon dioxide resource utilization technology, and relates to composite photocatalytic materials, particularly to a method for preparing and applying an ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film. Technical Background

[0002] Utilizing solar energy to drive the conversion of carbon dioxide (CO2) and water (H2O) into hydrocarbon fuels such as methane (CH4) and ethylene (C2H4) is one of the important technological pathways for achieving "carbon resource recycling" and renewable energy storage. However, existing photocatalytic CO2 reduction systems are mostly carried out under conditions of high-purity CO2 and stable gas supply, making it difficult to adapt to low partial pressure CO2 sources such as air or diluted emission gases. This results in insufficient substrate supply and limited mass transfer in practical applications, leading to a significant decrease in overall reduction rate and energy efficiency.

[0003] In real-world scenarios, CO2 often originates from air (approximately 400 ppm) or diluted industrial exhaust gas, characterized by low concentration, large fluctuations, and significant diurnal variations. Extensive research and engineering practice have shown that under low CO2 concentrations, the CO2 coverage on the catalyst surface is low, making it easier for photogenerated carriers to undergo ineffective recombination or deviate to side reaction pathways. This hinders the conversion of CO2 to multi-electron products (such as CH4), and makes the C–C coupling process required for C2 products (such as C2H4) even more difficult to trigger. Therefore, achieving a stable and continuous CO2 supply under low partial pressure CO2 conditions and coupling it with the photocatalytic conversion process is crucial for advancing this technology towards practical application.

[0004] The traditional "capture-desorption-transport-reaction" route typically relies on amine solutions or solid adsorbents to enrich CO2, followed by desorption via heating or depressurization to transport the CO2 to the reactor. This process is not only complex and energy-intensive, but the separation of the capture agent from the catalyst also leads to CO2 loss during transport, making it difficult to achieve efficient closed-loop utilization of low-concentration CO2. Therefore, there is an urgent need for an integrated capture-conversion catalytic system that can achieve "spontaneous CO2 capture at night and in-situ solar energy conversion of CO2 during the day" at the material level.

[0005] Furthermore, while existing semiconductor photocatalysts (such as TiO2) exhibit good stability, their intrinsic CO2 adsorption and activation capabilities are limited. They also suffer from insufficient active sites and severe carrier recombination, making it difficult to achieve the directional conversion of CO2 into deep reduction products such as CH4 and C2H4. Introducing copper-based active sites can promote multi-electron reduction of CO2 and has the potential to form C2 products. However, common copper species tend to aggregate and have insufficient exposure, making precise control of the interfacial electronic structure difficult. This results in "energy input present but difficult to accurately output to the target reaction pathway," manifesting as selective dispersion, insufficient stability, or difficulty in increasing C2 product yield.

[0006] From an energy utilization perspective, near-infrared (NIR) light constitutes a high proportion (approximately 50%) of sunlight, while most semiconductors primarily respond to ultraviolet / visible light, resulting in insufficient utilization of NIR light and significant heat dissipation. This leads to insufficient overall energy input, localized temperature rise, and inadequate kinetic enhancement of the system. (Two-dimensional Ti3C2T) x MXenes materials possess excellent broad-spectrum absorption and rapid photothermal conversion characteristics. If a stable film interface can be constructed with a photocatalytic active layer, it is expected to achieve two goals: firstly, increasing the effective energy input through the photothermal effect layer; and secondly, promoting the directional flow of charge carriers to copper-based active sites and driving CC coupling to generate C2H4 through the photocatalyst layer. However, to achieve the above synergistic effect, it is necessary to solve problems such as stable composite of the catalyst layer and the photothermal film, interfacial integration, and synergistic mass / heat / electron transfer.

[0007] This invention enhances CO2 adsorption activation and provides stable exposed copper-based sites (T@CCOH) by constructing an ultrathin Cu2(OH)3Cl coating layer (CCOH) in situ on the TiO2 surface, and combines it with Ti3C2T x MXenes photothermal film composites form a full-spectrum driven bilayer or intercalated photothermal catalytic structure (T@CCOH / M), achieving "nighttime capture and daytime photothermal reduction" under low-concentration CO2 sources, and enabling selective expansion of products from CH4 to C2H4. Summary of the Invention

[0008] To address the common technical problems in existing solar-driven CO2 reduction systems under real low-concentration CO2 sources (such as air or diluted emission gases), including insufficient CO2 supply, fragmented capture and conversion, exposure of active sites and low carrier utilization, insufficient near-infrared energy utilization, and difficulty in extending product selectivity from C1 to C2, this invention discloses a method for preparing and applying an ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film.

