Ruthenium-hydroxyl iron nickel oxide loaded strontium tantalum nitrogen oxide composite photocatalyst and preparation method thereof

Abstract

The invention belongs to the technical field of photocatalyst synthesis, and particularly discloses a ruthenium-hydroxyl iron nickel oxide loaded strontium tantalum nitrogen oxide composite photocatalyst and a preparation method thereof. The composite photocatalyst is composed of SrTaO2N loaded with a metal Ru and a NiFeLDH cocatalyst. According to the application, SrCl2 and Ta2O5 are taken as precursors, KOH is taken as an additive to regulate and control the formation process of molten salt nitridation SrTaO2N, a metal Ru hydrogen evolution cocatalyst is loaded on the surface of SrTaO2N by adopting a dipping reduction method, and a NiFeLDH oxygen evolution cocatalyst is loaded on the surface of SrTaO2N by adopting a photodeposition method. The method is simple in process and convenient to operate, the obtained SrTaO2N photocatalyst has good crystallinity and visible light absorption performance, metal Ru and NiFeLDH loading improves the hydrogen evolution and oxygen evolution reaction dynamic performance of the photocatalyst, efficient visible light catalysis and full water decomposition are achieved, and the large-scale industrial application value is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocatalyst synthesis, and particularly relates to a ruthenium-hydroxy iron oxide nickel-loaded strontium tantalum nitride oxide composite photocatalyst and a preparation method thereof. Background Art

[0002] Due to the volatility and intermittency of renewable energy such as solar energy, it is necessary to solve the problem of solar energy storage. Solar-driven water splitting to produce hydrogen is a promising technology for solving solar energy storage, which can store solar energy in the form of chemical energy in hydrogen. It can be used as an energy source for various production and living units, and also as a chemical raw material.

[0003] Among various solar hydrogen production technologies that have been studied, the use of particulate semiconductor photocatalysts to directly decompose water to produce hydrogen has shown great advantages due to its large-scale industrial preparation. Considering that visible light occupies more than 40% of the solar spectrum, developing photocatalysts that can effectively utilize visible light is an urgent problem to be solved in the photocatalytic water splitting to produce hydrogen technology. In recent years, perovskite-structured nitrides ABO 2 N have a narrower bandwidth relative to oxides due to the inclusion of the 2p orbitals of N, and different metal elements can be flexibly introduced at the A and B sites, making this type of material have great development potential. Among many ABO 2 N materials, SrTaO 2 N has attracted much attention due to its unique physical and chemical properties, such as appropriate conduction band and valence band positions, ferroelectricity, narrow bandwidth, etc. However, the photocatalytic water splitting performance of SrTaO 2 N is still limited by its high photogenerated carrier recombination. How to improve the quality of SrTaO 2 N crystal particles to reduce the bulk recombination of photogenerated carriers, and to use cocatalysts to modify and enhance the reaction kinetics of hydrogen evolution and oxygen evolution to reduce surface recombination have become the main strategies to improve the water splitting performance of SrTaO 2 N-based photocatalysts. Summary of the Invention

[0004] In view of the technical problems existing in the prior art, the present application proposes a ruthenium-hydroxy iron oxide nickel-loaded strontium tantalum nitride oxide composite photocatalyst and a preparation method thereof.

[0005] The first object of the present application is to provide a ruthenium-hydroxy iron oxide nickel-loaded strontium tantalum nitride oxide composite photocatalyst.

[0006] The second object of the present application is to provide a preparation method of the above ruthenium-hydroxy iron oxide nickel-loaded strontium tantalum nitride oxide composite photocatalyst. This method prepares SrTaO with high crystallinity through a one-step molten salt nitridation method. 2N is simple to operate, and a Ru hydrogen evolution cocatalyst and nickel iron hydroxide oxide (NiFeLDH) oxygen evolution cocatalyst are loaded by microwave method and photodeposition method respectively to prepare a Ru@NiFeLDH@SrTaO 2 N composite photocatalyst. The use of inexpensive nickel iron hydroxide oxide as the oxygen evolution cocatalyst reduces the use of precious metals.

[0007] Another object of the present application is to provide the application of the above-mentioned ruthenium-nickel iron hydroxide oxide loaded strontium tantalum nitride oxide composite photocatalyst in photocatalytic overall water splitting. The composite photocatalyst Ru@NiFeLDH@SrTaO 2 N improves the overall water splitting performance of SrTaO 2 N.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A ruthenium-nickel iron hydroxide oxide loaded strontium tantalum nitride oxide composite photocatalyst, which is composed of SrTaO 2 N loaded with metal ruthenium and nickel iron hydroxide oxide (NiFeLDH) cocatalyst.

[0010] Preferably, the components of the composite photocatalyst are as follows by mass percentage: 1.0% - 5.0% metal Ru cocatalyst, 0.15% - 2.4% NiFeLDH cocatalyst, 93.6% - 98.8% SrTaO 2 N photocatalyst; the average particle size of the SrTaO 2 N is 50 - 1000 nm.

[0011] In a more preferred embodiment of the present invention, the mass percentage of metal Ru is 4.0%, the mass percentage of NiFeLDH is 2.4%, and the mass percentage of SrTaO 2 N is 93.6%.

[0012] Metal Ru has good hydrogen evolution reaction kinetic performance, and NiFeLDH has good oxygen evolution reaction kinetic performance. Its use reduces the use of precious metal cocatalysts, reduces the preparation cost of photocatalysts, and at the same time obtains excellent visible light overall water splitting performance. The Ru@NiFeLDH@SrTaO 2 N composite photocatalyst has good overall water splitting performance mainly due to two reasons. One is that the Ru hydrogen evolution cocatalyst and NiFeLDH oxygen evolution cocatalyst have good catalytic reaction kinetic performance when used in combination with SrTaO 2 N, which reduces the surface recombination of photogenerated carriers. The other is that the SrTaO 2 N photocatalyst prepared by one-step molten salt nitridation method has good crystallinity, which reduces the recombination of bulk photogenerated carriers.

