A GO-coupled modified g-C3N4 photocatalyst, its preparation method and application

Abstract

This invention belongs to the field of photocatalytic water splitting for hydrogen production, specifically relating to a GO-coupled modified g-C3N4 photocatalyst, its preparation method, and its application. Layered stacked g-C3N4 is dispersed in a solvent and subjected to a first ultrasonic exfoliation to obtain a g-C3N4 dispersion. Graphene oxide is added to the g-C3N4 dispersion, followed by a second ultrasonic exfoliation to allow the graphene oxide and g-C3N4 to undergo π-π stacking and hydrogen bonding. After solid-liquid separation and drying, a composite structure is formed, which is then ground to a particle size ≤75μm to obtain the GO-coupled modified g-C3N4 photocatalyst. This invention utilizes a physical blending method to achieve a strong interfacial bond between GO and g-C3N4 through π-π stacking and hydrogen bonding, increasing the number of active sites. Furthermore, the introduction of pore defects through grinding reduces carrier recombination, extends carrier lifetime, and exhibits excellent stability.

Description

Technical Field

[0001] This invention belongs to the field of photocatalytic water splitting for hydrogen production technology, specifically relating to a GO-coupled modified g-C3N4 photocatalyst, its preparation method, and its application. Background Technology

[0002] Photocatalytic water splitting and hydrogen evolution technology can directly utilize solar energy to convert water into hydrogen gas, which has advantages such as low energy consumption and environmental friendliness. High-efficiency photocatalysts are the core of the industrialization of this technology. Graphite phase carbon nitride (g-C3N4) is a non-metallic semiconductor photocatalyst with advantages such as visible light response (band gap of about 2.7 eV), low preparation cost, good chemical stability and no heavy metal pollution. It is widely used in the field of photocatalytic hydrogen evolution. However, pure g-C3N4 has three major defects that seriously limit its performance: (1) High recombination rate of photogenerated carriers: valence band holes and conduction band electrons are easy to recombine inside the material or on the surface, resulting in a small number of effective carriers; (2) Slow electron transfer rate: poor conductivity, photogenerated electrons are difficult to migrate quickly to the surface to participate in the hydrogen evolution reaction; (3) Small specific surface area: pure g-C3N4 is a stacked aggregate structure with a specific surface area of ​​only about 10 m². 2 / g, insufficient number of active sites, weak water molecule adsorption capacity.

[0003] To address these issues, existing technologies often employ modification methods such as non-metallic element doping (e.g., B, P, S), heterostructure construction (e.g., compositing with metal sulfides), and morphology manipulation (e.g., porosimetry). For example, non-metallic doping can narrow the band gap and adjust electron distribution, but single doping has limited effect on improving surface charge separation efficiency. Reduced graphene oxide (rGO) is used for composite modification due to its good conductivity, but rGO has few oxygen-containing functional groups on its surface, resulting in weak interfacial bonding with g-C3N4 and insufficient electron trapping ability. Summary of the Invention

[0004] The purpose of this invention is to provide a GO-coupled modified g-C3N4 photocatalyst, its preparation method, and its application, so as to solve the problems of fast carrier recombination, slow electron transfer, and insufficient active sites in pure g-C3N4, and to achieve a significant improvement in photocatalytic hydrogen evolution performance.

[0005] To achieve the above objectives, the specific technical solution provided by the present invention is as follows: The first objective of this invention is to provide a method for preparing a GO-coupled modified g-C3N4 photocatalyst, comprising the following steps: The layered stacked structure of g-C3N4 was dispersed in a solvent and subjected to a first ultrasonic exfoliation to obtain a g-C3N4 dispersion. Graphene oxide was added to the g-C3N4 dispersion and subjected to a second ultrasonic exfoliation to allow the graphene oxide and g-C3N4 to undergo π-π stacking and hydrogen bonding. After solid-liquid separation, the mixture was dried to form a composite structure, which was then ground to a particle size ≤75μm, resulting in a composite structure containing pore defects with a pore size of 4nm to 20nm, thus obtaining a GO-coupled modified g-C3N4 photocatalyst.

[0006] Furthermore, the mass ratio of graphene oxide to g-C3N4 is 0.1 to 4:100.

[0007] Furthermore, the specific surface area of ​​g-C3N4 is 10.0 m². 2 / g~10.5m 2 / g, the ratio of the characteristic peak intensity of the (100) crystal plane to that of the (002) crystal plane is 1:8~10.

[0008] Furthermore, the thickness of graphene oxide is 1nm–5nm, the sheet diameter is 3μm–8μm, and the D... 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g.

[0009] Furthermore, the frequency of the first and second ultrasonic ablation was 40kHz, the power was 300W, and the time was 1h to 3h.

[0010] Furthermore, the preparation method of g-C3N4 with a layered stacked structure includes the following steps: Melamine was used as raw material and calcined at 540℃~560℃ in air atmosphere. After calcination, the material was ground to a particle size ≤75μm to obtain g-C3N4 with a layered stacked structure. The heating rate during calcination was 4℃ / min~6℃ / min and the calcination time was 3.5h~4.5h.

[0011] The second objective of this invention is to provide a GO-coupled modified g-C3N4 photocatalyst, which is prepared using the above-described preparation method.

[0012] Furthermore, the photocatalyst uses g-C3N4 sheets as a support to support graphene oxide, and the specific surface area of ​​the photocatalyst is 10.55 m². 2 / g~15.52m 2 / g, with an interlayer spacing of 0.320nm~0.322nm and a band gap of 2.45eV~2.58eV.

[0013] The third objective of this invention is to provide the application of GO-coupled modified g-C3N4 photocatalyst in photocatalytic water splitting for hydrogen production. The GO-coupled modified g-C3N4 photocatalyst is dispersed in an aqueous solution containing a sacrificial agent, a platinum source is added to perform photodeposition of platinum, and then a photocatalytic reaction is carried out under visible light irradiation and a protective atmosphere.

