Oxygen-linked monatomic-oxide transition metal catalyst as well as preparation method and application thereof

Abstract

The invention relates to a preparation method of an oxygen-linked monatomic-oxide transition metal catalyst, which comprises the following steps: adding a molybdenum source into a graphene oxide solution, then adding a zirconium source, stirring to obtain a precursor solution, and carrying out hydrothermal reaction on the precursor solution to obtain a reaction product; and drying a reaction product, and carrying out high-temperature nitridation by adopting a chemical vapor deposition method to obtain the oxygen-linked monatomic-oxide transition metal catalyst. According to the preparation method, ammonium molybdate tetrahydrate and zirconium tetrachloride are used as metal precursors, ammonia gas is used as a nitrogen source, and the oxygen-connected monatomic-oxide transition metal catalyst is synthesized by adopting a hydrothermal reaction and a chemical vapor deposition method. The composite material shows extremely excellent electrocatalytic water electrolysis efficiency, and has remarkable high catalytic activity, reachable large current density, extremely small Tafel slope and high stability.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrocatalytic chemistry, and particularly relates to an oxygen-linked single-atom-oxide transition metal catalyst, a preparation method thereof, and an application thereof. Background Art

[0002] Renewable energy-powered hydrogen production is an effective strategy to alleviate the current energy pressure caused by the large-scale use of fossil fuels in society. Hydrogen, as a new type of energy, has the characteristics of sustainable development. It has a high calorific value when burned, great application potential, and can achieve zero carbon emissions. Among various hydrogen production technologies, water electrolysis for hydrogen production is expected to become the main technical means in the future because it can make full use of renewable and clean energy such as wind energy and solar energy. The hydrogen evolution reaction (HER), as a half-reaction of water electrolysis, requires the assistance of a catalyst to accelerate its slow kinetic process.

[0003] Single-atom catalysts (SACs) have excellent atomic utilization efficiency, customizable electronic states, and superior reaction selectivity, thus significantly improving the catalytic performance. Molybdenum (Mo) is a transition metal element in the 4d block, with variable oxidation states and coordination numbers. Mo SACs have shown great promise in electrocatalysis, especially in the development of electrocatalysts for HER. However, the increase in the surface energy of single atoms and the lack of favorable attachment sites often ultimately lead to the aggregation of metal atoms into nanoparticles or clusters. Recently, the chemical bonding of isolated metal SACs to the compatible surface of highly interacting metal oxides has been proven to be helpful in constructing and preserving SACs in various chemical processes. The strong covalent interaction between single atoms and such a matrix can effectively anchor single atoms and avoid the formation of aggregated particles. ZrO 2 exhibits excellent chemical stability and corrosion resistance in both acidic and alkaline electrolytes, ensuring the long-term durability and operational stability of HER. However, the HER performance of ZrO 2 is restricted due to poor charge transfer and low active sites, limiting the electron transfer efficiency. In particular, metal oxides are more efficient in cleaving the HO-H bond but perform poorly in other important hydrogen adsorption and desorption processes. Controlling oxygen vacancies (V O ) can change the electronic structure, active sites, and surface characteristics of oxygen-containing electrocatalysts, thus greatly improving their efficiency. Therefore, it is promising to select a simple and effective strategy to prepare a single-atom oxide material rich in oxygen vacancy defects for application in HER. Summary of the Invention

[0004] The object of the present invention is to provide an oxygen-linked single-atom-oxide transition metal catalyst, its preparation method and application, which can have high electrocatalytic activity for HER, have excellent catalytic hydrogen evolution reaction performance and good stability in acidic and alkaline pure water and seawater, and at the same time show good performance and stability in an alkaline anion exchange membrane (AEM) electrolytic cell;

[0005] To achieve the above object, the technical solution adopted by the present invention is:

[0006] An oxygen-linked single-atom-oxide transition metal catalyst, its preparation method and application, comprising the following steps:

[0007] S1. Add a molybdenum source to the graphene oxide solution, and then add a zirconium source. After mixing the graphene with the metal solution, ultrasonicate for 20 - 30 min to obtain a precursor solution, and perform a hydrothermal reaction on the precursor solution to obtain a reaction product;

[0008] S2. Dry the reaction product, and then perform high-temperature nitridation by chemical vapor deposition to obtain an oxygen-linked single-atom-oxide transition metal catalyst

[0009] Preferably, the percentage of molybdenum in the molybdenum source in the mass of graphene oxide is 5 - 15%; the percentage of zirconium in the zirconium source in the mass of graphene oxide is 3 - 7%.