[0009] Specifically, this invention constructs an ultrathin CCOH coating / intercalation structure in situ on the TiO2 surface. Under dark conditions, it utilizes the hydroxyl-chlorine coordination environment and copper sites on the surface to adsorb and enrich CO2, achieving effective capture of low-partial-pressure CO2 from the air. Under light conditions, the T@CCOH heterostructure provides a higher density of copper-based active sites and promotes interfacial charge separation and transport, enabling the captured CO2 to be rapidly consumed and directionally reduced via multi-electron reduction. Without the introduction of MXenes, the system promotes the deep hydrogenation pathway of CO2, with CH4 as the main product. Further, the T@CCOH catalyst layer is combined with Ti3C2T... xAfter constructing a layered composite film with MXenes, the broadband absorption and photothermal conversion capabilities of MXenes are used to enhance near-infrared energy utilization, accelerate overall reaction kinetics, and increase intermediate coverage, thereby promoting the CC coupling process, increasing the tendency of C2H4 formation, and achieving controllable expansion from C1 products to C2 products.

[0010] Technical solution

[0011] I. Preparation of ultrathin atomic layer coated photocatalysts:

[0012] (I) Preparation of ultrathin Cu2(OH)3Cl nanolayer coated with TiO2 (T@x% CCOH)

[0013] Includes the following steps:

[0014] (1) Precursor dispersion and uniform mixing: TiO2 powder, preferably commercial P25 or anatase TiO2, is added to deionized water to form a suspension. A copper source, selected from CuCl, CuCl2, or a mixture thereof, is added. The suspension is sonicated for 10–60 min, preferably 30 min, to ensure uniform mixing of the copper species with TiO2. The amount of TiO2 used is 200 mg, and the amount of deionized water is 20 mL. The copper source is a copper chloride, nitrate, sulfate, or a mixture thereof with hydrochloric acid, including but not limited to: cuprous chloride (CuCl), copper chloride (CuCl2), copper nitrate [Cu(NO3)2], cuprous nitrate [CuNO3 or Cu2(NO3)2], copper sulfate (CuSO4), and cuprous sulfate (Cu2SO4). Preferably, the copper source is a mixture of cuprous chloride and copper chloride to provide adjustable Cu... + / Cu 2+ Proportion and maintain Cl - The environment promotes the in-situ generation and ultrathin deposition of Cu2(OH)3Cl.

[0015] (2) In-situ electrostatic adsorption pre-assembly: The mixture is transferred to a crucible and aged at room temperature for 1 to 12 hours, preferably 6 hours, so that positively charged Cu species adsorb / complex on the negatively charged TiO2 surface to form nucleation sites.

[0016] (3) Drying and curing: Dry at 70-150℃ for 8-24 h, preferably at 110℃ for 12 h, to promote the generation of CCOH and preferential deposition on the TiO2 surface.

[0017] (4) Washing and low-temperature drying: Wash with deionized water and anhydrous ethanol to remove soluble salts, and then dry at 40-80℃ for 2-12 h, preferably at 60℃ for 6 h, to obtain T@x% CCOH, where x is the mass percentage (relative to TiO2) corresponding to the amount of copper source added, x=1, 3, 5, 7, 9, preferably x=5.

[0018] (II) Introduction of exogenous Cu 2+ Preparation of T@x:y CCOH

[0019] Using CuCl and CuCl2·2H2O as dual copper sources, according to Cu + :Cu 2+ The molar ratio is 1:9 to 9:1, preferably 4:6. The total Cu molar amount corresponds to a 5% loading, which is approximately 0.127 mmol based on 200 mg TiO2. 20 mL of deionized water is added and sonicated for 3 min, followed by the addition of 200 mg TiO2 and sonication for 30 min. Then, the sample is aged, dried, washed, and dried again as per step (I). The sample is named T@x:yCCOH, where x:y represents Cu. + :Cu 2+ The preferred molar ratio is T@4:6 CCOH.

[0020] II. Ti3C2T x Preparation of MXenes photothermal transfer film

[0021] (1) Preparation of etching solution: Inorganic fluoride salt is added to hydrochloric acid to form etching solution, wherein the inorganic fluoride salt is NaF, KF or NH4F; the concentration of hydrochloric acid is 6-12 M; preferably, 2 g LiF is dissolved in a mixed solution of 30 mL 12 M HCl and 10 mL deionized water to obtain a uniform etching solution.

[0022] (2) Selective etching of the MAX phase: Under stirring and temperature control conditions, Ti3AlC2 MAX phase powder is slowly added to the etching solution to react and selectively remove the Al layer. Preferably, the amount of Ti3AlC2 is 2 g; the temperature is 30-50 ℃, preferably 40 ℃; the stirring speed is about 200-600 rpm, preferably 400 rpm; the reaction time is 20-60 h, preferably 40 h, to obtain a black suspension.