[0014] Furthermore, the sacrificial agent is triethanolamine, and the volume concentration of the sacrificial agent in the aqueous solution is 10%; the loading of platinum in the catalyst is 3.0 wt%.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes a physical blending method to modify graphene oxide (GO) and couple it with g-C3N4, resulting in a strong interfacial bond between GO and g-C3N4 through π-π stacking and hydrogen bonding. The oxygen-containing functional groups in GO promote electron transfer, significantly reducing EIS impedance and thus increasing photocurrent density. Simultaneously, the layered stacking structure of g-C3N4 effectively inhibits GO aggregation. By introducing pore defects through grinding, the specific surface area is increased, the number of active sites is enhanced, the band gap is reduced, and the light absorption range is expanded, thereby improving solar energy utilization efficiency. Furthermore, the addition of GO effectively suppresses photogenerated carrier recombination and extends carrier lifetime. This composite photocatalyst exhibits excellent stability, showing no significant performance degradation after four cycles, and poses no risk of heavy metal leaching, making it environmentally friendly. When the GO content is 2.0 wt%, the hydrogen evolution rate reaches 1229.1 μmol·g⁻¹. -1 ·h -1 It is pure g-C3N4 (416.8 μmol·g). -1 ·h -1 It is 2.95 times that of [previous product]. The preparation process is simple, low-cost, and environmentally friendly, and can be applied on a large scale to green hydrogen production. Attached Figure Description

[0016] Figure 1 This is a process flow diagram of the GO-coupled modified g-C3N4 photocatalyst of the present invention.

[0017] Figure 2 The images show the microstructures of the GO-coupled modified g-C3N4 photocatalyst prepared in Example 4 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 2 In the image, (a) is a scanning electron microscope (SEM) image of GO, (b) is a scanning electron microscope (SEM) image of g-C3N4 photocatalyst, (c) is a scanning electron microscope (SEM) image of 2%GO-g-C3N4 photocatalyst, (d) is a transmission electron microscope (TEM) image of GO, (e) is a TEM image of g-C3N4 photocatalyst, and (c) is a TEM image of 2%GO-g-C3N4 photocatalyst.

[0018] Figure 3The image shows the XRD patterns of the g-C3N4 and GO-coupled modified g-C3N4 photocatalysts of this invention.

[0019] Figure 4 The images show the adsorption isotherms of g-C3N4 and GO-coupled modified g-C3N4 photocatalysts of this invention. Figure 4 In the diagram, (a) represents GO and (b) represents g-C3N4.

[0020] Figure 5 This is the adsorption isotherm diagram of the GO-coupled modified g-C3N4 photocatalyst of this invention. Figure 5 In the above, (a) is a 0.1% GO-g-C3N4 photocatalyst, (b) is a 0.5% GO-g-C3N4 photocatalyst, (c) is a 1% GO-g-C3N4 photocatalyst, (d) is a 2% GO-g-C3N4 photocatalyst, and (e) is a 4% GO-g-C3N4 photocatalyst.

[0021] Figure 6 The visible light absorption diagrams of the GO-coupled modified g-C3N4 photocatalyst and the g-C3N4 photocatalyst of this invention are shown.

[0022] Figure 7 This is a bandgap diagram of the GO-coupled modified g-C3N4 photocatalyst and the g-C3N4 photocatalyst of the present invention. Figure 7 In the figure, (a) is the bandgap width curve and (b) is the bandgap distribution diagram.

[0023] Figure 8 The images show the FTIR spectra of the GO-coupled modified g-C3N4 photocatalyst and the g-C3N4 photocatalyst of this invention. Figure 8 In the image, (a) represents the g-C3N4 photocatalyst and GO, and (b) represents the GO-coupled modified g-C3N4 photocatalyst.

[0024] Figure 9 XPS spectra of the GO-coupled modified g-C3N4 photocatalyst prepared in Example 4 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 9 In the image, (a) is the full spectrum, (b) is the C 1s spectrum of GO, (c) is the O 1s spectrum of GO, (d) is the C 1s spectrum of g-C3N4, (e) is the N 1s spectrum of g-C3N4, (f) is the O 1s spectrum of g-C3N4, (g) is the C 1s spectrum of 2%GO-g-C3N4 photocatalyst, (h) is the N 1s spectrum of 2%GO-g-C3N4 photocatalyst, and (i) is the O 1s spectrum of 2%GO-g-C3N4 photocatalyst.

[0025] Figure 10The figures show the hydrogen evolution performance of the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 10 (a) is the hydrogen evolution rate curve, (b) is the hydrogen evolution rate curve, and (c) is the cycle diagram of the 2% GO-g-C3N4 photocatalyst.

[0026] Figure 11 The electrochemical impedance spectroscopy (EIS) spectra of the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 of this invention and the g-C3N4 photocatalysts prepared in Comparative Example 1 are shown.

[0027] Figure 12 The transient photocurrent response diagrams are for the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 of this invention and the g-C3N4 photocatalysts prepared in Comparative Example 1. Detailed Implementation

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0030] Graphene oxide (GO) is a two-dimensional layered material with abundant oxygen-containing functional groups (hydroxyl, carboxyl, and epoxy groups), an ultra-large specific surface area, and excellent electronic conductivity. Its oxygen-containing functional groups can form strong interactions with g-C3N4 (such as hydrogen bonds and π-π stacking), promoting interfacial electron transfer. Simultaneously, GO can act as an "electron bridge," capturing photogenerated electrons from g-C3N4 and reducing carrier recombination. Furthermore, the layered structure of GO can inhibit g-C3N4 aggregation, increasing its specific surface area. Based on this, the present invention provides a GO-modified g-C3N4 with precise coupling. Through π-π stacking and hydrogen bonding of GO and g-C3N4, the layered structure inhibits agglomeration, increases the specific surface area by 50%, increases the number of active sites, and the oxygen functional groups contained in GO promote electron transfer. The EIS impedance is significantly reduced (the Nyquist arc radius is the smallest), and the photocurrent density is increased by more than 2 times. Furthermore, the particle size is ground to ≤75μm, so that the composite structure contains pore defects with a pore size of 4nm to 20nm, which reduces carrier recombination and prolongs carrier lifetime.

[0031] Specifically, a method for preparing a GO-coupled modified g-C3N4 photocatalyst includes the following steps: The layered stacked structure of g-C3N4 was dispersed in a solvent and subjected to a first ultrasonic exfoliation to obtain a g-C3N4 dispersion. GO was added to the g-C3N4 dispersion and subjected to a second ultrasonic exfoliation to allow GO and g-C3N4 to undergo π-π stacking and hydrogen bonding. After solid-liquid separation, the mixture was dried to form a composite structure, which was then ground to a particle size ≤75μm, resulting in a composite structure containing pore defects with a pore size of 4nm to 20nm, thus obtaining a GO-coupled modified g-C3N4 photocatalyst.

