Nanopore array induced hydrogen tungsten bronze proton sponge electrode and preparation method and application thereof

Abstract

The invention discloses a nanopore array induced hydrogen tungsten bronze proton sponge electrode and a preparation method and application thereof. A two-dimensional layered nanosheet with a nanopore array is adopted, and the nanopore array induced hydrogen tungsten bronze proton sponge electrode material catalyst is obtained. The nanopore array induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst can provide insertion, storage and removal of active hydrogen due to a layered structure and multiple oxygen vacancies, reinforces combination with NO to generate ammonia, has a relatively high electrochemical active area, can meet most important parameters required by practical application, and has a wide application prospect. As an electrocatalyst, the catalyst has good catalytic performance when being used for flue gas nitrogen oxide electroreduction, high Faraday efficiency can be achieved, and nitrogen oxide can be stably catalyzed to generate ammonia.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal material preparation and application, and relates to a nanopore array-induced hydrogen tungsten bronze proton sponge electrode, a preparation method thereof, and an application thereof. Background Art

[0002] Flue gas, exhaust gas, and other waste gases contain large amounts of nitrogen oxides, a major atmospheric pollutant whose accumulation in the atmosphere severely damages the ecological environment. Conventional selective catalytic reduction (SCR) technology can effectively convert NO into harmless N2, but this requires the consumption of NH3 or H2. Furthermore, ammonia is considered an essential chemical in agriculture and an emerging hydrogen storage carrier. Its industrial synthesis relies on the energy-intensive and carbon-intensive Haber-Bosch process. Therefore, electrochemically reducing NO pollutants, which have a lower fracture energy, to ammonia (NO→NH3) offers a win-win approach for both environmental remediation and pollutant remediation.

[0003] The key to the conversion of NO to ammonia lies in the addition of active hydrogen. It is reasonable to design a hydrogen cycle involving the generation, transfer and consumption of active hydrogen. Metal oxides are of great significance in many important catalytic systems. The generation of active hydrogen on the oxide surface is always accompanied by hydrogen embedding. Under sufficient reducing conditions, hydrogen can penetrate deep into the oxide structure for transfer and storage. x Phase transitions of WO3 have been well reported via rapid and reversible H intercalation, where H atoms can be incorporated as W-OH species with Brønsted acidity. x WO3 can serve as an ion-electron reservoir and proton sponge to construct a dynamic proton-concentrating microenvironment, which further affects the reaction pathway and barrier. Using WO3 for hydrogen circulation can not only ensure sufficient *H supply for NO electrocatalytic reduction, but also alleviate the competitive HER caused by dense *H coverage on the catalyst surface.

[0004] Currently, traditional H x WO3 has the problem that *H insertion and removal are difficult and the hydrogen storage capacity is small. x WO3 is of great significance in many important catalytic systems due to its excellent conductivity and multi-electron vacancies. Therefore, in-depth research and development in this area is very necessary. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a method for preparing a hydrogen tungsten bronze proton sponge electrode material induced by a nanopore array. The electrocatalyst prepared by this method can provide rich insertion, storage and removal of active hydrogen, strengthen the combination with NO to generate ammonia, have a high electrochemical active area, can meet most of the important parameters required for practical applications, and has good catalytic performance as an electrocatalyst for the electric reduction of nitric oxide.

[0006] In a first aspect, the present invention provides a method for preparing a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst, which specifically comprises the following steps: Step S1: preparing a layered nano-KIT-6 template; Step S2: dispersing the layered nano KIT-6 template in an organic solvent, then adding an aqueous ammonium metatungstate solution and reacting under stirring; after the reaction is completed, filtering to obtain a solid product, eluting with an organic solvent and then drying, mixing with elemental sulfur and then thermally annealing to obtain a layered nanoporous array transition metal sulfide; Step S3: etching the layered nanopore array transition metal sulfide with hydrofluoric acid and performing hot air oxidation to obtain a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material.

[0007] Preferably, the concentration of the aqueous ammonium metatungstate solution in step S2 is 45-65 wt%.