[0013] The present invention also provides a method for preparing the ruthenium-hydroxy iron nickel loaded strontium tantalum oxynitride composite photocatalyst, which specifically includes the following steps:

[0014] S1. Grinding of the precursor mixture: The metal precursor and the additive are fully ground under heating conditions to make them uniformly dispersed, and then dried for use; wherein, the metal precursor consists of SrCl 2 and Ta 2 O 5 , and the additive is KOH;

[0015] S2. Preparation of SrTaO 2 N crystal: The powder ground in step S1 is subjected to high-temperature nitridation under NH 3 in a tube furnace to obtain SrTaO 2 N crystal, which is then washed to remove impurities and dried for use;

[0016] S3. Loading of the metal Ru hydrogen evolution cocatalyst: Weigh the SrTaO 2 N prepared in step S2, add the prepared RuCl 3 aqueous solution thereto, and then add water and absolute ethanol to fully immerse SrTaO 2 N. Stir and ultrasonicate, then heat to evaporate to dryness. The obtained sample is placed in a tube furnace and heated and reduced in a mixed atmosphere of H 2 and N 2 to obtain the SrTaO 2 N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO 2 N;

[0017] S4. Preparation of the Ru@NiFeLDH@SrTaO 2 N composite photocatalyst: Load NiFeLDH by photodeposition method. Using NaIO 3 as the sacrificial agent and KBi buffer solution as the solvent, prepare the NiFeLDH precursor solution. Carry out vacuum photodeposition on the Ru@SrTaO 2 N obtained in step S3. The obtained sample is rinsed and dried, denoted as Ru@NiFeLDH@SrTaO 2 N.

[0018] Preferably, the components in the mixture in step S1 are in parts by weight: SrCl 2 is 0.40 - 1.60 parts, Ta 2 O 5 is 0.55 - 2.21 parts, KOH is 0.035 - 0.14 parts, and SrCl 2 : Ta 2 O 5: The molar ratio of KOH is 2:1:0.5.

[0019] Preferably, the grinding process in step S1 is carried out on a heating table, the temperature is set at 80 - 160 °C, and the grinding time is 20 - 45 min to ensure that the metal precursor and the molten salt are fully mixed and fully dried.

[0020] Preferably, in the tube furnace in step S2, the high-temperature nitridation process under NH 3 atmosphere is as follows: First, NH 3 and N 2 mixed gas is introduced into the tube furnace at room temperature for a period of time. The flow rate of NH 3 is set at 10 - 50 mL / min, and the flow rate of N 2 is set at 50 - 300 mL / min. Then, it is heated to the required nitridation temperature of 850 - 1150 °C, the nitridation time is 2 - 15 h, the heating rate is set at 10 °C / min. After nitridation, it is cooled to 300 °C, and the supply of NH 3 is stopped, and the supply of N 2 is maintained until the temperature drops to room temperature.

[0021] In a preferred embodiment of the present invention, for high-temperature nitridation in the tube furnace under NH 3 atmosphere, the flow rate of NH 3 is set at 40 mL / min, and N 2 is set at 100 mL / min, the nitridation temperature is 950 °C, and the nitridation time is 5 h.

[0022] Preferably, for the cleaning and impurity removal of the product obtained by high-temperature nitridation in the tube furnace in step S2: First, it is ultrasonically cleaned with deionized water for 10 - 30 min, then transferred to a heating table and heated and stirred at 80 - 120 °C, then filtered with deionized water 3 - 5 times, and finally vacuum dried for 3 - 6 h for use.

[0023] Preferably, the concentration of the RuCl 3 aqueous solution in step S2 is 20.32 mg / mL, and the mass ratio of RuCl 3 to SrTaO 2 N is 1:10 - 1:50, and the temperature of impregnation, heating and stirring is set at 80 - 120 °C.

[0024] Preferably, in the tube furnace in step S3, the annealing temperature under H 2 / N 2 atmosphere is 200 - 300 °C, the annealing time is 10 - 60 min, the flow rate of H 2 is 10 - 50 mL / min, and the flow rate of N 2 is 50 - 300 mL / min; More preferably, the annealing temperature is 250 °C, the time is 20 min, and the flow rate of H 2The flow rate is 20 mL / min, N 2 The flow rate is 200 mL / min.

[0025] Preferably, the KBi buffer solution described in step S4 is composed of 0.65 g of boric acid, 0.79 g of KCl, 0.18 g of NaOH, and 150 mL of deionized water; the concentration of the NaIO 3 is 50 mM; the NiFeLDH precursor solution is composed of 1.4542 g of Ni(NO 3 ) 2 ·6H 2 O, 0.1968 g of FeCl 2 ·4H 2 O, and 30 mL of deionized water; 26 - 415 μL of the NiFeLDH precursor solution is added to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 to serve as the photo - deposition solution; more preferably, the volume of the added NiFeLDH precursor solution is 346 μL.

[0026] In a specific embodiment of the present invention, the time of the vacuum photo - deposition in step S4 is 3 h, the light source uses simulated sunlight with a wavelength greater than 400 nm and a power of 100 mW / cm 2 , and the reactor pressure is 5 kPa.

[0027] Preferably, the rinsing in step S4 is carried out through a suction filtration device, rinsed with deionized water and suction - filtered 3 times, and the vacuum drying time is 3 h.

[0028] The present invention also protects the application of the Ru@NiFeLDH@SrTaO 2 N composite photocatalyst in the field of photocatalysis. The Ru@NiFeLDH@SrTaO 2 N composite photocatalyst is applied to the preparation of photocatalytic overall water - splitting materials, and the performance of photocatalytic overall water - splitting for hydrogen and oxygen production is improved.