[0023] (3) Washing: Dispense the suspension into 50 mL centrifuge tubes, dilute with water to 40 mL, centrifuge at 2000-5000 rpm for 2-10 min and wash repeatedly until the pH of the supernatant is 6-7; preferably, centrifuge at 3500 rpm for 5 min and wash repeatedly until the pH of the supernatant is 6.5.

[0024] (4) Peeling and fractionation centrifugation: The precipitate is dispersed in water and ultrasonically peeled under an inert atmosphere (nitrogen, argon, helium, etc.) and low temperature. Unpeeled large particles are removed by low-speed centrifugation to obtain the supernatant of MXenes nanosheets. Preferably, the precipitate is dispersed in 250 mL of deionized water, ultrasonically treated for 1 h under argon protection and ice bath conditions, and then centrifuged at 2000 rpm for 1 h. The supernatant is then taken as Ti3C2T.x Nanosheet dispersion, concentration approximately 3.2 mg / mL.

[0025] (5) Film formation: MXenes membranes of different qualities are prepared by vacuum filtration and dried at 40-80℃, preferably 60℃, for later use. The filter membrane is PVDF, PTFE or alumina filter membrane.

[0026] III. Preparation of a bilayer coupled photothermal catalytic membrane of T@CCOH and MXenes film

[0027] (I) Directly supported type (upper layer photocatalyst / lower layer MXenes photothermal film)

[0028] Take 10–35 mg of Ti3C2T x The MXenes dispersion was vacuum filtered to form a substrate film; 2 mg T@4:6 CCOH was dispersed in 1 mL of anhydrous ethanol, sonicated, and then vacuum filtered to deposit onto the substrate film surface. The film was dried at 60 °C and denoted as C2 / M. x , where x is the mass of MXenes, preferably 20 mg.

[0029] (II) Intercalation composite type (photocatalyst intercalated between MXenes layers)

[0030] First, filter x mg MXenes to form a base membrane (M x (20-x) mg MXenes dispersion was mixed with 1-5 mg T@4:6 CCOH ethanol dispersion, and the mixture was vacuum filtered and deposited on top of the substrate. The mixture was then dried at 60 °C and denoted as C4@M5 / M. 15 (Where C4 represents 4 mg of photocatalyst, and the actual total MXenes is 20 mg).

[0031] Different compositions can be prepared by adjusting the proportions.

[0032] IV. Application of bilayer coupled photothermal materials in light-driven CO2 reduction

[0033] (I) Operation mode of nighttime CO2 capture - daytime light-driven reduction

[0034] (1) Night / Dark Capture Stage: Under light-free conditions, air or low-concentration CO2 gas flow passes through (or covers) the surface of T@CCOH powder or composite membrane. The Cu2(OH)3Cl ultrathin layer adsorbs and enriches CO2, achieving in-situ carbon storage. The amount of CO2 adsorbed is analyzed by temperature-programmed adsorption-desorption experiments.

[0035] (2) Daytime / Light Conversion Stage: TiO2 undergoes photogenerated carrier excitation under sunlight or xenon lamp irradiation; if MXenes film is introduced, the absorption efficiency in the infrared region is greatly promoted, MXenes generates photothermal effect and enhances reactant transfer, thereby strengthening CO2 conversion efficiency.

[0036] (II) Product performance regulation

[0037] (1) When MXenes are not coupled: the T@CCOH system only responds to ultraviolet-visible light under illumination, with significant heat loss, and CH4 is one of the main reduction products.

[0038] (2) After coupling with MXenes: the composite membrane efficiently absorbs infrared light and rapidly heats up, increasing the surface temperature of the catalyst, accelerating the reaction kinetics, increasing the collision probability of carbon-based intermediates, which is more conducive to carbon-carbon coupling, and improving the yield and selectivity of C2H4.

[0039] V. Material Structure Characterization

[0040] The ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film prepared by the method described in this invention comprises:

[0041] Titanium dioxide particles; an ultrathin basic copper chloride (Cu2(OH)3Cl) coating layer, in situ coated on the surface of the titanium dioxide particles, forming a T@CCOH photocatalytic material; and Ti3C2T x MXenes film, combined with the T@CCOH photocatalytic material;

[0042] The average thickness of the ultrathin basic copper chloride coating layer is 2 Å to 30 Å.

[0043] The morphology of the CCOH coating prepared in this invention can be observed by transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), aberration-scanning transmission electron microscopy (AC-STEM), and energy-dispersive X-ray spectroscopy (EDS mapping); the crystal phase composition and structure can be characterized by X-ray diffraction (XRD); the layered structure of the MXenes film can be observed by cross-section of scanning electron microscopy (SEM).