[0008] Preferably, in step S2, the mass ratio of the KIT-6 template to elemental sulfur is 1:1-1:2; and the thermal annealing is performed in a hydrogen atmosphere at a temperature of 500-700° C. for 2 h.

[0009] Preferably, the organic solvent in step S2 is cyclohexane.

[0010] Preferably, in step S3 , the etching is performed using hydrofluoric acid with a concentration of 8-15 wt %.

[0011] In a second aspect, the present invention provides a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst, which is prepared using the above method.

[0012] In a third aspect, the present invention provides an application of a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst in the electroreduction of nitric oxide to generate ammonia.

[0013] Preferably, the application specifically adopts a three-electrode system, with carbon paper coated with a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst as the working electrode, nickel foam as the counter electrode, Ag / AgCl as the reference electrode, a flow cell, and the electrolyte is a potassium hydroxide solution. Nitric oxide is first bubbled for a period of time to saturate it, and then nitric oxide is introduced, and a voltage of 0 to -0.4 V vs. RHE is applied.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1) This paper constructs a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material. The nanopore array is rich in oxygen vacancies that can serve as Lewis acid sites to adsorb and store active hydrogen. The electronic interaction between the layered H atoms and adjacent Ru-Cu metal nanoclusters promotes the deprotonation kinetics of the Brønsted acid, which is used for the overflow and regeneration of H, facilitates the full combination with NO, and realizes the catalytic conversion of flue gas nitrogen oxides. The continuous supply of H* greatly improves the Faradaic efficiency and yield of NO to ammonia.

[0015] 2) The micron material provided by the present invention is easy to prepare, low in cost, and environmentally friendly.

[0016] 3) The present invention can stably catalyze nitric oxide to produce ammonia under low NO concentration conditions, and thus has broad application prospects in the electrolytic removal of flue gas nitrogen oxides and nitrogen resource recovery. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a transmission electron microscope (TEM) image of the layered nanopore array KIT-6 obtained in Example 1 of the present invention.

[0018] Figure 2 This is a transmission electron microscope (TEM) image of the layered nanoporous array transition metal sulfide obtained in Example 1 of the present invention.

[0019] Figure 3 This is an X-Ray powder crystal diffraction (XRD) pattern of the layered nanoporous array transition metal sulfide obtained in Example 2 of the present invention.

[0020] Figure 4 This is an X-Ray powder crystal diffraction (XRD) pattern of the hydrogen tungsten bronze proton sponge electrode material electrocatalyst induced by the nanopore array obtained in Example 2 of the present invention.

[0021] FIG5 is a transmission electron microscope (TEM) image of the hydrogen tungsten bronze proton sponge electrode material electrocatalyst induced by the nanopore array obtained in Example 3 of the present invention; (a) and (b) are transmission electron microscope (TEM) images at 500 nm and 200 nm sizes, respectively.

[0022] FIG6 (a) and (b) are the linear sweep voltammetry (LSV) and Faraday efficiency (FE) diagrams of the hydrogen tungsten bronze proton sponge electrode material electrocatalyst induced by the nanopore array obtained in the present invention. DETAILED DESCRIPTION

[0023] As mentioned above, in view of the shortcomings of the existing technology, the inventors of this case proposed the technical solution of the present invention after long-term research and extensive practice, which is mainly based on at least: The present invention utilizes a hydrogen tungsten bronze proton sponge electrode induced by a nanopore array for the electrolytic removal of nitrogen oxides from flue gas and nitrogen resource recovery. The present invention utilizes a two-dimensional layered nanosheet with a nanopore array to obtain a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material catalyst. Due to its layered structure and multiple oxygen vacancies, the nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst of the present invention can provide for the insertion, storage, and removal of active hydrogen, enhancing its combination with NO to form ammonia. It has a high electrochemical active area, sufficient to meet most of the important parameters required for practical applications. As an electrocatalyst for the electroreduction of nitrogen oxides from flue gas, it exhibits excellent catalytic performance, can achieve high Faradaic efficiency, and stably catalyzes nitrogen oxides to form ammonia.