[0010] Preferably, the molybdenum source is ammonium molybdate tetrahydrate; the zirconium source is zirconium tetrachloride.

[0011] Preferably, in step S1, the concentration of the graphene oxide solution is 1 - 3 mg / mL.

[0012] Preferably, in step S1, the temperature of the hydrothermal reaction is 160 - 220 °C, and the time of the hydrothermal reaction is 8 - 24 h.

[0013] Preferably, in step S2, the drying treatment is freeze-drying, and the freeze-drying time is 6 - 12 h.

[0014] Preferably, in step S2, the high-temperature nitridation by chemical vapor deposition includes the following steps: perform nitridation in a mixed atmosphere of argon and ammonia, the reaction temperature is 600 - 1000 °C, the reaction time is 1 - 3 h, the argon flow rate is 100 ± 10 sccm, and the ammonia flow rate is 50 ± 10 sccm.

[0015] On the other hand, the present invention provides an oxygen-linked single-atom-oxide transition metal catalyst prepared by the above-mentioned preparation method.

[0016] On the other hand, the present invention provides the use of the oxygen-linked single-atom-oxide transition metal catalysis as a catalyst for the electrocatalytic hydrogen evolution reaction.

[0017] On the other hand, the present invention provides the use of the oxygen-linked single-atom-oxide transition metal catalyst as a cathode catalyst for an anion exchange membrane.

[0018] The present invention uses (NH 4 ) 6 Mo 7 O 24 ·4H 2 O and ZrCl 4 as metal precursors, ammonia (NH 3 ) as a nitrogen source, and synthesizes an oxygen-linked single-atom-oxide transition metal catalyst by a hydrothermal reaction and chemical vapor deposition method. During the chemical vapor deposition process, ZrO 2-x clusters form a large number of oxygen vacancies under high temperature and high pressure, are connected to Mo single atoms through oxygen bridges, and anchor single atoms through defects, exposing more active sites. Due to the strong metal-support interaction between Mo single atoms and the ZrO 2-x substrate, the single-atom-oxide transition metal catalyst has excellent durability, thus further promoting hydrogen production and stability.

[0019] The catalyst prepared by the present invention has rich functional groups, a hydroxyl (-OH) functional group, which can adsorb water molecules through hydrogen bonding and other interactions, making it easier for water molecules to accumulate on the catalyst surface, thereby increasing the concentration of reactants and accelerating the reaction rate. The conjugated carbon-carbon double bond (C═C) functional group can construct an electron delocalization system inside the material. In the hydrogen evolution reaction, good electrical conductivity can ensure that electrons are quickly transferred from the electrode to the catalyst active site, promoting the proton reduction reaction (2H + +2e - →H 2 ), thereby improving the kinetic performance of the hydrogen evolution reaction.

[0020] The catalyst prepared by the present invention has electrocatalytic hydrogen evolution performance and has the advantages of high activity, low onset potential, large current density, small Tafel slope, and stable performance. When used as a catalyst for an anion exchange membrane battery, it exhibits excellent power density and stability, and has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 XRD pattern of the Mo-ZrO 2-x / NG composite material prepared in Example 1;

[0022] Figure 2 For the Mo-ZrO prepared in Example 12-x Raman spectra of Mo-ZrO

[0023] Figure 3 / NG composite prepared in Example 1 2-x Infrared spectra of Mo-ZrO

[0024] Figure 4 / NG composite prepared in Example 1 2-x TEM images of Mo-ZrO

[0025] Figure 5 / NG composite prepared in Example 1, where: a - 500 nm, b - 100 nm 2-x HAADF-STEM images of Mo-ZrO

[0026] Figure 6 / NG composite prepared in Example 1 2-x XPS survey spectra of Mo-ZrO

[0027] Figure 7 / NG composite prepared in Example 1, with the inset showing the schematic diagram of element content 2-x XPS spectra of Mo-ZrO

[0028] Figure 8 / NG composite prepared in Example 1, where: a - Mo 3d, b - Zr 3d, c - N 1s, d - O 1s 2-x Performance test graphs of Mo-ZrO 2 / NG composite as a catalyst in the electrocatalytic hydrogen evolution reaction, where Figure 8a is the polarization curve in 0.5 M H 4 Figure 8c is the polarization curve in 1.0 M KOH electrolyte, Figure 8b is the Tafel curve in 0.5 M H 2 Figure 8d is the Tafel curve in 1.0 M KOH electrolyte, with a scan rate of 50 mV / s 4 In Figure, a is the chronoamperometric long-term stability test cyclic curve of Mo-ZrO