[0044] The T@CCOH photocatalytic material prepared by the method disclosed in this invention has a morphology of Cu2(OH)3Cl ultrathin nanolayers coated on the surface of granular TiO2, forming a tight heterogeneous interface; further reacting with Ti3C2T x After coupling with the MXenes membrane, the resulting composite membrane material has a morphology of a bilayer structure consisting of an upper T@CCOH photocatalytic layer and a lower MXenes photothermal film layer, or a layered structure consisting of a T@CCOH intercalated composite upper / bottom MXenes film.

[0045] VI. Material Performance Testing

[0046] (1) Dark-state CO2 capture performance test

[0047] A certain amount of T@CCOH powder (or a certain area of ​​T@CCOH / MXenes composite membrane) is placed on the sample tray of a quartz fixed bed or quartz reaction chamber. Before testing, the sample is purged with an inert gas (N2 or Ar) and dried / activated at room temperature to remove weakly adsorbed water and background gas. Under dark conditions, a gas containing CO2 (air with a CO2 volume fraction of 200–1000 ppm and pure CO2 at 100 kPa) is introduced into the device at a constant flow rate to ensure sufficient contact and adsorption of CO2 with the sample. The breakthrough curve is obtained by recording the change in inlet / outlet CO2 concentration over time, and the CO2 adsorption capacity is calculated. The CO2 adsorption capacity and adsorption intensity can be evaluated using CO2 adsorption isotherms and temperature-programmed desorption (CO2-TPD).

[0048] (2) Test of light-driven CO2 reduction performance

[0049] 2.0 mg of photocatalyst was dispersed on the surface of a microporous membrane with a radius of 2.35 cm. 0.5 mL of deionized water was added to the reaction system as a hole-consuming agent. The gas circulation system was then subjected to a 15-minute vacuum treatment, followed by (Method I) filling with high-purity CO2 gas (99.99%) to 90 kPa, or (Method II) directly using the catalyst after dark-state CO2 capture. A 300 W xenon lamp was used as the light source, and the actual irradiation intensity on the catalyst surface was 400 mW·cm². -2 The actual surface temperature of the catalyst was monitored in real time using an infrared thermal imager, and the temperature rise efficiency with and without a photothermal film was compared. Gaseous products were detected by a gas chromatograph equipped with a flame ionization detector (FID) and a thermal conductivity detector (TCD). The generated gases were calibrated using a standard gas mixture, and their composition was qualitatively and quantitatively analyzed by retention time and peak intensity, respectively. Photocatalytic activity experiments were conducted by reducing CO2 under xenon lamp irradiation. The types of reduction products were determined by gas chromatographic retention time, and the CO2 reduction efficiency was determined by comparing the measured peak area with the standard peak area to evaluate the photocatalytic CO2 reduction performance.

[0050] In this invention, the technical term "ultra-thin" refers to an average thickness of 2-30 Å, preferably 5-10 Å, of the CCOH coating layer. The lattice fringes distribution is analyzed using HRTEM and AC-STEM characterization techniques, and the thickness of the outer shell layer is directly measured.

[0051] Beneficial effects

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] (1) Capture-conversion integration: The ultrathin coating of Cu2(OH)3Cl provides CO2 adsorption enrichment and reaction activation sites at the same time, so that low partial pressure CO2 (such as CO2 in the air) can be directly converted after being enriched on the material surface, reducing external concentration energy consumption and system complexity.

[0054] (2) Ultra-thin coating structure improves utilization: an ultra-thin basic copper chloride layer is formed by a mild process of in-situ aging-drying-washing. The preparation process is simple and effectively increases the number of accessible active sites and inhibits the aggregation of copper species.

[0055] (3) MXene interface coupling brings dual gains in photothermal and charge: Ti3C2T x MXenes films provide the ability to conduct rapid photothermal heating, promote carrier separation, accelerate surface reaction kinetics, increase the collision frequency of carbon-based intermediates, and promote carbon-carbon coupling and the generation of multi-carbon products.

[0056] (4) Suitable for day and night cycle scenarios: The material has both dark state capture and light conversion capabilities, and is suitable for the time-sharing operation mode of "carbon absorption at night and light restoration during the day", which is beneficial for outdoor / distributed applications. Attached Figure Description

[0057] Figure 1 (a) TEM image of T@5% CCOH, (b) HRTEM image with local magnification, (c) AC-STEM image of T@4:6 CCOH, (d) AC-STEM image with local magnification; (eh) EDS mapping analysis of Ti, O, Cu and Cl elements corresponding to Figure c.