[0029] For the Ru@NiFeLDH@SrTaO 2 N composite photocatalyst prepared by the present invention, the metal Ru loaded by the impregnation - reduction method has good hydrogen - evolution catalytic activity, which can reduce the surface recombination of photo - generated electrons. The NiFeLDH loaded by photo - deposition has good oxygen - evolution catalytic activity and is inexpensive, which can reduce the preparation cost of the overall catalyst. The SrTaO 2 N photocatalyst prepared by the one - step molten - salt nitridation method has good crystallinity. These above - mentioned factors enable the composite photocatalyst prepared by the present invention to have good overall water - splitting hydrogen - production performance, and the highest hydrogen - production rate can reach 34.6 μmol / g / h.

[0030] Compared with the prior art, the beneficial effects of the present application are:

[0031] (1) The process for preparing SrTaO 2 N in this invention is simple. The SrTaO 2 N is prepared by one-step molten salt nitridation method, which improves its crystallinity and reduces the recombination of bulk carriers.

[0032] (2) The Ru prepared by the impregnation reduction method in this application has good hydrogen evolution catalytic performance; the oxygen evolution cocatalyst uses inexpensive NiFeLDH instead of noble metals, which reduces the preparation cost of the overall composite photocatalyst and has good oxygen evolution catalytic performance.

[0033] (3) This invention realizes the overall water splitting of SrTaO 2 N under the conditions of no sacrificial agent and visible light, which provides material preparation and technical support for the development of visible light overall water splitting, and also provides more possibilities for the practical application of the photocatalytic hydrogen production and oxygen production technology of particulate catalysts. Description of the Drawings

[0034] Figure 1 XRD patterns of the SrTaO 2 N photocatalysts prepared in Examples 1-5.

[0035] Figure 2 SEM pictures of the SrTaO 2 N photocatalysts prepared in Example 2 at different magnifications.

[0036] Figure 3 UV-visible diffuse reflectance spectra of the SrTaO 2 N photocatalysts prepared in Example 2.

[0037] Figure 4 Performance comparison of the overall water splitting photocatalysis of the composite photocatalysts prepared in Examples 1-5 and the photocatalysts in the comparative examples. Detailed Embodiments

[0038] Next, the technical solutions of this invention will be clearly and completely described in combination with the embodiments of this invention. Obviously, the described embodiments are only a part of the embodiments of this invention, rather than all of the embodiments. Based on the embodiments of this invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of this invention.

[0039] The test methods used in the embodiments of this invention are all conventional methods unless otherwise specified; the materials, reagents, etc. used are reagents and materials that can be obtained from commercial channels unless otherwise specified.

[0040] SrCl used in the embodiments of this invention 2 , Ta 2 O5 , KOH, RuCl 3 ,Ni(NO 3 ) 2 6H 2 O, FeCl 2 ·4H 2 O Boric acid, KCl, NaOH, NaIO 3 ,La 2 O 3 All of them were analytically pure. 3 , H 2 and N 2 The purity is 99.99%.

[0041] Example 1

[0042] A ruthenium-iron-nickel oxyhydroxide-supported strontium tantalum oxynitride composite photocatalyst, the specific preparation process is as follows:

[0043] a) 0.40 g SrCl 2 , 0.55g Ta 2 O 5 , 0.035g KOH was placed in a mortar and ground thoroughly on a heating table. The temperature of the heating table was set to 120°C and the grinding time was 30min to make the metal precursor and additives evenly dispersed. Then, the mixture was dried for later use.

[0044] b) SrTaO 2 Preparation of N crystals: The powder ground in step a) is placed in a tube furnace for high-temperature nitridation. First, NH 3 and N 2 Mixed gas for a period of time, NH 3 The flow rate was set to 40 mL / min, N 2 The flow rate was set to 100 mL / min, and the temperature was raised to the required nitriding temperature of 950 °C. The nitriding time was 2 h, and the heating rate was set to 10 °C / min. After the nitriding was completed, the temperature was lowered to 300 °C, and the NH 3 , keep N 2 , until the temperature drops to room temperature. Then the product obtained by high-temperature nitridation in a tube furnace was ultrasonically cleaned with deionized water for 10 minutes, then transferred to a heating table and heated and stirred at 80°C for 30 minutes, then filtered three times with deionized water, and finally vacuum dried for 3 hours to obtain SrTaO 2 N photocatalyst.

[0045] c) Metal Ru hydrogen evolution promoter loading: weigh a certain mass of RuCl 3 Prepare an aqueous solution and weigh 170 mg of SrTaO prepared in step b). 2N was placed in an evaporating dish, and 669 μL of an aqueous solution of RuCl with a concentration of 20.32 mg / mL was added thereto. Then, a certain amount of deionized water and absolute ethanol were added to fully impregnate SrTaO 3 N. It was stirred with a glass rod and sonicated, and then the evaporating dish was placed on a beaker containing 2 / 3 water and heated and stirred at 80 °C until dry. The above sample was scraped off from the evaporating dish and transferred to a crucible, and then placed in a tubular furnace. Annealing was carried out at 250 °C for 20 min under an H 2 / N 2 atmosphere. The flow rate of H 2 was 20 mL / min, and the flow rate of N 2 was 200 mL / min, obtaining a SrTaO 2 N photocatalyst loaded with metallic Ru, denoted as Ru@SrTaO 2 N. 2

[0046] d) Preparation of Ru@NiFeLDH@SrTaO 2 N composite photocatalyst: The NiFeLDH was loaded by photodeposition method. The KBi buffer solution was composed of 0.65 g of boric acid, 0.79 g of KCl, 0.18 g of NaOH and 150 mL of deionized water; the concentration of NaIO 3 was 50 mM; the NiFeLDH precursor solution was composed of 1.4542 g of Ni(NO 3 ) 2 ·6H 2 O, 0.1968 g of FeCl 2 ·4H 2 O and 30 mL of deionized water; 346 μL of the NiFeLDH precursor solution was measured and added to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 to serve as the photodeposition solution. The Ru@SrTaO 2 N sample obtained in step c) was placed in a reaction device and photodeposited for 3 h under simulated sunlight with a wavelength greater than 400 nm and a power of 100 mW / cm 2 . The obtained sample was rinsed with deionized water and dried for use, denoted as Ru@NiFeLDH@SrTaO 2 N, and the components were 4.0%, 2.4%, and 93.6% by mass percentage.

