A double-defect Ni / NiO x @C catalyst and its preparation method and application in photothermal-assisted photocatalytic hydrogen production

Abstract

The present invention discloses a double-defect Ni / NiO x @C catalyst and its preparation method and application in photothermal assisted photocatalytic hydrogen production belong to the field of photocatalytic materials. The present invention uses nickel source, citric acid, anhydrous ethanol and water as raw materials, and synthesizes Ni / NiO with Ni and O double defects by sol-gel method combined with carbon thermal in situ synchronous co-reduction process. x The method is simple to operate, has a short reaction time, and high synthesis efficiency. Using these heterogeneous nanoparticles as a co-catalyst and g-C3N4 as a primary catalyst, a composite photocatalyst can significantly improve the efficiency of photocatalytic water splitting to produce hydrogen through the synergistic effects of photothermal effects and hindered Lewis acid-base sites.

Description

Technical Field

[0001] The present invention belongs to the field of photocatalytic materials, and specifically relates to a double-defect Ni / NiO x @C catalyst, its preparation method and application in photothermal-assisted photocatalytic hydrogen production. Background Art

[0002] As the negative effects of fossil fuel-based energy production continue to intensify, semiconductor photocatalytic water splitting for hydrogen production is a potential solution to meet future clean energy conversion needs. However, single-component semiconductor photocatalysts exhibit low photocatalytic activity due to ultrafast photogenerated carrier recombination and sluggish interfacial dynamics. Coupling cocatalysts is an ingenious and successful strategy to accelerate carrier migration and interfacial reactions. However, the high cost and scarce reserves of highly active noble metal cocatalysts severely limit their practical application in photocatalysis. Recently, multi-component heterogeneous cocatalysts, such as binary non-noble metal alloys, metal-carbon, and metal-semiconductor catalysts, have made significant progress in improving the performance of photocatalytic water splitting for hydrogen production due to their careful design and strong synergistic effects. However, methods to effectively integrate the structure-activity relationships of multiple components and to deeply understand the active sites of heterogeneous catalysts are still extremely lacking in current research. Therefore, it is of great significance to carefully design multi-component heterogeneous cocatalysts with high catalytic activity and to explore the interaction mechanisms between the components.

[0003] In the process of semiconductor photocatalytic hydrogen evolution, effectively reducing the recombination of photogenerated carriers and accelerating the interfacial catalytic reaction are crucial to the performance of photocatalytic hydrogen evolution. At the same time, adjusting the electronic state and atomic structure of the surface interface of the co-catalyst is also closely related to the performance of the main photocatalyst. In the field of heterogeneous catalysis, constructing frustrated Lewis pairs (FLPs) is a simple and effective means of surface modification. FLPs retain the basic interaction between Lewis acid and Lewis base through steric hindrance or electronic effects, thereby triggering the ability of FLPs to activate small molecules. However, it is not easy to break the classic Lewis acid-base bond to construct FLPs. Fortunately, solid "rigid" frameworks with various structural defects will provide opportunities for the design and synthesis of semi-solid and solid FLPs-type catalysts. Summary of the Invention

[0004] In view of the shortcomings and deficiencies of the above prior art, the primary purpose of the present invention is to provide a double-defect Ni / NiO with hindered Lewis acid-base pair and photothermal induced effect. x @C catalyst.

[0005] Another object of the present invention is to provide the above double defect Ni / NiO x @C Preparation method of catalyst.

[0006] Another object of the present invention is to provide a composite photocatalyst prepared from Ni / NiOx@C co-catalyst having a hindered Lewis acid-base pair.

[0007] Another object of the present invention is to provide an application of the composite photocatalyst in photothermal-assisted photocatalytic water decomposition to produce hydrogen.

[0008] The purpose of the present invention is achieved through the following technical solutions.

[0009] A double-defect Ni / NiO x @C catalyst, the double-defect Ni / NiO x @C catalyst is Ni / NiO with core-shell structure x @C, which has Ni and O double vacancy defects, and effectively constructs active sites with hindered Lewis acid-base pairs under the spatial confinement of the graphene coating layer.

[0010] Preferably, the double defect Ni / NiO x The particle size of @C catalyst is 5 to 10 nm.