[0058] Figure 2 (a) XRD patterns of different CCOH loading types on TiO2 surface, (b) XRD patterns magnified locally, (c) Ti3C2T x XRD patterns of MXenes materials;

[0059] Figure 3 (a) SEM image of T@4:6 CCOH, (b) unfiltered Ti3C2T x SEM image of MXenes, (c) T@4:6CCOH / M 20 SEM image of the cross-section of the two-layer material constructed by direct filtration, (d) T@4:6 CCOH@M5 / M 15 SEM image of the cross-section of the intercalated double-layer material;

[0060] Figure 4(a) Comparison of TPD of TiO2 loaded with different CCOH types; (b) Comparison of TPD of CO2 capture in air and pure CO2 by T@4:6 CCOH.

[0061] Figure 5 (a) Comparison of photocatalytic CO2 reduction performance of T@x% CCOH series samples, (b) Comparison of photocatalytic CO2 reduction performance of T@x:y CCOH series samples, (c) Photocatalytic CO2 reduction performance of T@4:6 CCOH after being captured in dark air;

[0062] Figure 6 (a) C2 / M x Comparison of photocatalytic CO2 reduction performance of a series of samples to prepare multi-carbon products, (b) C x @M5 / M 15 Comparison of photocatalytic CO2 reduction performance of a series of samples to prepare multi-carbon products: (c) Surface catalytic temperature of T@4:6 CCOH during photoirradiation; (d) T@4:6 CCOH and Ti3C2T x MXenes membrane intercalation coupling (C4@M5 / M) 15 The surface catalytic temperature during the subsequent light irradiation process. Detailed Implementation

[0063] The present invention will be described in detail below with reference to embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited to the following embodiments.

[0064] Example 1

[0065] Preparation of T@x% CCOH series samples

[0066] 200 mg of TiO2 and 3.1, 9.4, 15.6, 22.0, and 28.0 mg of CuCl were weighed out respectively, and 20 mL of deionized water was added. The mixture was sonicated for 30 min and shaken. The mixture was then transferred to a 50 mL crucible and aged for 6 h. The mixture was dried at 110 ℃ for 12 h. The mixture was washed with deionized water and anhydrous ethanol. The mixture was dried at 60 ℃ for 6 h to obtain T@1% CCOH, T@3% CCOH, T@5% CCOH, T@7% CCOH, and T@9% CCOH.

[0067] like Figure 1 As shown in a and 1b, the TEM images show that commercial TiO2 consists of small nanoparticles. With a 5% Cu2(OH)3Cl loading, HRTEM shows a lattice fringe spacing of 0.193 corresponding to the (116) crystal plane of Cu2(OH)3Cl, and a shell thickness of about 28 Å, indicating the successful construction of Cu2(OH)3Cl coated TiO2 nanoparticles. Figure 2a and 2b show the direct use of Cu + Under the prepared conditions, the (101), (113), and (024) characteristic crystal planes of Cu2(OH)3Cl are clearly visible, while Cu 2+ / Cu + Under certain conditions, the intensity of the (101), (113), and (024) characteristic crystal planes of Cu2(OH)3Cl almost disappears, further indicating that Cu 2+ The introduction weakens Cu + The oxidation process promotes the formation of even thinner Cu2(OH)3Cl, thereby enhancing overall light absorption and utilization of active sites.

[0068] Example 2

[0069] Introducing exogenous Cu 2+ Preparation of T@x:y CCOH under controlled conditions

[0070] Mix CuCl and CuCl2·2H2O according to Cu + :Cu 2+ The molar ratios were 1:9, 3:7, 4:6, 5:5, 7:3, or 9:1 to make the sum of the molar amounts of the two components 0.127 mmol. 20 mL of water was added and the mixture was sonicated for 3 min. 200 mg of TiO2 was added and sonicated for 30 min. The mixture was aged for 6 h, dried at 110 ℃ for 12 h, washed, and dried at 60 ℃ for 6 h to obtain T@5% CuII, T@1:9 CCOH, T@3:7 CCOH, T@4:6 CCOH, T@5:5 CCOH, T@7:3 CCOH, and T@9:1 CCOH.

[0071] like Figure 1 As shown in c and 1d, AC-STEM reveals a lattice fringe spacing of 0.355 nm, corresponding to the (101) crystal plane of TiO2, and the surface is still covered by an ultrathin Cu layer with a shell thickness of only about 5 Å, indicating that the introduction of Cu... 2+ The Cu content was significantly reduced afterward. + The slower, directional oxidation process to form Cu2(OH)3Cl promotes the formation of thinner nanoshells, which in turn facilitates light transmission and exposes more atomic sites; EDS Mapping ( Figure 1 The results show a uniform distribution of Ti, O, Cu, and Cl elements in the T@4:6 CCOH material, further illustrating the construction of the Cu2(OH)3Cl-coated TiO2 catalyst.