[0047] Example 2

[0048] A ruthenium-hydroxy iron nickel-loaded strontium tantalum nitride oxide composite photocatalyst, and the specific preparation process is as follows:

[0049] a) 0.80 g of SrCl 2 , 1.10 g of Ta​2 O 5 、 0.07 g of KOH was placed in a mortar and ground thoroughly on a heating plate. The temperature of the heating plate was set to 120 °C, and the grinding time was 30 min to uniformly disperse the metal precursor and the additive, and then it was dried for later use.

[0050] b) Preparation of SrTaO 2 N crystal: The ground powder in step a) was placed in a tubular furnace for high-temperature nitridation. First, NH 3 and N 2 mixed gas was introduced into the tubular furnace at room temperature for a period of time. The flow rate of NH 3 was set to 40 mL / min, and the flow rate of N 2 was set to 100 mL / min. Then it was heated to the required nitridation temperature of 950 °C, and the nitridation time was 5 h. The heating rate was set to 10 °C / min. After nitridation, it was cooled to 300 °C, and the flow of NH 3 was stopped, and the flow of N 2 was maintained until the temperature dropped to room temperature. Then the product obtained by high-temperature nitridation in the tubular furnace was ultrasonically cleaned with deionized water for 10 min, then transferred to a heating plate and heated with stirring at 80 °C for 30 min, then filtered three times with deionized water, and finally vacuum dried for 3 h to obtain SrTaO 2 N photocatalyst.

[0051] c) Loading of metal Ru hydrogen evolution cocatalyst: Weigh a certain mass of RuCl 3 to prepare an aqueous solution. Weigh 170 mg of SrTaO 2 N prepared in step b) and place it in an evaporating dish. Add 669 μL of 20.32 mg / mL RuCl 3 aqueous solution to it, and then add a certain amount of deionized water and absolute ethanol to fully impregnate SrTaO 2 N. Stir with a glass rod and ultrasonicate. Then place the evaporating dish on a beaker filled with 2 / 3 water and heat and evaporate with stirring at 80 °C water temperature until it is completely evaporated. Scrape the above sample from the evaporating dish and transfer it to a crucible, and place it in a tubular furnace under H 2 / N 2 atmosphere for annealing at a temperature of 250 °C for 20 min. The flow rate of H 2 is 20 mL / min, and the flow rate of N 2 is 200 mL / min to obtain a SrTaO 2 N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO 2 N.

[0052] d) Ru@NiFeLDH@SrTaO 2Preparation of N composite photocatalyst: NiFeLDH was loaded by photodeposition method. The KBi buffer solution consisted of 0.65 g boric acid, 0.79 g KCl, 0.18 g NaOH and 150 mL deionized water; the concentration of NaIO 3 was 50 mM; the NiFeLDH precursor solution consisted of 1.4542 g Ni(NO 3 ) 2 ·6H 2 O, 0.1968 g FeCl 2 ·4H 2 O and 30 mL deionized water; 346 μL of the NiFeLDH precursor solution was measured and added to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 as the photodeposition solution. The Ru@SrTaO 2 N sample obtained in step c) was placed in a reaction device and photodeposited for 3 h under simulated sunlight with a wavelength greater than 400 nm and a power of 100 mW / cm 2 at a pressure of 5 kPa. The obtained sample was rinsed with deionized water and dried for use, denoted as Ru@NiFeLDH@SrTaO 2 N, and the components were 4.0%, 2.4%, and 93.6% by mass percentage respectively.

[0053] Example 3

[0054] A ruthenium-hydroxy iron nickel loaded strontium tantalum nitride oxide composite photocatalyst, and the specific preparation process is as follows:

[0055] a) 0.80 g of SrCl 2 , 1.10 g of Ta 2 O 5 , and 0.07 g of KOH were placed in a mortar and ground thoroughly on a heating table. The temperature of the heating table was set to 120 °C, and the grinding time was 30 min to make the metal precursors and additives evenly dispersed, and then dried for use.

[0056] b) Preparation of SrTaO 2 N crystal: The powder ground in step a) was placed in a tubular furnace for high-temperature nitridation. First, a mixed gas of NH 3 and N 2 was introduced into the tubular furnace at room temperature for a period of time. The flow rate of NH 3 was set to 40 mL / min, and the flow rate of N 2 was set to 100 mL / min. Then, the temperature was raised to the required nitridation temperature of 950 °C, the nitridation time was 3 h, the heating rate was set to 10 °C / min. After nitridation, the temperature was lowered to 300 °C, the supply of NH 3 was stopped, and the supply of N 2 was maintained., until the temperature drops to room temperature. Then, the product obtained by high-temperature nitridation in the tube furnace is ultrasonically cleaned with deionized water for 10 min, transferred to a heating table, heated and stirred at 80 °C for 30 min, filtered three times with deionized water, and finally dried under vacuum for 3 h to obtain SrTaO 2 N photocatalyst.

[0057] c) Loading of metal Ru hydrogen evolution cocatalyst: Weigh a certain mass of RuCl 3 to prepare an aqueous solution. Weigh 170 mg of SrTaO prepared in step b) 2 N and place it in an evaporating dish. Add 669 μL of 20.32 mg / mL RuCl 3 aqueous solution to it, and then add a certain amount of deionized water and absolute ethanol to fully immerse SrTaO 2 N. Stir with a glass rod and ultrasonicate. Then, place the evaporating dish on a beaker filled with 2 / 3 water, heat and evaporate with stirring at 80 °C water temperature until dry. Scrape the above sample from the evaporating dish and transfer it to a crucible. Place it in a tube furnace and anneal it at 250 °C for 20 min under H 2 / N 2 atmosphere, with an H 2 flow rate of 20 mL / min and an N 2 flow rate of 200 mL / min to obtain a SrTaO loaded with metal Ru 2 N photocatalyst, denoted as Ru@SrTaO 2 N.