[0011] Double defect Ni / NiO of the present invention x @CThe size of the catalyst can be controlled by adjusting the amount of citric acid.

[0012] Double defect Ni / NiO of the present invention x Ni and NiO in @C catalyst x The composition ratio can be controlled by adjusting the calcination temperature, calcination time and the amount of citric acid added.

[0013] The double defect Ni / NiO x The deep energy level defects of the @C catalyst can effectively generate non-radiative photogenerated carrier recombination under photoexcitation, inducing the photothermal effect of the catalyst and reducing the reaction activation energy required for photocatalytic water decomposition to produce hydrogen.

[0014] The above-mentioned double-defect Ni / NiO x The preparation method of @C catalyst comprises the following steps:

[0015] (1) fully mixing and dissolving the nickel source, citric acid, anhydrous ethanol and water and then drying to obtain a precursor gel;

[0016] (2) annealing the precursor gel in an inert atmosphere to obtain a double-defect Ni / NiO x @C catalyst.

[0017] Preferably, the annealing temperature is 300° C.-450° C., and the annealing time is 4-10 hours.

[0018] Preferably, the annealing temperature is 400° C. and the annealing time is 8 hours.

[0019] Preferably, the heating rate of the annealing is 3°C / min.

[0020] Preferably, the nickel source is nickel acetate.

[0021] Preferably, the water is deionized water.

[0022] Preferably, the mass ratio of the nickel source to citric acid is 3-6:10, more preferably 2:5.

[0023] Preferably, the gelling condition is to dry the precursor gel in a forced air oven at 80° C. for 3 h.

[0024] Preferably, the inert atmosphere is high-purity Ar gas.

[0025] A composite photocatalyst comprising a main catalyst and a co-catalyst, wherein the co-catalyst is the double-defect Ni / NiO x @C catalyst.

[0026] Preferably, the double defect Ni / NiO x The added amount of @C catalyst accounts for 1% to 9% of the total mass of the composite photocatalyst, and more preferably 5%.

[0027] Preferably, the main catalyst is g-C3N4.

[0028] The composite photocatalyst described above is prepared by the following method: a double-defect Ni / NiO having a hindered Lewis acid-base pair is prepared. x The Ni / NiO composite material was obtained by mixing the @C catalyst and g-C3N4 in a certain proportion, ultrasonically self-assembling, freeze-drying, and mechanically grinding for 1 h. x @C / g-C3N4(NOCC).

[0029] Use of a composite photocatalyst as described in any one of the above in photocatalytic water decomposition to produce hydrogen.

[0030] Preferably, the sacrificial agent used in the application is a 10% triethanolamine aqueous solution.

[0031] This invention synthesizes heterogeneous nanoparticles with Ni and O dual defects using a sol-gel method combined with a carbon-thermal in-situ simultaneous co-reduction process. Composite photocatalysts prepared using these heterogeneous nanoparticles can significantly improve the efficiency of photocatalytic hydrogen production through the synergistic effects of the photothermal effect and hindered Lewis acid-base sites.

[0032] The present invention utilizes the confinement effect of the graphene coating layer to construct a ternary hybrid photocatalytic hydrogen evolution co-catalyst with FLPs, which includes graphene, metal and metal oxide. Experimental and theoretical studies have shown that the spatial Lewis acid-base sites constructed by the confinement of Ni and O vacancies effectively tune the interface barrier, thereby reducing the H-OH bond dissociation energy barrier and H * Adsorption and desorption Gibbs free energy. Kelvin probe test confirmed that Ni / NiO has defect states. x The @C cocatalyst can effectively induce photogenerated charge separation and promote interfacial charge rearrangement. In addition, the regional photothermal effect found in temperature-dependent fluorescence spectroscopy and infrared thermal imaging tests gave the composite photocatalyst a lower photogenerated carrier recombination rate and lower apparent activation energy, which is very beneficial for accelerating surface reaction kinetics. In actual hydrogen production performance tests, the best hydrogen production performance reached 10.7 mmol g -1 h -1 , which is 1.75 times that of 1wt% Pt as co-catalyst, Ni / NiO x The @C co-catalyst exhibits efficient hydrogen evolution activity and high photon utilization efficiency.