[0029] Figure 9 / NG composite prepared in Example 1 in 0.5 M H 2-x saturated with hydrogen and 1.0 M KOH solutions, and b is the cyclic curve of Mo-ZrO 2 / NG composite prepared in Example 1 in 0.5 M H 4 saturated with hydrogen and 1.0 M KOH solutions 2-x / NG composite prepared in Example 1 in 0.5 M H 2 saturated with hydrogen and 1.0 M KOH solutions 4 solution

[0030] Figure 10 Performance test diagram of the Mo-ZrO 2-x / NG composite material in the electrochemical hydrogen evolution reaction in seawater, where a is the polarization curve in 0.5 M H 2 SO 4 seawater electrolyte, c is the polarization curve in 1.0 M KOH seawater electrolyte, b is the Tafel curve in 0.5 M H 2 SO 4 seawater electrolyte, d is the Tafel curve in 1.0 M KOH seawater electrolyte, and the scanning rate is 50 mV / s;

[0031] Figure 11 Performance test diagram of the Mo-ZrO 2-x / NG composite material in an anion exchange membrane electrolytic cell, and the test conditions are 1.0 M KOH electrolyte;

[0032] Figure 12 Chronoamperometry curve comparison of the Mo-ZrO 2-x / NG composite material prepared in Example 1 in an anion exchange membrane electrolytic cell, the test conditions are 1.0 M KOH electrolyte, and the stability curve under a constant current of 0.3 A cm -2 for 60 h. Detailed implementation manners

[0033] The following further describes the present invention in conjunction with the accompanying drawings and specific embodiments.

[0034] The graphene oxide in the following examples is prepared by the improved Hummers method, and the specific process is as follows: Add 3 g of graphite powder and concentrated H 2 SO 4 and H 3 PO 4 mixed solution (volume ratio 9:1) into a three-necked flask, and slowly add 18 g of KMnO 4 solid under the condition of a rotation speed of 200 - 350 rpm. Set the water bath temperature to 60 °C, the stirring speed to 200 - 350 rpm, and the stirring time to 12 h. After the reaction, let the solution temperature drop to room temperature, pour it into 400 mL of pre-frozen deionized water and stir evenly; Slowly add H 2 O 2 into the solution in small amounts several times until the solution changes from purple to bright yellow; Wash repeatedly with 30% by mass HCl solution, deionized water, absolute ethanol and ether; Vacuum dry at room temperature for 48 h to obtain a pale yellow graphene oxide solid.

[0035] Example 1

[0036] A preparation method of an oxygen-bonded single-atom / oxide transition metal catalyst, comprising the following steps:

[0037] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, successively place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide are 15% and 7% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace, and carry out high-temperature nitridation reaction under the mixed atmosphere of Ar and NH 3 . The reaction parameters are set as follows: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 3 h. Obtain an oxygen-bonded single-atom / oxide transition metal catalyst (Mo-ZrO 2-x / NG).

[0038] Example 2

[0039] A preparation method of an oxygen-bonded single-atom / oxide transition metal catalyst, comprising the following steps:

[0040] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, successively place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide are 10% and 5% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace, and carry out high-temperature nitridation reaction under the mixed atmosphere of Ar and NH 3 . The reaction parameters are set as follows: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 3 h. Obtain an oxygen-bonded single-atom / oxide transition metal catalyst. (Mo-ZrO2-x / NG@5)

[0041] Example 3

[0042] A preparation method of an oxygen-bonded single-atom / oxide transition metal catalyst includes the following steps:

[0043] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, successively place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide are 15% and 3% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace and carry out high-temperature nitridation reaction under a mixed atmosphere of Ar and NH 3 . The reaction parameters are set as follows: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 3 h. Obtain an oxygen-bonded single-atom / oxide transition metal catalyst (Mo-ZrO 2-x / NG@3).

[0044] Example 4

[0045] A preparation method of an oxygen-bonded single-atom / oxide transition metal catalyst includes the following steps:

[0046] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, successively place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide are 5% and 7% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace and carry out high-temperature nitridation reaction under a mixed atmosphere of Ar and NH 3 . The reaction parameters are set as follows: temperature: 800 °C, gas flow rate: NH 3: 50 sccm, Ar: 100 sccm, nitridation duration 3 h. Obtain an oxygen-bonded single-atom - oxide transition metal catalyst (Mo-ZrO 2-x / NG).

[0047] Example 5

[0048] A method for preparing an oxygen-bonded single-atom - oxide transition metal catalyst, comprising the following steps:

[0049] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, successively place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide mass are 5% and 5% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace and carry out high-temperature nitridation reaction under a mixed atmosphere of Ar and NH 3 . The reaction parameters are set as: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration 3 h. Obtain an oxygen-bonded single-atom - oxide transition metal catalyst (Mo-ZrO 2-x / NG@5).