[0024] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0025] In a first aspect, a method for preparing a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst is provided, which specifically comprises the following steps: Step S1: preparing a layered nano-KIT-6 template; Step S2: Dispersing the layered nano KIT-6 template in cyclohexane, then adding an aqueous ammonium metatungstate solution and reacting under stirring; after the reaction is completed, filtering to obtain a solid product, eluting with an organic solvent and drying, then mixing with elemental sulfur, and thermally annealing at 500-700°C for 2 hours under a hydrogen atmosphere to obtain a layered nanoporous transition metal sulfide; wherein the mass ratio of the KIT-6 template to the elemental sulfur is 1:1-2; Step S3: The layered nanopore array transition metal sulfide is etched with 8-15 wt % hydrofluoric acid, washed with water and ethanol, and then placed in a 50° C. oven for drying for 6-12 hours for hot air oxidation to obtain a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material.

[0026] In the second aspect, a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst is provided, which is prepared using the above method.

[0027] The third aspect provides an application of a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst in the electroreduction of nitric oxide to produce ammonia.

[0028] The application specifically adopts a three-electrode system, with carbon paper coated with a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst as the working electrode, nickel foam as the counter electrode, Ag / AgCl as the reference electrode, a flow cell, and the electrolyte is potassium hydroxide solution. Nitric oxide is first bubbled for a period of time to saturate it, and then nitric oxide is introduced, and a voltage of 0 to -0.4 V vs. RHE is applied.

[0029] In addition, it should be noted that the specific embodiments of the present invention described below do not limit the scope of protection of the present invention. Any other corresponding changes and modifications made based on the technical concept of the present invention should be included in the scope of protection of the claims of the present invention.

[0030] Example 1: Layered nanopore array porous silicon material 15 g of P-123 was placed in a 1000 mL beaker, followed by 630 g of purified water and 30 mL of concentrated hydrochloric acid, and stirred at 45°C. 20 g of n-butanol was then added to the solution, stirring continued, followed by 50 g of tetraethyl orthosilicate. After stirring for 24 hours, the resulting turbid solution and white precipitate were transferred to a 1000 mL reagent bottle and hydrothermally heated in a 100°C oven for 24 hours. The solution was then allowed to cool to room temperature in air and filtered. The filtration was washed with ethanol to obtain a white solid, which was then dried in an oven at 50°C for 12 hours. After drying, the solid was heated in a tube furnace at a rate of 1.5°C / min to 550°C under air atmosphere and then held at this temperature for 5 hours to obtain the layered nano-KIT-6 template.

[0031] The obtained layered nanopore array KIT-6 was analyzed by TEM. Figure 1 As shown; Example 2: Preparation of 8-Layered Nanopore Array Transition Metal Sulfide To a 150 mL beaker, add 1 g of the layered nanostructured KIT-6 template, followed by 50 mL of cyclohexane. Stir at room temperature for 0.5 h to ensure uniform dispersion of the mesoporous KIT-6 template in the cyclohexane. While stirring, quickly add 1 mL of a 45-65 wt% aqueous solution of ammonium metatungstate and continue stirring for 2-3 h. After stirring, filter and rinse with cyclohexane. The resulting white solid is vacuum-dried at 60°C for 5 h to yield a white powder, representing the layered nanostructured transition metal sulfide.

[0032] The obtained layered nanoporous transition metal sulfide was analyzed by TEM. Figure 2 As shown; The structure of the obtained layered nanoporous array transition metal sulfide was analyzed by XRD. Figure 3 As shown; Example 3: Synthesis of Nanopore Array-Induced Hydrogen Tungsten Bronze Proton Sponge Electrode Material Electrocatalyst The solution reduction method was used to prepare the prepared layered nanoporous array transition metal sulfide. 10 mL of methanol solution, RuCl3·H2O and CuCl2 metal molar ratio of 1:9-1:8 were added to the prepared layered nanoporous array transition metal sulfide, and ultrasonic dispersion was performed. The mixture was maintained in a 60°C water bath for 12 hours. After cooling to room temperature, 0.1 mM sodium borohydride was added. Finally, thermal annealing was performed in an air atmosphere at 350-450°C for 0.5 hours. The size, morphology and microstructure of the resulting nanoporous array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst are shown in Figure 2. Figure 4 , as shown in Figure 5.