[0033] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0034] (1) The present invention uses easily available and highly commercialized nickel acetate, citric acid, and anhydrous ethanol as raw materials to synthesize Ni / NiO with a hindered Lewis acid-base pair by a sol-gel method combined with an in-situ carbothermal reduction process. x @C photothermal catalyst. Simple operation, short reaction time and high synthesis efficiency. x @C nanoparticles have core-shell structure and heterogeneous structure. The product is high in purity and small in particle size. The diameter of the nanoparticles is between 5 and 10 nm, the size distribution is very uniform, and it has a large specific surface area.

[0035] (2) Ni / NiO prepared by the present invention x @C nanoparticles have a core-shell structure and are covered with a carbon layer of appropriate thickness. They are not easily oxidized and can be stored for a long time, which is conducive to industrial-scale production.

[0036] (3) Ni / NiO prepared by the present invention x The spatial Lewis acid-base sites of @C nanoparticles, which are confined by Ni and O vacancies, effectively tune the interface barrier, thereby reducing the H-OH bond dissociation barrier and H * Gibbs free energy of adsorption and desorption.

[0037] (4) Ni / NiO prepared by the present invention x @C nanoparticles have deep energy level traps with defect states that can effectively induce photogenerated charge separation and promote interfacial charge rearrangement.

[0038] (5) Ni / NiO prepared by the present invention x @C nanoparticles can effectively induce photothermal effects, making the composite photocatalyst have a lower photogenerated carrier recombination rate and lower apparent activation energy, which is very beneficial for accelerating surface reaction kinetics.

[0039] (6) Ni / NiO prepared by the present invention x @C nanoparticles, in actual hydrogen production performance tests, the best hydrogen production performance reached 10.7mmol g -1 h -1 , which is 1.75 times that of loading 1wt% precious metal Pt as a co-catalyst. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 Ni / NiO obtained at different temperatures in Examples 1 to 4 of the present invention x @C SEM image of nanoparticles.

[0041] Figure 2 Ni / NiO obtained at different temperatures in Examples 1 to 4 of the present invention x @C XRD pattern of nanoparticles.

[0042] Figure 3 Example 3 is Ni / NiO x @C TEM image of nanoparticles.

[0043] Figure 4 Ni / NiO obtained at different temperatures in Examples 1 to 4 x @C XPS and ESR patterns of nanoparticles.

[0044] Figure 5 The composite material Ni / NiO obtained in Examples 5 to 9 x XRD diffraction pattern of @C / g-C3N4.

[0045] Figure 6 The composite material Ni / NiO obtained in Example 7 x TEM image of @C / g-C3N4.

[0046] Figure 7 Ni / NiO at different temperatures obtained in Example 13 x Hydrogen production rate diagram of the composite photocatalyst coupled with @C co-catalyst and g-C3N4.

[0047] Figure 8 This is a diagram of the hydrogen production rate of Pt / g-C3N4 photocatalysts with different Pt loading amounts obtained in Example 14.

[0048] Figure 9These are the photocatalytic hydrogen production rate diagrams of g-C3N4, OCC300, NOCC350, NOCC400, and NCC450 photocatalysts obtained in Examples 15-18 at 15°C, 25°C, 35°C, and 45°C, respectively.

[0049] Figure 10 C, Ni / NiO obtained in Example 19 x @C、g-C3N4、Ni / NiO x Infrared thermal imaging image of @C / g-C3N4.

[0050] Figure 11 g-C3N4 and Ni / NiO obtained in Example 19 x Infrared thermal imaging images of the @C / g-C3N4 reaction system before and after the reaction.