[0050] Example 6

[0051] A method for preparing an oxygen-bonded single-atom - oxide transition metal catalyst, comprising the following steps:

[0052] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, successively place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide mass are 5% and 3% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace and carry out high-temperature nitridation reaction under a mixed atmosphere of Ar and NH 3Perform high-temperature nitridation reaction under a mixed atmosphere. The reaction parameters are set as follows: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 3 h. Obtain an oxygen-linked single-atom-oxide transition metal catalyst (Mo-ZrO 2-x / NG@3).

[0053] Example 7

[0054] A preparation method of an oxygen-linked single-atom-oxide transition metal catalyst includes the following steps:

[0055] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, sequentially place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution into the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide mass are 15% and 7% respectively. Continue ultrasonic treatment for 30 min, then transfer the reaction solution to a hydrothermal autoclave, heat to 180 °C and react for 12 h. After the reaction is completed, cool the hydrothermal autoclave. After freeze-drying the hydrothermal product for 6 h, put the obtained product into a CVD furnace and use chemical vapor deposition technology to perform high-temperature nitridation reaction under a mixed atmosphere of Ar and NH 3 . The reaction parameters are set as follows: temperature: 600 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 3 h. Obtain an oxygen-linked single-atom-oxide transition metal catalyst (Mo-ZrO 2-x / NG-600).

[0056] Example 8

[0057] A preparation method of an oxygen-linked single-atom-oxide transition metal catalyst includes the following steps:

[0058] Add 1.6 g of graphene oxide solid to 80 ml of deionized water. After ultrasonic treatment for 6 h, sequentially place the (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4The solution was placed in the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide were 15% and 7% respectively. Ultrasonic treatment was continued for 30 min, and then the reaction solution was transferred to a hydrothermal autoclave and heated to 180 °C for 12 h. After the reaction was completed, the hydrothermal autoclave was cooled. After the hydrothermal product was freeze-dried for 6 h, the obtained product was placed in a CVD furnace. Using chemical vapor deposition technology, high-temperature nitridation reaction was carried out under a mixed atmosphere of Ar and NH 3 The reaction parameters were set as follows: temperature: 1000 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 3 h. An oxygen-bonded single-atom-oxide transition metal catalyst (Mo-ZrO 2-x / NG-1000) was obtained.

[0059] Example 9

[0060] A preparation method of an oxygen-bonded single-atom-oxide transition metal catalyst includes the following steps:

[0061] 1.6 g of graphene oxide solid was added to 80 ml of deionized water. After ultrasonic treatment for 6 h, (NH 4 ) 6 Mo 7 O 24 ·4H 2 O solution and ZrCl 4 solution were placed in the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide were 15% and 7% respectively. Ultrasonic treatment was continued for 30 min, and then the reaction solution was transferred to a hydrothermal autoclave and heated to 180 °C for 12 h. After the reaction was completed, the hydrothermal autoclave was cooled. After the hydrothermal product was freeze-dried for 6 h, the obtained product was placed in a CVD furnace. Using chemical vapor deposition technology, high-temperature nitridation reaction was carried out under a mixed atmosphere of Ar and NH 3 The reaction parameters were set as follows: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration: 1 h. An oxygen-bonded single-atom-oxide transition metal catalyst (Mo-ZrO 2-x / NG-1h) was obtained.

[0062] Example 10

[0063] A preparation method of an oxygen-bonded single-atom-oxide transition metal catalyst includes the following steps:

[0064] 1.6 g of graphene oxide solid was added to 80 ml of deionized water. After ultrasonic treatment for 6 h, (NH 4 ) 6 Mo7 O 24 ·4H 2 O solution and ZrCl 4 solution were placed in the graphene oxide solution. The mass percentages of Mo and Zr in the graphene oxide were 15% and 7% respectively. Ultrasonic treatment was continued for 30 min, and then the reaction solution was transferred to a hydrothermal autoclave and heated to 180 °C for 12 h. After the reaction was completed, the hydrothermal autoclave was cooled. After freeze-drying the hydrothermal product for 6 h, the obtained product was placed in a CVD furnace, and high-temperature nitridation reaction was carried out under the mixed atmosphere of Ar and NH 3 The reaction parameters were set as follows: temperature: 800 °C, gas flow rate: NH 3 : 50 sccm, Ar: 100 sccm, nitridation duration 2 h. An oxygen-bonded single-atom-oxide transition metal catalyst (Mo-ZrO 2-x / NG-2h) was obtained.