[0032] In this invention, GO is modified and coupled with g-C3N4 through physical blending, resulting in a strong interfacial bond between GO and g-C3N4 through π-π stacking and hydrogen bonding. The oxygen-containing functional groups of GO promote electron transfer, significantly reducing EIS impedance and thus increasing photocurrent density. Simultaneously, the layered stacking structure of g-C3N4 inhibits GO aggregation, increases specific surface area, and increases the number of active sites. Furthermore, the introduction of pore defects through grinding reduces carrier recombination and prolongs carrier lifetime, exhibiting excellent stability. Performance shows no significant degradation after four cycles, and there is no risk of heavy metal leaching, making it environmentally friendly. In some embodiments, the mass ratio of GO to g-C3N4 is 0.1–4:100. When the GO content is 2 wt%, the hydrogen evolution rate reaches 1229.1 μmol·g⁻¹. -1 ·h -1 It is pure g-C3N4 (416.8 μmol·g). -1 ·h -1 The electron transfer resistance (approximately 260Ω) is only 1 / 3 that of pure g-C3N4 (approximately 780Ω) when the GO content is 2.95 times that of pure g-C3N4 (approximately 780Ω), and the photocurrent density (0.125mA / cm²) is 2.95 times that of pure g-C3N4 (approximately 780Ω). 2 ) is pure g-C3N4 (0.062 mA / cm 2 The hydrogen evolution rate was twice that of the initial value; after four cycles (cumulative 20 hours), the hydrogen evolution rate remained at 91.5% of the initial value (1125.1 μmol·g⁻¹). -1 ·h -1 It is superior to "metal-doped g-C3N4 (performance degradation >20% after 3 cycles). The preparation process is simple, low-cost, and environmentally friendly, and can be applied on a large scale to green hydrogen production."

[0033] In some embodiments, the specific surface area of ​​g-C3N4 is 10.0 m². 2 / g~10.5m 2 / g, the characteristic peak intensity ratio of the (100) crystal plane to the (002) crystal plane is 1:8~10. The preparation method of the layered stacked structure g-C3N4 includes the following steps:

[0034] Melamine was used as raw material and calcined at 540℃~560℃ in air atmosphere. After calcination, the material was ground to a particle size ≤75μm to obtain g-C3N4 with a layered stacked structure. The heating rate during calcination was 4℃ / min~6℃ / min and the calcination time was 3.5h~4.5h.

[0035] In this invention, melamine is used as the sole precursor, and g-C3N4 layered stacked structure is prepared by thermal polymerization. By controlling the calcination process parameters, the integrity of the g-C3N4 layered structure and the appropriate band gap (~2.58 eV) are ensured, avoiding the collapse or agglomeration of the g-C3N4 layered structure. As a preferred embodiment of this invention, the purity of melamine is >99%. During calcination, melamine is placed in a covered alumina crucible with a gap of ≤2 mm between the crucible lid and the crucible to prevent the volatilization of the precursor during calcination, which would lead to an increase in g-C3N4 crystal defects. During calcination, the temperature is increased from room temperature to 550℃ at a heating rate of 5℃ / min (too fast a heating rate will cause the g-C3N4 layered structure to collapse, while too slow a rate will cause the precursor to agglomerate). The calcination is carried out at a constant temperature of 550℃ for 4 hours, followed by natural cooling to room temperature. The g-C3N4 powder is then ground to a particle size of ≤75μm using an agate mortar to ensure uniform particle size and avoid uneven dispersion caused by large particles. This lays the foundation for uniform dispersion for subsequent interfacial directional coupling with GO. At the same time, pore defects with a pore size of 4~20nm are introduced during the grinding process to reduce photogenerated carrier recombination and improve photocatalytic hydrogen evolution performance.

[0036] In some embodiments, the thickness of GO is 1 nm to 5 nm, the flake diameter is 3 μm to 8 μm, and D 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g. In this invention, by maintaining a monolayer / few-layer structure of GO, the exposure of oxygen-containing functional groups (hydroxyl, carboxyl, epoxy groups) can be maximized, providing sufficient sites for strong interfacial bonding with g-C3N4 through π-π stacking and hydrogen bonding. By controlling the particle size of GO, sufficient loading substrate area is provided for g-C3N4 to ensure adequate contact between the two, while avoiding GO agglomeration due to excessively large particle size (>8μm) or reducing effective contact sites with g-C3N4 due to excessively small particle size (<3μm), thus ensuring the continuity of electron transfer channels. By controlling the median particle size of GO, uniform particle size distribution of GO powder can be ensured, avoiding local agglomeration during dispersion caused by the presence of large GO particles, ensuring overall uniform particle size after mixing with g-C3N4, and improving the stability of catalyst performance. By controlling the specific surface area of ​​GO, sufficient loading sites are provided for g-C3N4, significantly increasing the number of photocatalytic active sites.

[0037] In some embodiments, the frequency of the first and second ultrasonic ablation is 40 kHz, the power is 300 W, and the time is 1 h to 3 h. In this invention, before the first ultrasonic ablation, the layered stacked structure of g-C3N4 is dispersed in deionized water, wherein the mass ratio of g-C3N4 to deionized water is 1 g: 50 mL. The temperature is controlled at 25 °C to 35 °C during ultrasonication. After ultrasonication, the mixture is allowed to stand for 30 min with magnetic stirring at 200 r / min to form a g-C3N4 dispersion. The purpose of the first ultrasonic ablation is twofold: first, to break the layered aggregate structure of g-C3N4, achieve layered dispersion, increase the effective specific surface area, and expose more active sites; second, to allow g-C3N4 to be uniformly dispersed in water, providing sufficient contact area for subsequent strong interfacial bonding with GO through π-π stacking and hydrogen bonding.

[0038] In this invention, after the second ultrasonic exfoliation, solid-liquid separation is performed. This separation is carried out under a vacuum of -0.09 MPa to -0.1 MPa using a 0.45 μm pore size polyvinylidene fluoride (PVDF) microporous membrane, collecting the filter cake with a moisture content controlled at 15%–20%. The filter cake is then placed in an electrically heated drying oven with a temperature control accuracy of ±1℃ and dried at a constant temperature of 70±5℃ in air for 12 hours, resulting in a moisture content of ≤5%. Subsequently, the dried product is ground to a particle size ≤75 μm. During the coupling process, GO and g-C3N4 form chemical interactions through π-π stacking and hydrogen bonding.