[0058] d) Preparation of Ru@NiFeLDH@SrTaO 2 N composite photocatalyst: The NiFeLDH is loaded by photodeposition method. The KBi buffer solution consists of 0.65 g boric acid, 0.79 g KCl, 0.18 g NaOH and 150 mL deionized water; the concentration of NaIO 3 is 50 mM; the NiFeLDH precursor solution consists of 1.4542 g Ni(NO 3 ) 2 ·6H 2 O, 0.1968 g FeCl 2 ·4H 2 O and 30 mL deionized water; measure 346 μL of the NiFeLDH precursor solution and add it to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 as the photodeposition solution. Place the Ru@SrTaO obtained in step c) 2 N sample in the reaction device at a pressure of 5 kPa, with a wavelength greater than 400 nm and a power of 100 mW / cm 2Under simulated sunlight for 3 h of photo-deposition. The obtained sample was rinsed with deionized water and dried for use, denoted as Ru@NiFeLDH@SrTaO 2 N, and the components were 4.0%, 2.4%, and 93.6% by mass percentage, respectively.

[0059] Example 4

[0060] A ruthenium-iron nickel hydroxide loaded strontium tantalum nitride composite photocatalyst, and the specific preparation process is as follows:

[0061] a) 0.80 g of SrCl 2 , 1.10 g of Ta 2 O 5 , and 0.07 g of KOH were placed in a mortar and ground thoroughly on a heating table. The temperature of the heating table was set at 120 °C, and the grinding time was 30 min to uniformly disperse the metal precursors and additives, and then dried for use.

[0062] b) Preparation of SrTaO 2 N crystal: The ground powder in step a) was placed in a tube furnace for high-temperature nitridation. First, NH 3 and N 2 mixed gas was introduced into the tube furnace at room temperature for a period of time. The flow rate of NH 3 was set at 40 mL / min, and the flow rate of N 2 was set at 100 mL / min. Then it was heated to the required nitridation temperature of 950 °C, and the nitridation time was 10 h. The heating rate was set at 10 °C / min. After nitridation, it was cooled to 300 °C, and the NH 3 was stopped, and N 2 was kept flowing until the temperature dropped to room temperature. Then the product obtained by high-temperature nitridation in the tube furnace was ultrasonically cleaned with deionized water for 10 min, then transferred to a heating table and heated and stirred at 80 °C for 30 min, then filtered three times with deionized water, and finally vacuum dried for 3 h to obtain the SrTaO 2 N photocatalyst.

[0063] c) Loading of metal Ru hydrogen evolution cocatalyst: Weigh a certain mass of RuCl 3 to prepare an aqueous solution. Weigh 170 mg of SrTaO 2 N prepared in step b) and place it in an evaporating dish. Add 167 μL of 20.32 mg / mL RuCl 3 aqueous solution to it, and then add a certain amount of deionized water and absolute ethanol to fully immerse SrTaO 2 N. Stir with a glass rod and ultrasonicate. Then place the evaporating dish on a beaker filled with 2 / 3 water and heat and evaporate and stir at 80 °C water temperature until it is evaporated to dryness. Scrape the above sample from the evaporating dish and transfer it to a crucible, and place it in a tube furnace with H 2 / N 2 Annealing temperature is 250 °C for 20 min under H 2 flow rate of 20 mL / min, N 2 flow rate of 200 mL / min, to obtain SrTaO loaded with metal Ru 2 N photocatalyst, denoted as Ru@SrTaO 2 N.

[0064] d) Ru@NiFeLDH@SrTaO 2 Preparation of N composite photocatalyst: NiFeLDH was loaded by photodeposition method. The KBi buffer solution consists of 0.65 g boric acid, 0.79 g KCl, 0.18 g NaOH and 150 mL deionized water; NaIO 3 concentration is 50 mM; the NiFeLDH precursor solution consists of 1.4542 g Ni(NO 3 ) 2 ·6H 2 O, 0.1968 g FeCl 2 ·4H 2 O and 30 mL deionized water; 346 μL of the NiFeLDH precursor solution was measured and added to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 as the photodeposition solution. The Ru@SrTaO 2 N sample obtained in step c) was placed in a reaction device under a pressure of 5 kPa, simulated sunlight with a wavelength greater than 400 nm and a power of 100 mW / cm 2 for 3 h of photodeposition. The obtained sample was rinsed with deionized water and dried for use, denoted as Ru@NiFeLDH@SrTaO 2 N, and the components are 1.0%, 2.4%, and 96.6% by mass percentage.

[0065] Example 5

[0066] A ruthenium-nickel iron hydroxyoxide loaded strontium tantalum nitride composite photocatalyst, the specific preparation process is as follows:

[0067] a) 0.80 g of SrCl 2 , 1.10 g of Ta 2 O 5 , 0.07 g of KOH were placed in a mortar and ground thoroughly on a heating table. The temperature of the heating table was set at 120 °C and the grinding time was 30 min to uniformly disperse the metal precursor and the additive, and dried for use.

[0068] b) SrTaO 2Preparation of SrTaO₃N crystal: The ground powder in step a) is placed in a tubular furnace for high-temperature nitridation. First, NH₃ and N₂ mixed gas is introduced into the tubular furnace at room temperature for a period of time. The flow rate of NH₃ is set at 40 mL / min, and the flow rate of N₂ is set at 100 mL / min. Then, the temperature is raised to the required nitridation temperature of 950 °C, the nitridation time is 15 h, the heating rate is set at 10 °C / min. After nitridation, the temperature is cooled to 300 °C, and the supply of NH₃ is stopped while maintaining the supply of N₂ until the temperature drops to room temperature. Then, the product obtained by high-temperature nitridation in the tubular furnace is ultrasonically cleaned with deionized water for 10 min, transferred to a heating table, heated and stirred at 80 °C for 30 min, filtered three times with deionized water, and finally dried under vacuum for 3 h to obtain SrTaO₃N photocatalyst. 3 and N₂ 2 mixed gas for a while, the flow rate of NH₃ 3 is set at 40 mL / min, and the flow rate of N₂ 2 is set at 100 mL / min. Then, the temperature is raised to the required nitridation temperature of 950 °C, the nitridation time is 15 h, the heating rate is set at 10 °C / min. After nitridation, the temperature is cooled to 300 °C, and the supply of NH₃ 3 is stopped while maintaining the supply of N₂ 2 until the temperature drops to room temperature. Then, the product obtained by high-temperature nitridation in the tubular furnace is ultrasonically cleaned with deionized water for 10 min, transferred to a heating table, heated and stirred at 80 °C for 30 min, filtered three times with deionized water, and finally dried under vacuum for 3 h to obtain SrTaO₃N photocatalyst. 2 N photocatalyst.