[0051] Figure 12 This is a fitting diagram of the activation energy of the photocatalytic reaction of the composite of g-C3N4 and co-catalysts at different temperatures obtained in Examples 15-18. DETAILED DESCRIPTION

[0052] The present invention will be described in further detail below with reference to the embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0053] Example 1 Preparation of co-catalyst

[0054] (1) 0.4 g nickel acetate, 1 g citric acid, 1 ml anhydrous ethanol, and 2.5 ml deionized water were fully dissolved in a porcelain boat, and then placed in a forced air drying oven at 80 °C for 3 h to obtain a precursor gel. Finally, the precursor gel was placed in a tube furnace and heated to 300 °C in an Ar atmosphere for 8 h at a heating rate of 3 °C / min and an Ar gas flow rate of 20 mL / min to obtain a brown powder, which was labeled as OC-300. Figure 1 As shown. Figure 2 It can be seen that the brown powder product obtained is high-purity NiO x @C nanoparticles. Figure 4 XPS and ESR tests show that the nanoparticles have Ni and O double vacancies. The detailed vacancy content is shown in Table 1.

[0055] Table 1

[0056]

[0057] spins is the total number of spins, M is the molar concentration, spins 3 is the concentration, the unit is mm 3

[0058] Example 2 Preparation of co-catalyst

[0059] (1) 0.4 g nickel acetate, 1 g citric acid, 1 ml anhydrous ethanol, and 2.5 ml deionized water were fully dissolved in a porcelain boat, and then placed in a forced air drying oven at 80 ° C for 3 h to obtain a precursor gel. Finally, it was placed in a tube furnace and heated to 350 ° C in an Ar atmosphere for 8 h. The heating rate was 3 ° C / min and the Ar gas flow rate was 20 mL / min to obtain a black powder, which was marked as NOC-350. Figure 1 As shown. Figure 2 It can be seen that the black powder product obtained is high-purity Ni / NiO x @C nanoparticles. Figure 4 XPS and ESR tests show that the nanoparticles have Ni and O double vacancies. The detailed vacancy content is shown in Table 1.

[0060] Example 3 Preparation of co-catalyst

[0061] (1) 0.4 g nickel acetate, 1 g citric acid, 1 ml anhydrous ethanol, and 2.5 ml deionized water were fully dissolved in a porcelain boat, and then placed in a forced air drying oven at 80 ° C for 3 h to obtain a precursor gel. Finally, it was placed in a tube furnace and heated to 400 ° C in an Ar atmosphere for 8 h. The heating rate was 3 ° C / min and the Ar gas flow rate was 20 mL / min to obtain a black powder, which was marked as NOC-400. Figure 1 As shown. Figure 2 It can be seen that the black powder product obtained is high-purity Ni / NiO x @C nanoparticles. Figure 3 The size of the nanoparticles is shown to be 5 to 10 nm. Figure 4 XPS and ESR tests show that the nanoparticles have Ni and O double vacancies. The detailed vacancy content is shown in Table 1.

[0062] Example 4 Preparation of co-catalyst

[0063] (1) 0.4 g nickel acetate, 1 g citric acid, 1 ml anhydrous ethanol, and 2.5 ml deionized water were fully dissolved in a porcelain boat, and then placed in a forced air drying oven at 80 ° C for 3 h to obtain a precursor gel. Finally, it was placed in a tube furnace and heated to 450 ° C in an Ar atmosphere for 8 hours at a heating rate of 3 ° C / min and an Ar gas flow rate of 20 mL / min to obtain a black powder, which was labeled as NC-450. Figure 1 It can be seen that the obtained black powder product is high-purity Ni@C nanoparticles. Figure 4 XPS and ESR tests show that the nanoparticles have Ni and O double vacancies. The detailed vacancy content is shown in Table 1.

[0064] Example 5 Preparation of composite catalyst

[0065] (1) Ni / NiO obtained in Example 3 x@C nanoparticles and g-C3N4 were mixed in a mass ratio of 1:99, ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NOCC1). Figure 5 The XRD pattern of the composite photocatalyst is shown, and further observation by transmission electron microscopy shows that Ni / NiO x @C nanoparticles and g-C3N4 are very evenly coupled together.

[0066] Example 6 Preparation of composite catalyst

[0067] (1) Ni / NiO obtained in Example 3 x @C nanoparticles and g-C3N4 were mixed in a mass ratio of 3:97, and then ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NOCC3). Figure 5 The XRD pattern of the composite photocatalyst is shown, and further observation by transmission electron microscopy shows that Ni / NiO x @C nanoparticles and g-C3N4 are very evenly coupled together.