[0039] In addition, this invention also provides a GO-coupled modified g-C3N4 photocatalyst, wherein the photocatalyst uses g-C3N4 sheets as a support and loads GO sheets, and the specific surface area of ​​the photocatalyst is 10.55 m². 2 / g~15.52m 2 / g, which is 1.05 to 1.5 times that of pure g-C3N4; the interlayer spacing is 0.320 nm to 0.322 nm, which is 0.003 nm to 0.005 nm smaller than that of pure g-C3N4 (0.325 nm); the band gap is 2.45 eV to 2.58 eV, and the visible light absorption edge is 458 nm to 474 nm, which is 2% to 3% larger than that of pure g-C3N4.

[0040] This invention also provides the application of GO-coupled modified g-C3N4 photocatalyst in photocatalytic water splitting to produce hydrogen. The GO-coupled modified g-C3N4 photocatalyst is dispersed in an aqueous solution containing a sacrificial agent, a platinum source is added to perform photodeposition of platinum, and then the photocatalytic reaction is carried out under visible light irradiation and a protective atmosphere.

[0041] In this invention, the sacrificial agent is triethanolamine (TEOA), with a volume concentration of 10% in the aqueous solution; the platinum loading in the catalyst is 3 wt.%; the photodeposition of platinum is performed using ultrasound, with a power of 300 W and a duration of 30 min; the protective atmosphere is nitrogen, with nitrogen of ≥99.99% purity first introduced for 30 min to purge air, maintaining a nitrogen flow rate of 50 mL / min; then, a 300 W xenon lamp is used as the light source, equipped with a 420 nm cutoff filter (visible light irradiation), and the photoreaction is carried out at 25±2℃ and pH 7-8. The hydrogen production is detected every 1 h using a gas chromatograph, and the hydrogen evolution rate is calculated.

[0042] In this invention, the concentration of the GO-coupled modified g-C3N4 photocatalyst in aqueous solution is 0.5 mg / mL to ensure sufficient catalyst dispersion, and the TEOA concentration of 10% is adapted to the hole capture requirement, reducing the photogenerated electron-hole recombination rate to less than 1 / 3 of that of pure g-C3N4. If the amount of photocatalyst is <0.5 mg / mL (e.g., 0.4 mg / mL), there are insufficient active sites, and the hydrogen evolution rate drops to 900 μmol·g⁻¹. -1 ·h -1 ~1000μmol·g -1 ·h -1 (Decrease of 20%–25%); if the catalyst dosage is >0.5 mg / mL (e.g., 0.6 mg / mL), the catalyst will agglomerate, the light absorption efficiency will decrease, and the hydrogen evolution rate will drop to 1000 μmol·g⁻¹. -1 ·h -1 ~1100μmol·g -1 ·h -1 (8%–12% decrease); a 10% TEOA concentration is suitable for this dosage: excessive TEOA (e.g., 15%) will lead to increased solution viscosity and decreased water molecule diffusion rate; insufficient TEOA (e.g., 5%) will result in insufficient hole capture and a 40% increase in carrier recombination rate. It can directly utilize visible light (accounting for 44% of total solar irradiance) to drive hydrogen evolution, is compatible with industrial-grade photocatalytic reaction devices, and provides a low-cost catalyst solution for green hydrogen production.

[0043] This invention features a process free of heavy metals (Pt is used only in small amounts as a co-catalyst, and there is no leaching) and toxic solvents (only deionized water is used). The catalyst is biodegradable after disposal (g-C3N4 is a non-metallic material), meeting the requirements of "zero-pollution" production. It boasts strong energy adaptability: it can directly utilize visible light (accounting for 44% of total solar irradiance) to drive hydrogen evolution, requiring no additional electricity / heat energy, making it suitable for scenarios such as "solar photocatalytic hydrogen production stations," providing a low-cost catalyst solution for "green hydrogen" production. It also exhibits strong compatibility; the catalyst is compatible with existing industrial-grade photocatalytic reaction devices (such as flat-plate and batch photoreactors) without requiring equipment modification, reducing application costs for enterprises. This modification approach can be extended to "GO modification of other semiconductors (such as TiO2, CdS, etc.)," ​​reserving space for future patent layout; simultaneously, by adjusting the GO content, it can adapt to different lighting scenarios such as "low-concentration visible light (indoor light)" and "high-concentration visible light (desert areas)."

[0044] The following specific examples will provide further explanation.

[0045] Example 1 A method for preparing GO-coupled modified g-C3N4 photocatalyst, such as... Figure 1 As shown, it includes the following steps: S1. Using melamine with a purity greater than 99% as the sole precursor, place it in a covered alumina crucible with a gap of ≤2mm between the crucible lid and the crucible. Under an air atmosphere, place the crucible in a programmed temperature rise box furnace and heat it from room temperature to 550℃ at a heating rate of 5℃ / min. Calcinate it at 550℃ for 4 hours. After naturally cooling to room temperature, grind it with an agate mortar until the particle size is ≤75μm to obtain g-C3N4 powder with a layered stacked structure.

[0046] S2. Disperse g-C3N4 powder in deionized water at a solid-liquid ratio of 1g:50mL, sonicate for 2h using a digitally controlled ultrasonic instrument with a frequency of 40kHz and a power of 300W, and let stand for 30min under magnetic stirring at 200r / min until there is no obvious sedimentation to obtain g-C3N4 dispersion.

[0047] S3. Add GO powder to the above dispersion. The GO powder must meet the following requirements: purity ≥99%, thickness 1nm~5nm, flake diameter 3μm~8μm, D 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g; The mass ratio of GO to g-C3N4 was 0.1:100. The mixture was ultrasonically treated for 2 hours at 40 kHz and 300 W. After ultrasonic treatment, solid-liquid separation was performed. The mixture was filtered under a vacuum of -0.06 to -0.09 MPa using a PVDF microporous membrane with a pore size of 0.45 μm. The filter cake was collected, and the moisture content of the filter cake was controlled at 10%. The filter cake was placed in an electric heating drying oven with a temperature control accuracy of ±1℃ and dried at a constant temperature of 70±5℃ in an air atmosphere for 12 hours. The moisture content of the dried filter cake was ≤5%. The dried product was then ground to a particle size of ≤75 μm to obtain the GO-coupled modified g-C3N4 photocatalyst, named 0.1%GO-g-C3N4.