[0069] c) Loading of metal Ru hydrogen evolution cocatalyst: Weigh a certain mass of RuCl₃ and configure it into an aqueous solution. Weigh 170 mg of SrTaO₃N prepared in step b) and place it in an evaporating dish. Add 669 μL of 20.32 mg / mL RuCl₃ aqueous solution to it, and then add a certain amount of deionized water and absolute ethanol to fully immerse SrTaO₃N. Stir with a glass rod and ultrasonicate. Then, place the evaporating dish on a beaker filled with 2 / 3 water and heat and evaporate with stirring at 80 °C water temperature until it is completely dried. Scrape the above sample from the evaporating dish and transfer it to a crucible, and place it in a tubular furnace for annealing at 250 °C for 20 min under H₂ / N₂ atmosphere. The flow rate of H₂ is 20 mL / min, and the flow rate of N₂ is 200 mL / min to obtain SrTaO₃N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO₃N. 3 and configure it into an aqueous solution. Weigh 170 mg of SrTaO₃N prepared in step b) 2 and place it in an evaporating dish. Add 669 μL of 20.32 mg / mL RuCl₃ 3 aqueous solution to it, and then add a certain amount of deionized water and absolute ethanol to fully immerse SrTaO₃N. Stir with a glass rod and ultrasonicate. Then, place the evaporating dish on a beaker filled with 2 / 3 water and heat and evaporate with stirring at 80 °C water temperature until it is completely dried. Scrape the above sample from the evaporating dish and transfer it to a crucible, and place it in a tubular furnace for annealing at 250 °C for 20 min under H₂ / N₂ atmosphere. The flow rate of H₂ is 20 mL / min, and the flow rate of N₂ is 200 mL / min to obtain SrTaO₃N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO₃N. 2 N. Stir with a glass rod and ultrasonicate. Then, place the evaporating dish on a beaker filled with 2 / 3 water and heat and evaporate with stirring at 80 °C water temperature until it is completely dried. Scrape the above sample from the evaporating dish and transfer it to a crucible, and place it in a tubular furnace for annealing at 250 °C for 20 min under H₂ / N₂ atmosphere. The flow rate of H₂ is 20 mL / min, and the flow rate of N₂ is 200 mL / min to obtain SrTaO₃N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO₃N. 2 / N₂ 2 atmosphere at an annealing temperature of 250 °C for 20 min. The flow rate of H₂ is 20 mL / min, and the flow rate of N₂ is 200 mL / min to obtain SrTaO₃N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO₃N. 2 flow rate is 20 mL / min, and the flow rate of N₂ 2 is 200 mL / min to obtain SrTaO₃N photocatalyst loaded with metal Ru, denoted as Ru@SrTaO₃N. 2 N photocatalyst, denoted as Ru@SrTaO₃N. 2 N.

[0070] d) Preparation of Ru@NiFeLDH@SrTaO₃N composite photocatalyst: The NiFeLDH is loaded by photodeposition method. The KBi buffer solution is composed of 0.65 g boric acid, 0.79 g KCl, 0.18 g NaOH and 150 mL deionized water; the concentration of NaIO₃ is 50 mM; the NiFeLDH precursor solution is composed of 1.4542 g Ni(NO₃)₂·6H₂O 2 and 150 mL deionized water; the concentration of NaIO₃ is 50 mM; the NiFeLDH precursor solution is composed of 1.4542 g Ni(NO₃)₂·6H₂O 3 and 150 mL deionized water; the NiFeLDH precursor solution is composed of 1.4542 g Ni(NO₃)₂·6H₂O 3 )₂ 2 ·6H₂O 2O, 0.1968 g of FeCl 2 ·4H 2 O and 30 mL of deionized water; 26 μL of the NiFeLDH precursor solution was measured and added to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 as the photo-deposition solution. The Ru@SrTaO 2 N sample obtained in step c) was placed in the reaction device under a pressure of 5 kPa, with a wavelength greater than 400 nm and a power of 100 mW / cm 2 under simulated sunlight for 3 h of photo-deposition. The obtained sample was rinsed with deionized water and dried for use, denoted as Ru@NiFeLDH@SrTaO 2 N, and the components were 4.0%, 0.25%, and 95.75% by mass percentage respectively.

[0071] Comparative Example 1

[0072] A SrTaO 2 N photocatalyst was prepared by the following method:

[0073] a) 0.80 g of SrCl 2 , 1.10 g of Ta 2 O 5 , and 0.07 g of KOH were placed in a mortar and thoroughly ground on a heating table. The temperature of the heating table was set to 120 °C, and the grinding time was 30 min to uniformly disperse the metal precursor and the additive, and then dried for use.

[0074] b) Preparation of SrTaO 2 N crystal: The powder ground in step a) was placed in a tube furnace for high-temperature nitridation. First, a mixed gas of NH 3 and N 2 was introduced into the tube furnace at room temperature for a period of time. The flow rate of NH 3 was set to 40 mL / min, and the flow rate of N 2 was set to 100 mL / min. Then, the temperature was raised to the required nitridation temperature of 950 °C, and the nitridation time was 5 h. The heating rate was set to 10 °C / min. After nitridation, the temperature was lowered to 300 °C, and the supply of NH 3 was stopped, and the supply of N 2 was maintained until the temperature dropped to room temperature. Then, the product obtained by high-temperature nitridation in the tube furnace was ultrasonically cleaned with deionized water for 10 min, then transferred to the heating table and heated and stirred at 80 °C for 30 min, then filtered three times with deionized water, and finally vacuum dried for 3 h to obtain the SrTaO 2 N photocatalyst.