[0068] Example 7 Preparation of composite catalyst

[0069] (1) Ni / NiO obtained in Example 3 x @C nanoparticles and g-C3N4 were mixed in a mass ratio of 5:95, ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NOCC5 or NOCC400). Figure 5 shows the XRD pattern of the composite photocatalyst, Figure 6 Further observation by transmission electron microscopy showed that Ni / NiO x @C nanoparticles and g-C3N4 are very evenly coupled together.

[0070] Example 8 Preparation of composite catalyst

[0071] (1) Ni / NiO obtained in Example 3 x @C nanoparticles and g-C3N4 were mixed in a mass ratio of 7:93, and then ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NOCC7). Figure 5 The XRD pattern of the composite photocatalyst is shown, and further observation by transmission electron microscopy shows that Ni / NiO x @C nanoparticles and g-C3N4 are very evenly coupled together.

[0072] Example 9 Preparation of composite catalyst

[0073] (1) Ni / NiO obtained in Example 3 x@C nanoparticles and g-C3N4 were mixed in a mass ratio of 9:91, ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NOCC9). Figure 5 The XRD pattern of the composite photocatalyst is shown, and further observation by transmission electron microscopy shows that Ni / NiO x @C nanoparticles and g-C3N4 are very evenly coupled together.

[0074] Example 10 Preparation of composite catalyst

[0075] (1) Ni / NiO obtained in Example 1 x @C nanoparticles and g-C3N4 were mixed in a mass ratio of 5:95, and then ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as OCC300).

[0076] Example 11 Preparation of composite catalyst

[0077] (1) Ni / NiO obtained in Example 2 x @C nanoparticles and g-C3N4 were mixed in a mass ratio of 5:95, and then ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NOCC350).

[0078] Example 12 Preparation of composite catalyst

[0079] (1) Ni / NiO obtained in Example 4 x @C nanoparticles and g-C3N4 were mixed in a mass ratio of 5:95, and then ultrasonically self-assembled, freeze-dried, and ground for 1 hour to obtain a composite material (denoted as NCC450).

[0080] Example 13 Photocatalytic Performance Test

[0081] In a standard photocatalytic hydrogen production experiment, 10 mg of the composite photocatalyst of Example 7 was dispersed in a 10% by volume aqueous solution of triethanolamine (TEOA), and 100 mL of the solution was transferred to a sealed magnetic top irradiation reactor made of quartz. A 300 W xenon lamp (127 mW cm -2 ) as the light source, and simulate sunlight through an AM1.5 filter (lamp distance is 15 cm). Before illumination, nitrogen bubbles were injected into the reactor for more than 30 minutes to form an anaerobic atmosphere. After the reaction started, 400 μL of gas was collected from the reactor and the efficiency of photocatalytic H2 was detected using gas chromatography (GC-7900). Figure 7 It can be seen that Ni / NiO prepared at 400℃ x @C has the best photocatalytic activity, Ni / NiO x The hydrogen production rate of @C / g-C3N4 composite photocatalyst is 10.7 mmol g -1h -1 , which is 1.75 times that of loading 1wt% Pt as a co-catalyst.

[0082] Example 14 Photocatalytic performance test of comparative samples

[0083] A photoreduction method was used, in which 1 wt.% Pt in H2PtCl6·6H2O was added to a bare g-C3N4 suspension and stirred under 300W white light irradiation for 1 hour. The solid obtained by centrifugation was dried to obtain PtC samples with a mass ratio of Pt to g-C3N4 of 0.25 wt.%, 0.5 wt.%, 1 wt.%, 2 wt.%, and 3 wt.%. The resulting composite samples were named PtC-X (X = 0.25, 0.5, 1, 2, and 3). Then, in a standard photocatalytic hydrogen production experiment, 10 mg of the composite PtC-X photocatalyst was dispersed in a 10 vol.% triethanolamine (TEOA) aqueous solution, and 100 mL of the solution was transferred to a sealed magnetic top irradiation reactor made of quartz. A 300W xenon lamp (127 mW cm -2 ) as the light source, and simulate sunlight through an AM1.5 filter (lamp distance is 15 cm). Before illumination, nitrogen bubbles were injected into the reactor for more than 30 minutes to form an anaerobic atmosphere. After the reaction started, 400 μL of gas was collected from the reactor and the efficiency of photocatalytic H2 was detected using gas chromatography (GC-7900). Figure 8 It can be seen that 1wt.% Pt / g-C3N4 photocatalyst has the best photocatalytic activity and the optimal hydrogen production rate is 6.1mmol g -1 h -1 , but still lower than Ni / NiO x Hydrogen production rate of @C / g-C3N4.