[0048] Example 2 A method for preparing GO-coupled modified g-C3N4 photocatalyst, such as... Figure 1 As shown, it includes the following steps: S1. Using melamine with a purity greater than 99% as the sole precursor, place it in a covered alumina crucible with a gap of ≤2mm between the crucible lid and the crucible. Under an air atmosphere, place the crucible in a programmed temperature rise box furnace and heat it from room temperature to 550℃ at a heating rate of 5℃ / min. Calcinate it at 550℃ for 4 hours. After naturally cooling to room temperature, grind it with an agate mortar until the particle size is ≤75μm to obtain g-C3N4 powder with a layered stacked structure.

[0049] S2. Disperse g-C3N4 powder in deionized water at a solid-liquid ratio of 1g:50mL, sonicate for 2h using a digitally controlled ultrasonic instrument with a frequency of 40kHz and a power of 300W, and let stand for 30min under magnetic stirring at 200r / min until there is no obvious sedimentation to obtain g-C3N4 dispersion.

[0050] S3. Add GO powder to the above dispersion. The GO powder must meet the following requirements: purity ≥99%, thickness 1nm~5nm, flake diameter 3μm~8μm, D 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g; The mass ratio of GO to g-C3N4 was 0.5:100. The mixture was ultrasonically treated for 2 hours at 40 kHz and 300 W. After ultrasonic treatment, solid-liquid separation was performed. The mixture was filtered under vacuum of -0.06 to -0.09 MPa using a polyvinylidene fluoride (PVDF) microporous membrane with a pore size of 0.45 μm. The filter cake was collected, and the moisture content of the filter cake was controlled at 15%. The filter cake was placed in an electric heating drying oven with a temperature control accuracy of ±1℃ and dried at a constant temperature of 70±5℃ in an air atmosphere for 12 hours. After drying, the moisture content of the filter cake was ≤5%. The dried product was then ground to a particle size of ≤75 μm to obtain the GO-coupled modified g-C3N4 photocatalyst, named 0.5%GO-g-C3N4.

[0051] Example 3 A method for preparing GO-coupled modified g-C3N4 photocatalyst, such as... Figure 1 As shown, it includes the following steps: S1. Using melamine with a purity greater than 99% as the sole precursor, place it in a covered alumina crucible with a gap of ≤2mm between the crucible lid and the crucible. Under an air atmosphere, place the crucible in a programmed temperature rise box furnace and heat it from room temperature to 550℃ at a heating rate of 5℃ / min. Calcinate it at 550℃ for 4 hours. After naturally cooling to room temperature, grind it with an agate mortar until the particle size is ≤75μm to obtain g-C3N4 powder with a layered stacked structure.

[0052] S2. Disperse g-C3N4 powder in deionized water at a solid-liquid ratio of 1g:50mL, sonicate for 2h using a digitally controlled ultrasonic instrument with a frequency of 40kHz and a power of 300W, and let stand for 30min under magnetic stirring at 200r / min until there is no obvious sedimentation to obtain g-C3N4 dispersion.

[0053] S3. Add GO powder to the above dispersion. The GO powder must meet the following requirements: purity ≥99%, thickness 1nm~5nm, flake diameter 3μm~8μm, D 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g; The mass ratio of GO to g-C3N4 was 1:100. The mixture was further ultrasonically treated at 40kHz and 300W for 2h. After ultrasonic treatment, solid-liquid separation was performed. The mixture was filtered under a vacuum of -0.06 to -0.09MPa using a PVDF microporous membrane with a pore size of 0.45μm. The filter cake was collected, and the moisture content of the filter cake was controlled at 15%. The filter cake was placed in an electric heating drying oven with a temperature control accuracy of ±1℃ and dried at a constant temperature of 70±5℃ in an air atmosphere for 12h. After drying, the moisture content of the filter cake was ≤5%. The dried product was then ground to a particle size of ≤75μm to obtain the GO-coupled modified g-C3N4 photocatalyst, named 1%GO-g-C3N4.

[0054] Example 4 A method for preparing GO-coupled modified g-C3N4 photocatalyst, such as... Figure 1 As shown, it includes the following steps: S1. Using melamine with a purity greater than 99% as the sole precursor, place it in a covered alumina crucible with a gap of ≤2mm between the crucible lid and the crucible. Under an air atmosphere, place the crucible in a programmed temperature rise box furnace and heat it from room temperature to 550℃ at a heating rate of 5℃ / min. Calcinate it at 550℃ for 4 hours. After naturally cooling to room temperature, grind it with an agate mortar until the particle size is ≤75μm to obtain g-C3N4 powder with a layered stacked structure.

[0055] S2. Disperse g-C3N4 powder in deionized water at a solid-liquid ratio of 1g:50mL, sonicate for 2h using a digitally controlled ultrasonic instrument with a frequency of 40kHz and a power of 300W, and let stand for 30min under magnetic stirring at 200r / min until there is no obvious sedimentation to obtain g-C3N4 dispersion.

[0056] S3. Add GO powder to the above dispersion. The GO powder must meet the following requirements: purity ≥99%, thickness 1nm~5nm, flake diameter 3μm~8μm, D 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g; The mass ratio of GO to g-C3N4 was 2:100. The mixture was further ultrasonically treated at 40kHz and 300W for 2h. After ultrasonic treatment, solid-liquid separation was performed. The mixture was filtered under a vacuum of -0.06 to -0.09MPa using a PVDF microporous membrane with a pore size of 0.45μm. The filter cake was collected, and the moisture content of the filter cake was controlled at 15%. The filter cake was placed in an electric heating drying oven with a temperature control accuracy of ±1℃ and dried at a constant temperature of 70±5℃ in an air atmosphere for 12h. After drying, the moisture content of the filter cake was ≤5%. The dried product was then ground to a particle size of ≤75μm to obtain the GO-coupled modified g-C3N4 photocatalyst, named 2%GO-g-C3N4.

[0057] Example 5 A method for preparing GO-coupled modified g-C3N4 photocatalyst, such as... Figure 1 As shown, it includes the following steps: S1. Using melamine with a purity greater than 99% as the sole precursor, place it in a covered alumina crucible with a gap of ≤2mm between the crucible lid and the crucible. Under an air atmosphere, place the crucible in a programmed temperature rise box furnace and heat it from room temperature to 550℃ at a heating rate of 5℃ / min. Calcinate it at 550℃ for 4 hours. After naturally cooling to room temperature, grind it with an agate mortar until the particle size is ≤75μm to obtain g-C3N4 powder with a layered stacked structure.