[0075] Comparative Example 2

[0076] A ruthenium-nickel oxyhydroxide-supported strontium tantalum oxide nitrogen composite photocatalyst, the specific preparation process is as follows:

[0077] a) 0.80 g SrCl 2 , 1.10g Ta 2 O 5 , 0.07g KOH was placed in a mortar and ground thoroughly on a heating table with the heating table temperature set to 120°C for 30 minutes to evenly disperse the metal precursor and additives, and dried for later use.

[0078] b) SrTaO 2 Preparation of N crystals: The powder ground in step a) is placed in a tube furnace for high-temperature nitridation. First, NH 3 and N 2 Mixed gas for a period of time, NH 3 The flow rate was set to 40 mL / min, N 2 The flow rate was set to 100 mL / min, and the temperature was raised to the required nitriding temperature of 950 °C. The nitriding time was 15 h, and the heating rate was set to 10 °C / min. After the nitriding was completed, the temperature was lowered to 300 °C and the NH 3 , keep N 2 , until the temperature drops to room temperature. Then the product obtained by high-temperature nitridation in a tube furnace was ultrasonically cleaned with deionized water for 10 minutes, then transferred to a heating table and heated and stirred at 80°C for 30 minutes, then filtered three times with deionized water, and finally vacuum dried for 3 hours to obtain SrTaO 2 N photocatalyst.

[0079] c) Metal Ru hydrogen evolution promoter loading: weigh a certain mass of RuCl 3 Prepare an aqueous solution and weigh 170 mg of SrTaO prepared in step b). 2 N was placed in an evaporating dish and 669 μL of 20.32 mg / mL RuCl was added to it. 3 Aqueous solution, then add a certain amount of deionized water and anhydrous ethanol to make SrTaO 2 N is fully impregnated, stirred with a glass rod and ultrasonicated, then the evaporating dish is placed on a beaker filled with 2 / 3 water and heated at 80℃ for evaporation and stirring until it is evaporated to dryness. The above sample is scraped off the evaporating dish and transferred to a crucible, which is placed in a tube furnace for H 2 / N 2 The annealing temperature is 250℃, the time is 20min, and the H 2 The flow rate is 20mL / min, N 2 The flow rate was 200 mL / min, and SrTaO loaded with metal Ru was obtained. 2 N photocatalyst, denoted as Ru@SrTaO 2N.

[0080] d) Ru@NiLDH@SrTaO 2 Preparation of N composite photocatalyst: NiLDH was loaded by photodeposition method. The KBi buffer solution consisted of 0.65 g boric acid, 0.79 g KCl, 0.18 g NaOH and 150 mL deionized water; the concentration of NaIO 3 was 50 mM; the NiLDH precursor solution consisted of 1.4542 g Ni(NO 3 ) 2 ·6H 2 O and 30 mL deionized water; 393 μL of the NiLDH precursor solution was measured and added to 150 mL of the KBi buffer solution containing 50 mM NaIO 3 as the photodeposition solution. The Ru@SrTaO 2 N sample obtained in step c) was placed in a reaction device under a pressure of 5 kPa, under simulated sunlight with a wavelength greater than 400 nm and a power of 100 mW / cm 2 for 3 h of photodeposition. The obtained sample was rinsed with deionized water and dried for use, denoted as Ru@NiLDH@SrTaO 2 N, and the components were 4.0%, 2.4%, and 93.6% by mass percentage respectively.

[0081] Phase characterization and performance test analysis

[0082] As Figure 1 shown, it is the X-ray diffraction pattern (XRD) of the SrTaO 2 N photocatalyst prepared in Examples 1-5. All samples had diffraction peaks at 22.1°, 31.4°, 45.0° and 55.9°, corresponding to the (100), (110), (200) and (211) crystal planes of SrTaO 2 N respectively. From the peak intensity, it can be seen that the samples all had good crystallinity, indicating that the crystallinity of SrTaO 2 N obtained by the one-step molten salt nitridation method was not greatly affected by the absolute mass of the precursor and the nitridation time.

[0083] As Figure 2 shown, it is the scanning electron microscope images of SrTaO 2 N prepared in Example 2 at different magnification. SrTaO 2 N formed single crystal particle structures with different sizes of 50 - 1000 nm.

[0084] As Figure 3 shown, it is the ultraviolet-visible diffuse reflectance spectrum of the SrTaO 2 N photocatalyst prepared in Example 2. It can be seen from the figure that SrTaO prepared by the one-step molten salt nitridation method 2N has good visible light absorption performance, and the optical absorption edge is 617.6 nm.

[0085] The composite photocatalysts prepared in Application Examples 1-5 and the SrTaO 2 photocatalyst without loading hydrogen and oxygen evolution cocatalysts in Comparative Example 1 were used for photocatalytic overall water splitting performance tests. The specific test process is as follows:

[0086] Add 150 mg of the composite photocatalysts prepared in Examples 1-5 to the photocatalytic reactor, and then add 150 mL of deionized water (adjust the pH to 8 by dropping 0.1 M NaOH). The reactor containing the above suspension was evacuated by a vacuum system to remove the interference of dissolved oxygen in the air and water, and then argon was introduced to maintain the pressure in the reactor at 5 kPa. A simulated solar light with a wavelength greater than 400 nm and a power of 100 mW / cm 2 was used as the reaction light source. Samples were taken once an hour for 10 times, and the peak areas of the hydrogen and oxygen chromatographic signals were calculated and recorded respectively to calculate the hydrogen and oxygen yields. As Figure 4 shown, it is the photocatalytic overall water splitting performance of the composite photocatalysts prepared in Examples 1-5 and the SrTaO 2 photocatalyst without loading hydrogen and oxygen evolution cocatalysts in Comparative Example 1 within 10 h of reaction time. It can be seen that the SrTaO 2 photocatalyst without loading hydrogen and oxygen evolution cocatalysts has low photocatalytic hydrogen evolution reaction activity, and the oxygen evolution reaction performance is almost zero, which may be due to the fact that the generated photogenerated holes do not react with water in time and the SrTaO 2 N self-oxidation reaction occurs. The composite photocatalysts loaded with cocatalysts in Examples 1-5 have significantly improved photocatalytic performance compared with pure SrTaO 2 N. The hydrogen production amount of the sample in Example 2 reached 52.0 μmol within 10 h, and the oxygen production amount was 24.7 μmol at the same time, indicating that the NiFeLDH cocatalyst significantly improved the oxygen evolution reaction kinetic performance of pure SrTaO 2 N.