[0084] Example 15 Temperature-variable photocatalytic performance test

[0085] In a standard photocatalytic hydrogen production experiment, 10 mg of the composite photocatalyst of Example 10 was dispersed in a 10% by volume triethanolamine (TEOA) aqueous solution, and 100 mL of the solution was transferred to a sealed magnetic top irradiation reactor made of quartz. A 300 W xenon lamp (127 mW cm -2 ) was used as the light source, and sunlight was simulated through an AM1.5 filter (lamp distance was 15 cm). Before illumination, nitrogen bubbles were injected into the reactor for more than 30 minutes to form an anaerobic atmosphere. Hydrogen evolution was catalyzed at 15°C, 25°C, 35°C, and 45°C. After the reaction started, 400 μL of gas was collected from the reactor and the efficiency of photocatalytic H2 was detected using gas chromatography (GC-7900). The hydrogen production performance at different temperatures is shown in Figure 2. Figure 9 shown.

[0086] Example 16 Temperature-variable photocatalytic performance test

[0087] In a standard photocatalytic hydrogen production experiment, 10 mg of the composite photocatalyst of Example 11 was dispersed in a 10% by volume triethanolamine (TEOA) aqueous solution, and 100 mL of the solution was transferred to a sealed magnetic top irradiation reactor made of quartz. A 300 W xenon lamp (127 mW cm -2 ) was used as the light source, and sunlight was simulated through an AM1.5 filter (lamp distance was 15 cm). Before illumination, nitrogen bubbles were injected into the reactor for more than 30 minutes to form an anaerobic atmosphere. Hydrogen evolution was catalyzed at 15°C, 25°C, 35°C, and 45°C. After the reaction started, 400 μL of gas was collected from the reactor and the efficiency of photocatalytic H2 was detected using gas chromatography (GC-7900). The hydrogen production performance at different temperatures is shown in Figure 2. Figure 9 shown.

[0088] Example 17 Photocatalytic Performance Test

[0089] In a standard photocatalytic hydrogen production experiment, 10 mg of the composite photocatalyst of Example 7 was dispersed in a 10% by volume aqueous solution of triethanolamine (TEOA), and 100 mL of the solution was transferred to a sealed magnetic top irradiation reactor made of quartz. A 300 W xenon lamp (127 mW cm -2 ) was used as the light source, and sunlight was simulated through an AM1.5 filter (lamp distance was 15 cm). Before illumination, nitrogen bubbles were injected into the reactor for more than 30 minutes to form an anaerobic atmosphere. Hydrogen evolution was catalyzed at 15°C, 25°C, 35°C, and 45°C. After the reaction started, 400 μL of gas was collected from the reactor and the efficiency of photocatalytic H2 was detected using gas chromatography (GC-7900). The hydrogen production performance at different temperatures is shown in Figure 2. Figure 9 shown.

[0090] Example 18 Temperature-variable photocatalytic performance test

[0091] In a standard photocatalytic hydrogen production experiment, 10 mg of the composite photocatalyst of Example 12 was dispersed in a 10% by volume triethanolamine (TEOA) aqueous solution, and 100 mL of the solution was transferred to a sealed magnetic top irradiation reactor made of quartz. A 300 W xenon lamp (127 mW cm -2 ) was used as the light source, and sunlight was simulated through an AM1.5 filter (lamp distance was 15 cm). Before illumination, nitrogen bubbles were injected into the reactor for more than 30 minutes to form an anaerobic atmosphere. Hydrogen evolution was catalyzed at 15°C, 25°C, 35°C, and 45°C. After the reaction started, 400 μL of gas was collected from the reactor and the efficiency of photocatalytic H2 was detected using gas chromatography (GC-7900). The hydrogen production performance at different temperatures is shown in Figure 2. Figure 9 shown.