[0072] Example 3

[0073] Ti3C2T x MXenes Nanosheets and Membrane Preparation

[0074] 2 g LiF was dissolved in a mixed solution of 30 mL 12 M HCl and 10 mL deionized water to obtain a homogeneous etching solution. Ti3AlC2 was etched for 40 h at 40 ℃ and 400 rpm with stirring. The solution was washed until pH 6.5, and then ultrasonically exfoliated in an argon-ice bath for 1 h. The supernatant was collected by centrifugation at 2000 rpm for 1 h. The solution was then vacuum filtered to form a film and dried at 60 ℃ for later use.

[0075] like Figure 3 As shown in a and 3b, T@4:6 CCOH has an overall nanoparticle morphology, while Ti3C2T x MXenes exist in the form of two-dimensional nanosheets and have relatively large pores when not filtered. Furthermore... Figure 2 c displays Ti3C2T x The (002) characteristic crystal plane indicates that Ti3C2T x The successful construction of MXenes.

[0076] Example 4

[0077] C2 / M 20 Preparation of composite photothermal catalytic membrane

[0078] First, take 20 mg Ti3C2T x MXenes were vacuum filtered to form a substrate; then 2 mg T@4:6 CCOH was dispersed in 1 mL of ethanol and sonicated; the substrate was directly deposited onto the substrate by vacuum filtration and then further filtration was performed to integrate the interface; the substrate was dried at 60 °C to obtain C2 / M 20 .

[0079] Figure 3 c shows that 2 mg of nanoparticle photocatalyst was directly filtered and loaded onto 20 mg of Ti3C2T. x On the MXenes surface, surface photocatalyst nanoparticles exist in a large stacked form.

[0080] Example 5

[0081] C2@M5 / M 15 Composite membrane preparation

[0082] 15 mg Ti3C2T was first deposited at the bottom by filtration. x MXenes form the substrate film; 5 mg Ti3C2T x The MXenes dispersion was mixed thoroughly with 2 mg of T@4:6 CCOH ethanol dispersion; the mixture was then vacuum filtered and deposited onto the pre-formed Ti3C2T. x Top the MXenes film and dry at 60 °C to obtain C4@M5 / M 15 .

[0083] Figure 3 d shows the photocatalyst intercalation into Ti3C2T x MXenes nanosheets are uniformly dispersed and co-deposited on a tightly packed layered Ti3C2T matrix. x MXenes substrate surface.

[0084] Example 6

[0085] High-purity CO2 adsorption performance test of photocatalyst

[0086] Weigh 50 mg of sample (TiO2, Cu2(OH)3Cl, T@5% CCOH, T@4:6 CCOH) and place it in a reaction tube. Pre-dry the sample by increasing the temperature from room temperature to 300 °C at a rate of 10 °C / min. Purge with He gas (30 mL / min) for 1 h. Cool to 50 °C and introduce high-purity CO2 gas (30 mL / min) for 1 h until saturation. Purge with He gas (30-50 mL / min) for 1 h to remove weakly adsorbed CO2 on the surface. Finally, desorb the sample by increasing the temperature to 400 °C at a rate of 10 °C / min under He atmosphere. Detect the desorbed gas using a TCD.

[0087] like Figure 4 As shown in Figure a, TiO2 exhibits the lowest CO2 adsorption capacity (0.795 × 10⁻⁶). 17 / mg); when 5% Cu2(OH)3Cl was loaded onto the surface, the CO2 adsorption capacity increased to 2.505×10 17 / mg; while when Cu 2+ The introduction of this substance reduced the overall CO2 adsorption capacity to 1.857 × 10⁻⁶. 17 / mg; Cu2(OH)3Cl alone showed the highest CO2 adsorption capacity (19.88×10⁻⁶ mg); 17 The figure (mg / mg) indicates that CCOH coating significantly enhances CO2 adsorption capacity.

[0088] Example 7

[0089] Test of CO2 adsorption performance of photocatalyst in air

[0090] Weigh 50 mg of sample T@4:6 CCOH and place it in a reaction tube. Place it in air (CO2 concentration approximately 400 ppm) and let it stand in the dark for 12 h. Then, switch to a He gas flow (30-50 mL / min) to purge for 1 h to remove the weakly physically adsorbed CO2 on the surface. Finally, desorb the CO2 at a He atmosphere with a heating rate of 10 ℃ / min to 400 ℃. Detect the desorbed gas using a TCD.

[0091] like Figure 4As shown in b, T@4:6 CCOH shows 0.122 × 10 17 With a CO2 adsorption capacity of / mg, this material demonstrates that it can accurately capture and enrich CO2 even at ultra-low CO2 concentrations (400 ppm).