[0058] S2. Disperse g-C3N4 powder in deionized water at a solid-liquid ratio of 1g:50mL, sonicate for 2h using a digitally controlled ultrasonic instrument with a frequency of 40kHz and a power of 300W, and let stand for 30min under magnetic stirring at 200r / min until there is no obvious sedimentation to obtain g-C3N4 dispersion.

[0059] S3. Add GO powder to the above dispersion. The GO powder must meet the following requirements: purity ≥99%, thickness 1nm~5nm, flake diameter 3μm~8μm, D 50 <10μm, specific surface area is 45m² 2 / g~46m 2 / g; The mass ratio of GO to g-C3N4 was 4:100. The mixture was further ultrasonically treated at 40kHz and 300W for 2h. After ultrasonic treatment, solid-liquid separation was performed. The mixture was filtered under a vacuum of -0.06 to -0.09MPa using a PVDF microporous membrane with a pore size of 0.45μm. The filter cake was collected, and the moisture content of the filter cake was controlled at 15%. The filter cake was placed in an electric heating drying oven with a temperature control accuracy of ±1℃ and dried at a constant temperature of 70±5℃ in an air atmosphere for 12h. After drying, the moisture content of the filter cake was ≤5%. The dried product was then ground to a particle size of ≤75μm to obtain the GO-coupled modified g-C3N4 photocatalyst, named 4%GO-g-C3N4.

[0060] Comparative Example 1 A method for preparing a g-C3N4 photocatalyst includes the following steps: S1. Using melamine with a purity greater than 99% as the sole precursor, place it in a covered alumina crucible with a gap of ≤2mm between the crucible lid and the crucible. Under an air atmosphere, place the crucible in a programmed temperature rise box furnace and heat it from room temperature to 550℃ at a heating rate of 5℃ / min. Calcinate it at 550℃ for 4 hours and allow it to cool naturally to room temperature. Then grind it with an agate mortar until the particle size is ≤75μm to obtain g-C3N4 powder with a layered stacked structure, which is the g-C3N4 photocatalyst.

[0061] The structure and performance of the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 and the g-C3N4 photocatalyst prepared in Comparative Example 1 were analyzed, and the results are shown below.

[0062] Figure 2 The images show the microstructures of the GO-coupled modified g-C3N4 photocatalyst prepared in Example 4 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 2 In the image, (a) is a scanning electron microscope (SEM) image of GO, (b) is a scanning electron microscope (SEM) image of g-C3N4 photocatalyst, (c) is a scanning electron microscope (SEM) image of 2% GO-g-C3N4 photocatalyst, (d) is a transmission electron microscope (TEM) image of GO, (e) is a TEM image of g-C3N4 photocatalyst, and (c) is a TEM image of 2% GO-g-C3N4 photocatalyst. Figure 2 As shown, a layered structure of g-C3N4 was observed dispersed on the GO substrate, with a large number of pores (pore size 4nm~20nm).

[0063] Figure 3 The images show the XRD patterns of the g-C3N4 and GO-coupled modified g-C3N4 photocatalysts of this invention. Figure 3As shown, the characteristic peaks of g-C3N4 are retained (12.78° corresponds to the (100) crystal plane and 27.38° corresponds to the (002) crystal plane), and there are no new impurity peaks, proving that GO does not destroy the g-C3N4 structure. By calculating the height of the characteristic peaks, the intensity ratio of the characteristic peaks of the (100) crystal plane to the (002) crystal plane is 1:8~10.

[0064] Figure 4 This is the adsorption isotherm diagram of g-C3N4 and GO according to the present invention. Figure 4 In the diagram, (a) represents GO and (b) represents g-C3N4. Figure 5 This is the adsorption isotherm diagram of the GO-coupled modified g-C3N4 photocatalyst of this invention. Figure 5 In the above, (a) is a 0.1% GO-g-C3N4 photocatalyst, (b) is a 0.5% GO-g-C3N4 photocatalyst, (c) is a 1% GO-g-C3N4 photocatalyst, (d) is a 2% GO-g-C3N4 photocatalyst, and (e) is a 4% GO-g-C3N4 photocatalyst. The specific surface area of ​​the g-C3N4 was determined to be 10.30 m² using the BET method. 2 / g, the specific surface area of ​​0.1% GO-g-C3N4 photocatalyst is 10.55m². 2 / g, the specific surface area of ​​0.5% GO-g-C3N4 photocatalyst is 10.81m². 2 The specific surface area of ​​the 1% GO-g-C3N4 photocatalyst is 13.92 m² / g. 2 / g, the specific surface area of ​​2% GO-g-C3N4 photocatalyst is 15.32m². 2 / g, the specific surface area of ​​4% GO-g-C3N4 photocatalyst is 13.78m². 2 / g. When the GO loading is 2%, its specific surface area increases from 10.30 m² / g for pure g-C₃N₄. 2 / g increased to 15.32m 2 / g.

[0065] Figure 6 The visible light absorption diagrams of the GO-coupled modified g-C3N4 photocatalyst and the g-C3N4 photocatalyst of this invention are shown. Figure 7 This is a bandgap diagram of the GO-coupled modified g-C3N4 photocatalyst and the g-C3N4 photocatalyst of the present invention. Figure 7 In the diagram, (a) is the bandgap width curve, and (b) is the bandgap distribution map. Figure 6 and Figure 7As shown, the UV-Vis absorption edge of g-C3N4 is 453 nm, with a band gap of 2.58 eV. After GO modification, the absorption edge of the GO-g-C3N4 composite material exhibits a significant redshift, which may be due to defects introduced during the modification process, consistent with the results of transmission electron microscopy. This redshift in the visible light range promotes the generation of photogenerated electron-hole pairs, thereby improving photocatalytic performance. Using the Kubelka-Munk function, the band gap energy of various photocatalysts was calculated. With increasing GO concentration, the band gap energy of the GO-g-C3N4 composite material decreased sequentially to 2.58 eV, 2.55 eV, 2.55 eV, 2.54 eV, 2.51 eV, and 2.45 eV. This trend indicates that coupling GO into g-C3N4 alters the electronic structure of the composite material, expands the light absorption range, and thus improves photocatalytic efficiency.