[0092] Example 19 Photothermal Performance Test

[0093] (1) Using infrared thermal imaging technology to analyze Ni / NiO x @C cocatalyst photothermal activation performance. x @C, g-C3N4, Ni / NiO of Example 7 x @C / g-C3N4 were placed in the same environment, and the surface temperature of the catalyst was photographed by an infrared thermal imaging camera. -2 Under the strong xenon lamp, record the catalyst surface temperature after 1 minute of irradiation, then record it every 2 minutes, and finally record it every 3 minutes. Figure 10 As shown, active samples C, Ni / NiO x @C, g-C3N4 and Ni / NiO x The temperature of @C / g-C3N4 increased from room temperature to 90.6℃, 157.9℃, 66.2℃ and 128.1℃, respectively, indicating that Ni / NiO x @C has remarkable photothermal conversion efficiency.

[0094] (2) Using infrared thermal imaging technology to analyze Ni / NiO x @C co-catalyst photothermal activation performance. Figure 11 As shown in the figure, after 40 minutes of simulated sunlight exposure, Ni / NiO x The temperature of the @C / g-C3N4 system increased from room temperature to 36.76°C, which is 5.55°C higher than that of pure g-C3N4, indicating that the photothermal effect induced by the co-catalyst is conducive to achieving local thermal activation.

[0095] (3) Temperature control test shows that Ni / NiO x The photothermal activation performance of the @C cocatalyst was tested by testing the hydrogen evolution performance of the composite photocatalysts of g-C3N4, Example 7, Example 10, Example 11, and Example 12 at 15°C, 25°C, 35°C, and 45°C. Figure 12 The Arrhenius formula of Ni / NiO was fitted to obtain x The activation energy of @C / g-C3N4 is significantly lower than that of g-C3N4.

Claims

1. A double-defect Ni / NiO x @C catalyst, characterized in that The double defect Ni / NiO x @C catalyst is Ni / NiO with core-shell structure x @C, which has Ni and O double vacancy defects, and effectively constructs active sites with hindered Lewis acid-base pairs under the spatial confinement of the graphene coating; The preparation method of the catalyst comprises the following steps: (1) The nickel source, citric acid, anhydrous ethanol and water are fully mixed and dissolved and then dried to obtain a precursor gel; (2) annealing the precursor gel in an inert atmosphere to obtain double-defect Ni / NiO x @C catalyst; The annealing temperature is 300° C.-450° C., and the annealing time is 4-10 hours.

2. A double-defect Ni / NiO according to claim 1 x @C catalyst, characterized in that The double defect Ni / NiO x The particle size of @C catalyst is 5~10nm.

3. A double-defect Ni / NiO according to claim 1 or 2 x @C catalyst preparation method, characterized in that, The steps include: (1) The nickel source, citric acid, anhydrous ethanol and water are fully mixed and dissolved and then dried to obtain a precursor gel; (2) annealing the precursor gel in an inert atmosphere to obtain double-defect Ni / NiO x @C catalyst; The annealing temperature is 300° C.-450° C., and the annealing time is 4-10 hours.

4. The preparation method according to claim 3, characterized in that The annealing temperature is 400° C. and the annealing time is 8 hours.

5. The preparation method according to claim 3, characterized in that The nickel source is nickel acetate; the water is deionized water; the mass ratio of the nickel source to citric acid is (3-6):10; the gelation condition is drying in a forced air oven at 70-80° C. for 3-24 hours to obtain the precursor gel; and the inert atmosphere is high-purity Ar gas.

6. A composite photocatalyst, characterized in that It comprises a main catalyst and a co-catalyst, wherein the co-catalyst is a double-defect Ni / NiO as claimed in claim 1 or 2. x @C catalyst; the main catalyst is g-C3N4.

7. A composite photocatalyst according to claim 6, characterized in that: The added amount of the co-catalyst accounts for 1% to 9% of the total mass of the composite photocatalyst.

8. Use of the composite photocatalyst according to any one of claims 6 to 7 in photocatalytic water decomposition to produce hydrogen.

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