[0092] Example 8

[0093] Photocatalyst performance testing under high-purity CO2 environment

[0094] 2.0 mg of T@5% CCOH and T@4:6 CCOH photocatalysts were dispersed on the surface of a microporous membrane with a radius of 2.35 cm. 0.5 mL of deionized water was added to the reaction system as a hole-consuming agent. The gas circulation system was then subjected to a 15-minute vacuum treatment, followed by filling with high-purity CO2 gas (99.99%) to 90 kPa. A 300 W xenon lamp was used, resulting in an actual light intensity of 400 mW·cm⁻¹ on the catalyst surface. -2 Continuous irradiation for 6 hours.

[0095] like Figure 5 As shown in a and 5b, the T@5% CCOH and T@4:6 CCOH photocatalysts showed performance values ​​of 3.7 mmol·g after 6 h of testing. -1 ·h -1 and 6.9 mmol·g -1 ·h -1 The CH4 generation rate was 694 times and 1278 times that of the monomer TiO2, respectively.

[0096] Example 9

[0097] Dark-state air CO2 capture - Daytime light-driven photocatalyst performance test

[0098] 2.0 mg of T@4:6 CCOH photocatalyst was dispersed on the surface of a microporous membrane with a radius of 2.35 cm. 0.5 mL of deionized water was added to the reaction system as a hole-consuming agent. Furthermore, the catalyst, after being left to stand in the air for 12 h in the dark to capture CO2, was placed directly in the system. The gas circulation system was then subjected to a 15-minute vacuum treatment. A 300 W xenon lamp was used as the light source, and the actual light intensity irradiated onto the catalyst surface was 400 mW·cm². -2 .

[0099] like Figure 5 As shown in c, after the material was placed in darkness for 12 h and then exposed to light for 12 h, the cumulative CH4 formation reached as high as 26.2 mmol·g⁻¹ in the first cycle. -1 And on the fifth day, it still had a high level of 19.3 mmol / g. -1The low cumulative CH4 production indicates that the catalyst has excellent directional CO2 capture capability and excellent catalytic stability.

[0100] Example 10

[0101] Catalytic performance testing of a photocatalyst-supported photothermal film bilayer system under high-purity CO2 conditions

[0102] 2.0 mg of T@4:6 CCOH photocatalyst was directly added to 20 mg of Ti3C2T. x MXenes membrane surface (C2 / M) 20 Subsequently, 0.5 mL of deionized water was added to the reaction system as a hole-consuming agent. In addition, the gas circulation system was vacuum-treated for 15 minutes, followed by filling with high-purity CO2 gas (99.99%) to 90 kPa. A 300 W xenon lamp was used, with an actual catalyst surface irradiation intensity of 400 mW·cm⁻¹. -2 Continuous irradiation for 6 hours.

[0103] like Figure 6 As shown in a, C2 / M 10 The photocatalyst / photothermal film bilayer system showed a performance of 1.8 mmol·g after 6 h of performance testing. -1 ·h -1 and 1.0 mmol·g -1 ·h -1 The formation rates of C2H4 and C2H6.

[0104] Example 11

[0105] Catalytic performance testing of a photocatalyst intercalated supported photothermal film bilayer system under high-purity CO2 environment

[0106] 4.0 mg of T@4:6 CCOH photocatalyst was pre-assembled and intercalated into 5 mg of Ti3C2T x MXenes form a precursor, which is then filtered to 15 mg of Ti3C2T. x MXenes membrane surface (C4@M5 / M) 20 Subsequently, 0.5 mL of deionized water was added to the reaction system as a hole-consuming agent. In addition, the gas circulation system was subjected to a 15-minute vacuum treatment, followed by filling with high-purity CO2 gas (99.99%) to 90 kPa. A 300 W xenon lamp was used, with an actual catalyst surface irradiation intensity of 400 mW·cm⁻¹. -2 Continuous irradiation for 6 hours.

[0107] like Figure 6 As shown in b, C4@M5 / M 20The photocatalyst / photothermal film bilayer system showed a performance of 2.3 mmol·g after 6 h of performance testing. -1 ·h -1 and 1.3 mmol·g -1 ·h -1 The C2H4 and C2H6 generation rates were 15 and 44 times higher, respectively, than those of the single T@4:6 CCOH photocatalyst; and Figure 6 c and 6d show that the highest reaction temperature on the surface of a single T@4:6 CCOH photocatalyst is 60.5℃, while C4@M5 / M 20 The highest surface reaction temperature in the photocatalyst / photothermal film bilayer system was 193.4℃, indicating that the photothermal effect can greatly promote molecular motion, increase the frequency of molecular collisions, promote C-C coupling, and promote the preparation of multi-carbon products.

[0108] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic membrane, characterized in that, include: Titanium dioxide particles; an ultrathin basic copper chloride Cu2(OH)3Cl coating layer, in situ coated on the surface of the titanium dioxide particles, forming a T@CCOH photocatalytic material; and Ti3C2T x The MXenes membrane is composited with the T@CCOH photocatalytic material; wherein the average thickness of the ultrathin basic copper chloride coating layer is 2 Å to 30 Å.