[0066] Figure 8 The images show the FTIR spectra of the GO-coupled modified g-C3N4 photocatalyst and the g-C3N4 photocatalyst of this invention. Figure 8 In the image, (a) shows a g-C3N4 photocatalyst and GO, and (b) shows a GO-coupled modified g-C3N4 photocatalyst. Figure 8 As shown in (a), GO is at 3400cm -1 1720cm -1 1625cm -1 1625cm -1 and 1052cm -1 There are four main absorption peaks at 3400 cm⁻¹. -1 The peaks on the left and right belong to the bending vibration of the OH bond, while the peak at 1720 cm⁻¹... -1 The peak at 1625 cm⁻¹ corresponds to the stretching vibration of the C=O bond. -1 The peak at 1052 cm⁻¹ is related to the vibration of the C=C bond. -1 The peak at 806 cm⁻¹ is attributed to the stretching vibration of the CO bond. Furthermore, g-C₃N₄ shows a peak at 806 cm⁻¹. -1 The absorption peak at 1650 cm⁻¹ corresponds to the skeletal vibrations of the heptaazine ring. -1 ~1200cm -1 The broad absorption band between them belongs to the typical stretching vibration of the CN heterocycle, 1637 cm⁻¹. -1 The peak at 3400 cm⁻¹ is attributed to the stretching vibration of the C=N bond. -1 ~3000cm -1 The peaks within this range are caused by the stretching vibrations of the -NH2 and -NH groups. For example... Figure 8As shown in Figure (b), the FTIR spectra of GO-g-C3N4 composites with different GO contents retain the characteristic peaks of g-C3N4. However, due to the low GO content, no obvious peaks are observed in the GO-g-C3N4 composites. Notably, the characteristic peaks of g-C3N4 in the GO-g-C3N4 spectrum shift with increasing GO content. For example, in the spectrum of 4% GO-g-C3N4, the heptaazine ring skeletal vibration peak shifts to 804 cm⁻¹. -1 Furthermore, the absorption peak representing the CN bond shows a red shift, as do the peaks corresponding to the -NH2 and -NH groups. Simultaneously, the intensity of some characteristic peaks gradually decreases with increasing GO content. These changes indicate that the interaction between GO and g-C3N4 in the GO-g-C3N4 composite material is not a simple physical blending, but rather a more complex interaction mechanism.

[0067] Figure 9 XPS spectra of the GO-coupled modified g-C3N4 photocatalyst prepared in Example 4 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 9 In the image, (a) is the full spectrum, (b) is the C 1s spectrum of GO, (c) is the O 1s spectrum of GO, (d) is the C 1s spectrum of g-C3N4, (e) is the N 1s spectrum of g-C3N4, (f) is the O 1s spectrum of g-C3N4, (g) is the C 1s spectrum of 2% GO-g-C3N4 photocatalyst, (h) is the N 1s spectrum of 2% GO-g-C3N4 photocatalyst, and (i) is the O 1s spectrum of 2% GO-g-C3N4 photocatalyst. Figure 9 As shown in (a), the XPS total spectrum of the 2% GO-g-C3N4 catalyst contains characteristic peaks of C1s, N1s, and O1s, which are attributed to the presence of GO and g-C3N4. This result confirms the successful recombination of GO and g-C3N4; Figure 9 As shown in (b) and (c), the GO sample exhibits four deconvolution peaks at 284.8 eV, 286.88 eV, 287.9 ​​eV, and 288.6 eV, indicating the presence of four different types of carbon bonds in the GO structure. The peak at 284.8 eV corresponds to C-C and C=C bonds, confirming the typical structure of GO. The peaks at 286.88 eV and 287.9 ​​eV are related to CO and C=O bonds, respectively. The peak at 288.6 eV is related to C=O(OH) bonds. The 1s XPS spectrum shows three peaks at 531.13 eV, 532.49 eV, and 533.15 eV, corresponding to the COO-, C=O, and OH functional groups, respectively. Figure 9As shown in (d) to (f), the XPS spectra of the C 1s of g-C3N4, at binding energies of 284.8 cV, 286.17 eV, 288.09 eV, and 293.4 eV, deconvolve to four distinct peaks. These peaks are associated with CC / C=C, C-NH, NC=N, and π-π satellite peaks, respectively. In the N 1s XPS spectra, four characteristic peaks are observed at 398.47 eV, 400.17 eV, 401.15 eV, and 403.96 eV, corresponding to C=NCC, N-C3, NH, and charge localization effects within the heterocycle. Furthermore, the O 1s XPS spectra show two peaks at 532.13 eV and 533.48 eV, corresponding to C=O / CO and OH, respectively. The presence of oxygen in g-C3N4 may be due to the adsorption of water molecules from air C. Figure 9 As shown in (g) to (i), the XPS spectra of the 2% GO-g-C3N4 composite are very similar to those of g-C3N4. However, the peaks of 2% GO-g-C3N4 show a significant shift towards higher binding energies, indicating that the chemical interaction between GO and g-C3N4 leads to a higher oxidation state. Furthermore, the characteristic peak at 286.73 eV in the C 1s spectrum of 2% GO-g-C3N4 increases significantly, while the characteristic peak at 400.28 eV in the N 1s spectrum decreases significantly. These results suggest that the heptaazine ring structure in g-C3N4 may be disrupted during GO modification. Additionally, the peak area ratio (Acoc-o / AoH) of the O 1s spectrum of the 2% GO-g-C3N4 composite is significantly larger than that of g-C3N4, indicating a chemical bond between GO and g-C3N4. The XPS analysis results are consistent with those of TEM, XRD, and FTIR.

[0068] The GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 and the g-C3N4 photocatalyst prepared in Comparative Example 1 were used for photocatalytic hydrogen evolution, including the following steps: At a solid-liquid ratio of 0.5 mg / mL, the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 and the g-C3N4 photocatalyst prepared in Comparative Example 1 were added to an aqueous solution containing 10% triethanolamine (TEOA), and H2PtCl6・6H2O was added to make the Pt loading 3% of the catalyst mass. The mixture was ultrasonicated at 300W power for 30 min to make the catalyst uniformly dispersed and complete the Pt photodeposition to form a dispersion.