[0087] From the above analysis, it can be seen that the present invention provides a one-step molten salt nitridation method to prepare SrTaO 2 with high crystallinity, and at the same time, a metal Ru hydrogen evolution cocatalyst is modified on its surface by an impregnation reduction method, and a NiFeLDH oxygen evolution cocatalyst is modified on its surface by a photodeposition method. The two significantly improve the photocatalytic overall water splitting performance of SrTaO 2 N.

[0088] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the technical solutions of the present invention, rather than limitations on the specific implementation manners of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the claims of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A ruthenium-iron-nickel oxyhydroxide-supported strontium tantalum oxynitride composite photocatalyst, characterized in that: The composite photocatalyst consists of SrTaO2N loaded with metal Ru co-catalyst and NiFeLDH co-catalyst.

2. The ruthenium-iron-nickel oxyhydroxide-supported strontium tantalum oxynitride composite photocatalyst according to claim 1, characterized in that: The components contained are calculated by mass percentage as follows: 1.0% to 5.0% of metal Ru co-catalyst, 0.15% to 2.4% of NiFeLDH co-catalyst, and 93.6% to 98.8% of SrTaO2N photocatalyst; the average particle size of the SrTaO2N is 50 to 1000nm.

3. A method for preparing the strontium tantalum oxynitride composite photocatalyst supported by ruthenium-iron nickel oxyhydroxide as claimed in claim 1 or 2, characterized in that: The steps include: S1. Preparation of precursor mixture: fully grinding the metal precursor and the additive under heating conditions to make them uniformly dispersed and then drying; wherein the metal precursor is composed of SrCl2 and Ta2O5, and the additive is KOH; S2. Preparation of SrTaO2N crystals: using a tube furnace to perform high-temperature nitridation on the powder ground in step S1 under NH3 to obtain SrTaO2N crystals, which are then cleaned, impurities removed, and dried; S3, loading of metal Ru as hydrogen evolution promoter: taking the SrTaO2N obtained in step S2, adding RuCl3 aqueous solution thereto, then adding water and anhydrous ethanol to fully impregnate the SrTaO2N, stirring and ultrasonicating, then heating and evaporating to dryness, placing the obtained sample in a tube furnace and heating and reducing it in a mixed atmosphere of H2 and N2, to obtain a SrTaO2N photocatalyst Ru@SrTaO2N loaded with metal Ru; S4. Preparation of Ru@NiFeLDH@SrTaO2N composite photocatalyst: NiFeLDH was loaded by photodeposition method, NaIO3 was used as sacrificial agent, KBi buffer solution was used as solvent, NiFeLDH precursor solution was prepared, Ru@SrTaO2N obtained in step S3 was vacuum photodeposited, and the sample was rinsed and dried.

4. The preparation method according to claim 3, characterized in that: The components in the mixture of step S1 are calculated by weight as follows: SrCl2 is 0.40-1.60 parts, Ta2O5 is 0.55-2.21 parts, and KOH is 0.035-0.14 parts; the molar ratio of SrCl2:Ta2O5:KOH is 2:1:0.

5.

5. The preparation method according to claim 3, characterized in that: The grinding process in step S1 is carried out on a heating table at a temperature of 80 to 160° C. and a grinding time of 20 to 45 minutes.

6. The preparation method according to claim 3, characterized in that: The high-temperature nitriding process under NH3 atmosphere in the tubular furnace in step S2 is as follows: first, a mixed gas of NH3 and N2 is passed into the tubular furnace at room temperature for a period of time, with an NH3 flow rate of 10 to 50 mL / min and an N2 flow rate of 50 to 300 mL / min, and then the temperature is raised to the required nitriding temperature of 850 to 1150°C, the nitriding time is 2 to 15 h, the heating rate is 10°C / min, and after the nitriding is completed, the temperature is lowered to 300°C, NH3 is stopped, and N2 is kept passing until the temperature drops to room temperature.

7. The preparation method according to claim 3, characterized in that: The concentration of the RuCl3 aqueous solution in step S2 is 20.32 mg / mL, the mass ratio of RuCl3 to SrTaO2N is 1:10 to 1:50, and the immersion heating and stirring temperature is 80 to 120°C.

8. The preparation method according to claim 3, characterized in that: In step S3, the annealing temperature in the H2 / N2 atmosphere in the tubular furnace is 200-300°C, the annealing time is 10-60 min, the H2 flow rate is 10-50 mL / min, and the N2 flow rate is 50-300 mL / min.

9. The preparation method according to claim 3, characterized in that: In step S4, the KBi buffer solution is composed of 0.65 g boric acid, 0.79 g KCl, 0.18 g NaOH and 150 mL deionized water; the NaIO3 concentration is 50 mM; the NiFeLDH precursor solution is composed of 1.4542 g Ni(NO3)2·6H2O, 0.1968 g FeCl2·4H2O and 30 mL deionized water; 26 to 415 μL of NiFeLDH precursor solution is added to 150 mL of KBi buffer solution containing 50 mM NaIO3 as a photodeposition solution.

10. Use of the ruthenium-iron-nickel oxyhydroxide-supported strontium tantalum oxide nitride composite photocatalyst according to claim 1 in the preparation of a photocatalytic total water decomposition material, characterized in that: The application is photocatalytic decomposition of water to produce hydrogen and oxygen.

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