2. The ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic membrane according to claim 1, characterized in that: The average thickness of the ultrathin basic copper chloride coating is 5 Å to 10 Å; the Ti3C2T x The MXenes film forms a direct-supported structure or an intercalated composite structure with the T@CCOH photocatalytic material; the direct-supported structure is: Ti3C2T x MXenes membrane serves as the substrate, with T@CCOH photocatalyst material loaded on its surface; the intercalated composite structure is: Ti3C2T x The MXenes membrane comprises a base film and an intercalated composite top layer, wherein the intercalated composite top layer is composed of Ti3C2T x The mixture of MXenes and T@CCOH photocatalytic material is deposited on the surface of the substrate.

3. A method for preparing an ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 1 or 2, characterized in that, Includes the following steps: (1) Preparation of T@CCOH photocatalytic material with ultrathin Cu2(OH)3Cl nanolayer coated TiO2; (2) Preparation of Ti3C2T x MXenes photothermal film; (3) Combine the T@CCOH photocatalyst material obtained in step (1) with the Ti3C2T obtained in step (2). x The ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film is obtained by combining MXenes photothermal film with MXenes photothermal film.

4. The method for preparing the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 3, characterized in that, The preparation of the T@CCOH photocatalytic material in step (1) includes: (a) Disperse TiO2 powder in deionized water, add copper source, and mix ultrasonically to obtain precursor suspension; (b) The precursor suspension is aged at room temperature for 1–12 h; (c) Dry the aged product at 70–150°C for 8–24 h; (d) After washing, dry at 40–80 °C to obtain T@CCOH photocatalytic material; The copper source is preferably a mixture of cuprous chloride and cupric chloride, and Cu + With Cu 2+ The molar ratio is 1:9 to 9:1, more preferably 4:

6.

5. The method for preparing the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 3, characterized in that, The Ti3C2T mentioned in step (2) x The preparation of MXenes photothermal films includes: (i) Inorganic fluoride salts are added to hydrochloric acid to form an etching solution, and Ti3AlC2 MAX phase powder is selectively etched to obtain etching products; (ii) Wash the etching product until the pH is 6-7; (iii) Under inert atmosphere and low temperature conditions, ultrasonic peeling and centrifugation were performed to obtain Ti3C2T. x MXenes nanosheet dispersion; (iv) The Ti3C2T x The MXenes nanosheet dispersion was vacuum filtered to form a film, which was then dried to obtain Ti3C2T. x MXenes photothermal film.

6. The method for preparing the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 3, characterized in that, The composite process described in step (3) employs either the direct loading method or the intercalation composite method; wherein, The direct loading method is as follows: first, Ti3C2T... x The MXenes dispersion was vacuum filtered to form a substrate film, and then the T@CCOH photocatalytic material dispersion was vacuum filtered and deposited on the surface of the substrate film, followed by drying. The intercalation composite method is as follows: first, vacuum filtration is used to form Ti3C2T. x MXenes base film, then Ti3C2T x The MXenes dispersion and the T@CCOH photocatalytic material dispersion were mixed and vacuum filtered together to deposit on the surface of the substrate film, and then dried.

7. An application of the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 1 or 2 in solar-driven carbon dioxide reduction, characterized in that: The photothermal catalytic membrane is used for the integrated process of capturing and photothermal catalytic reduction of low-concentration carbon dioxide.

8. The application of the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 7 in solar-driven carbon dioxide reduction, characterized in that: The application includes a nighttime capture phase and a daytime photothermal reduction phase; The nighttime capture stage is as follows: under no-light conditions, air or a low-concentration carbon dioxide stream is passed through the photothermal catalytic membrane, and the basic copper chloride coating layer adsorbs and enriches the carbon dioxide. The daytime photothermal reduction stage is as follows: Under illumination, titanium dioxide in the photothermal catalytic film generates photogenerated carriers, Ti3C2T x MXenes membranes absorb infrared light and generate a photothermal effect, reducing captured carbon dioxide into hydrocarbons.

9. The application of the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 8 in solar-driven carbon dioxide reduction, characterized in that: When the photothermal catalytic membrane is a T@CCOH photocatalytic material without MXenes coupling, the main reduction product is methane; when the photothermal catalytic membrane is a mixture of T@CCOH and Ti3C2T... x When using MXenes composite membranes, the reduction products include ethylene.

10. The application of the ultrathin basic copper chloride-coated titanium dioxide / MXenes photothermal catalytic film according to claim 7 in solar-driven carbon dioxide reduction, characterized in that: The low-concentration carbon dioxide is a gas with a volume fraction of 200–1000 ppm.

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