[0033] Application Example 1: Application of Nanopore Array-Induced Hydrogen Tungsten Bronze Proton Sponge Electrode Material Electrocatalyst in the Electroreduction of Nitric Oxide The hydrogen tungsten bronze proton sponge electrode material electrocatalyst induced by the nanopore array prepared in Example 3 was applied to the electroreduction of nitric oxide: The electrochemical test was performed at room temperature using a standard three-electrode system. The electrolytic cell used in the electrochemical test was a closed flow cell. The two electrodes of the electrolytic cell were separated by an anion exchange membrane, which only allowed anions to pass through. 2 The catalyst used carbon paper as the working electrode, nickel foam as the counter electrode, and Ag / AgCl as the reference electrode. The electrolyte was 1 M potassium hydroxide. In the NO reduction experiment, NO was first bubbled for 20 minutes to saturate the metal. A current of -0.1 A was then applied to the metal for reduction. Cyclic voltammetry was then performed for activation, followed by LSV testing at a scan rate of 5 mV / s. Subsequently, NO reduction was performed at various potentials (0 to -0.4 V vs. RHE) to determine the reduction products and their Faradaic efficiencies. The gaseous reduction products were detected by UV colorimetry.

[0034] The Faradaic efficiency of nitric oxide electroreduction products is calculated as follows: Where F is the Faraday constant (96485 C mol -1 ), The NH4 produced + concentration, V is the volume of catholyte (25 mL), t is the reduction time (1 h), and Q is the total charge passing through the electrode.

[0035] The results are shown in Figure 6. The Faradaic efficiency of ammonia at -0.4~-0.8 V vs. RHE reaches more than 90%, indicating that the nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst has good catalytic efficiency in the application of nitric oxide electroreduction.

[0036] The specific embodiments described above further illustrate the technical problems, technical solutions and beneficial effects solved by the present invention. It should be understood that the above are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst, characterized in that: The method comprises the following steps: Step S1: preparing a layered nano-KIT-6 template; Step S2: dispersing the layered nano KIT-6 template in an organic solvent, then adding an aqueous ammonium metatungstate solution and reacting under stirring; after the reaction is completed, filtering to obtain a solid product, eluting with an organic solvent and then drying, mixing with elemental sulfur and then thermally annealing to obtain a layered nanoporous array transition metal sulfide; Step S3: etching the layered nanopore array transition metal sulfide with hydrofluoric acid and performing hot air oxidation to obtain a nanopore array-induced hydrogen tungsten bronze proton sponge electrode material.

2. The preparation method according to claim 1, characterized in that The concentration of the ammonium metatungstate aqueous solution in step S2 is 45-65 wt%.

3. The preparation method according to claim 1, characterized in that In step S2, the mass ratio of the KIT-6 template to elemental sulfur is 1:1-1:

2.

4. The preparation method according to claim 1, characterized in that In step S2, the thermal annealing is performed in a hydrogen atmosphere at a temperature of 500-700° C. for 2 hours.

5. The preparation method according to claim 1, characterized in that In step S2, the organic solvent is cyclohexane.

6. The preparation method according to claim 1, characterized in that In step S3 , the etching is performed using hydrofluoric acid with a concentration of 8-15 wt %.

7. The preparation method according to claim 1, characterized in that The temperature of hot air oxidation in step S3 is 50° C. and the time is 6-12 hours.

8. A nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst, characterized in that: The method is prepared according to any one of claims 1 to 7.

9. Use of the nanopore array-induced hydrogen tungsten bronze proton sponge electrode material electrocatalyst as claimed in claim 8 in the electroreduction of nitric oxide to produce ammonia.

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