[0069] The dispersion was placed in a photocatalytic activity evaluation system (model: CEL-PAEM-D8), and nitrogen gas with a purity ≥99.99% was introduced for 30 min to purge the air from the device, maintaining a nitrogen flow rate of 50 mL / min. A 300W xenon lamp was used as the light source, equipped with a 420nm cutoff filter (visible light irradiation), and the photocatalytic reaction was carried out at 25±2℃ and pH 7-8. The hydrogen production was detected every 1 h using a gas chromatograph (model: GC-7920), and the hydrogen evolution rate was calculated.

[0070] Figure 10 The figures show the hydrogen evolution performance of the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 10 (a) is the hydrogen evolution rate curve, (b) is the hydrogen evolution rate curve, and (c) is the cycle diagram of the 2% GO-g-C3N4 photocatalyst. Figure 10 As shown, the hydrogen evolution rate of the comparative example 1 g-C3N4 photocatalyst within 5 h was 2084.1 μmol·g. -1 The average hydrogen evolution rate was 416.8 μmol·g. -1 ·h -1 Example 1: 0.1% GO-g-C3N4 photocatalyst, hydrogen evolution rate within 5 hours was 3049.5 μmol·g. -1 The average hydrogen evolution rate was 609.9 μmol·g. -1 ·h -1 Example 2: 0.5% GO-g-C3N4 photocatalyst, hydrogen evolution rate within 5 hours was 3500.7 µmol·g. -1 The average hydrogen evolution rate was 700.1 μmol·g. -1 ·h -1 Example 3: 1% GO-g-C3N4 photocatalyst, hydrogen evolution rate within 5 hours was 3942.1 µmol·g. -1 The average hydrogen evolution rate was 788.4 μmol·g. -1 ·h -1 Example 4: 2% GO-g-C3N4 photocatalyst, hydrogen evolution rate within 5 hours was 6145.4 μmol·g. -1 The average hydrogen evolution rate was 1229.1 μmol·g. -1 ·h -1 (2.95 times that of pure g-C3N4); Example 5: 4% GO-g-C3N4 photocatalyst, hydrogen evolution rate within 5 hours: 5268.0 μmol·g -1 The average hydrogen evolution rate was 1053.6 μmol·g. -1 ·h -1This indicates that excessive GO content can induce aggregation, thereby reducing performance. After four cycles (20 h) of cycling, the hydrogen evolution rate of the 2% GO-g-C3N4 photocatalyst was 1125.1 μmol·g⁻¹. -1 ·h -1 Maintain 91.5% of the initial value.

[0071] Figure 11 The electrochemical impedance spectroscopy (EIS) spectra of the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 of this invention and the g-C3N4 photocatalysts prepared in Comparative Example 1 are shown. Figure 12 The transient photocurrent response diagrams are for the GO-coupled modified g-C3N4 photocatalysts prepared in Examples 1 to 5 of this invention and the g-C3N4 photocatalyst prepared in Comparative Example 1. Figure 11 and Figure 12 As shown, the 2% GO-g-C3N4 photocatalyst has the lowest EIS impedance (approximately 260Ω), the highest photocurrent density (0.15mA / cm²), and the best carrier separation efficiency.

[0072] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A method for preparing a GO-coupled modified g-C 3N 4 photocatalyst, characterized in that, Includes the following steps: The layered stacked structure of g-C3N4 was dispersed in a solvent and subjected to a first ultrasonic exfoliation to obtain a g-C3N4 dispersion. Graphene oxide was added to the g-C3N4 dispersion and subjected to a second ultrasonic exfoliation to allow the graphene oxide and g-C3N4 to undergo π-π stacking and hydrogen bonding. After solid-liquid separation, the mixture was dried to form a composite structure, which was then ground to a particle size ≤75μm, resulting in a composite structure containing pore defects with a pore size of 4nm to 20nm, thus obtaining a GO-coupled modified g-C3N4 photocatalyst.

2. The method for preparing a GO coupling modified g-C3N4 photocatalyst according to claim 1, characterized in that, The mass ratio of graphene oxide to g-C3N4 is 0.1 to 4:

100.

3. The method for preparing GO coupling modified g-C3N4 photocatalyst according to claim 1, characterized in that, The specific surface area of g-C3N4 is 10.0 m2 / g 2 / g~10.5 m2 / g 2 The ratio of the characteristic peak intensity of (100) crystal face to (002) crystal face is 1:8~10.

4. The preparation method of GO-coupled modified g-C3N4 photocatalyst according to claim 1, characterized in that, The thickness of the graphene oxide is 1 nm to 5 nm, the flake diameter is 3 μm to 8 μm, and D 50 <10 μm, and the specific surface area is 45 m 2 / g to 46 m 2 / g.

5. The preparation method of GO-coupled modified g-C3N4 photocatalyst according to claim 1, characterized in that, The frequency of the first and second ultrasonic ablation procedures was 40 kHz, the power was 300 W, and the duration was 1 to 3 hours.

6. The preparation method of the GO-coupled modified g-C3N4 photocatalyst according to claim 1, characterized in that, The preparation method of g-C3N4 with a layered stacked structure includes the following steps: Melamine was used as raw material and calcined at 540℃~560℃ in air atmosphere. After calcination, the material was ground to a particle size ≤75μm to obtain g-C3N4 with a layered stacked structure. The heating rate during calcination was 4℃ / min~6℃ / min and the calcination time was 3.5h~4.5h.

7. A GO-coupled modified g-C3N4 photocatalyst, characterized in that, It is prepared using any one of the preparation methods of claims 1 to 6.

8. The GO-coupled modified g-C3N4 photocatalyst according to claim 7, characterized in that, The photocatalyst is a g-C3N4 sheet layer as a carrier, and graphene oxide is loaded, the specific surface area of the photocatalyst is 10.55m 2 / g~15.52m 2 / g, the interlayer spacing is 0.320nm~0.322nm, and the band gap is 2.45eV~2.58eV.

9. The application of the GO-coupled modified g-C3N4 photocatalyst according to claim 7 or claim 8 in photocatalytic water splitting for hydrogen production, characterized in that, GO-coupled modified g-C3N4 photocatalyst was dispersed in an aqueous solution containing a sacrificial agent, and a platinum source was added to perform photodeposition of platinum. Subsequently, the photocatalytic reaction was carried out under visible light irradiation and a protective atmosphere.

10. The application according to claim 9, characterized in that, The sacrificial agent is triethanolamine, and the volume concentration of the sacrificial agent in the aqueous solution is 10%; the loading of platinum in the catalyst is 3.0 wt%.

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