[0065] The following is the catalyst performance evaluation and characterization of Example 1:

[0066] Electrochemical measurements were carried out on an electrochemical workstation (CHI 660E) using a three-electrode system. The oxygen-bonded single-atom-oxide transition metal catalyst obtained in Example 1 was dispersed in 1 mL of water / ethanol with a v / v of 4:1, and then 40 μL of 5 wt% Nafio solution was added. Subsequently, ultrasonic treatment was carried out to form a uniform suspension. Then, 2.5 μL of the dispersion was drop-coated on a glassy carbon electrode. After the first dispersion was dried, another 2.5 μL of the dispersion was drop-coated and loaded onto the glassy carbon electrode (diameter 3 mm). The electrode was dried at room temperature for 12 h before measurement.

[0067] Hydrogen evolution reaction (HER) test:

[0068] In H 2 saturated 0.5 M H 2 SO 4 electrolyte solution, using a carbon rod as the counter electrode and a saturated calomel electrode as the reference electrode, the oxygen-bonded single-atom-oxide transition metal catalyst Mo-ZrO 2-x / NG prepared in Example 1 was used as the working electrode to form a three-electrode system to test the HER performance. Linear sweep voltammetry (LSV) was tested at a scan rate of 50 mV / s. All potentials need to be converted to the standard hydrogen electrode (RHE), and the corresponding formula is: E(RHE) = E(SCE) + (0.242 + 0.059pH).

[0069] In H 2In a saturated 1.0 M KOH electrolyte solution, a carbon rod serves as the counter electrode, and a saturated calomel electrode is used as the reference electrode. The oxygen-linked single-atom-oxide transition metal catalyst prepared in Example 1 is used as the working electrode to form a three-electrode system for testing the HER performance. Linear sweep voltammetry (LSV) is carried out at a scan rate of 50 mV / s. All potentials need to be converted to the standard hydrogen electrode (RHE), and the corresponding formula is = E(SCE) + (0.242 + 0.059pH).

[0070] Anion exchange membrane electrolytic cell test: First, 10 mg of the electrocatalyst, 2000 μL of isopropanol, 200 μL of ultrapure water, and 200 μL of PiperION-B5-HCO 3 solution (5 wt%) are mixed and sonicated for 2 hours to prepare the catalyst ink. Then, the catalyst ink is drop-coated on one side of the carbon paper (Toray H060), and the electrode area is 2*2 cm 2 . Mo-ZrO 2-x / NG is used as the cathode catalyst, and the final catalyst load is 1.0 mg cm -2 . IrO 2 (Sigma-Aldrich) is used as the anode catalyst, and the load is 1 mgcm -2 . The prepared carbon paper with anode and cathode catalysts is placed on the anion exchange membrane ( X37-50 grade 60, Suzhou Shengnuo Technology) for polarization curve and stability tests. During the experiment, the flow rates of H 2 and O 2 are maintained at 0.3 L min -1 . At a constant cell voltage of 0.3 V, the stability of the anion exchange membrane is evaluated.

[0071] As Figure 1 shown, it is the XRD pattern of Mo-ZrO 2-x / NG prepared in Example 1, which confirms that the XRD peaks of ZrO 2-x match well with those of t-type ZrO 2 , and Mo exists in the form of single atoms.

[0072] As Figure 2 shown, it is the Raman spectrum of Mo-ZrO 2-x / NG prepared in Example 1. In the Raman spectrum, the intensity ratio (I 2-x / I D / I G ) of the D band to the G band of Mo-ZrO

[0073] As Figure 3As shown, it is the infrared spectrum of Mo-ZrO 2-x / NG prepared in Example 1. Mo-ZrO 2-x / NG has rich functional groups, such as the hydroxyl (-OH) functional group, which can adsorb water molecules through hydrogen bonding and other interactions, making it easier for water molecules to accumulate on the catalyst surface, thereby increasing the reactant concentration and accelerating the reaction rate. The conjugated carbon-carbon double bond (C=C) functional group can construct an electron delocalization system inside the material. In the hydrogen evolution reaction, good electrical conductivity can ensure that electrons are quickly transferred from the electrode to the catalyst active site, promoting the proton reduction reaction (2H + +2e - →H 2 ), thus improving the kinetic performance of the hydrogen evolution reaction.

[0074] Figure 4 Figures 4a and 4b are the low-magnification and high-magnification TEM images of Mo-ZrO 2-x / NG prepared in Example 1. The morphology of Mo-ZrO 2-x / NG presents a structure with rich folds and corrugations, thus providing a large specific surface area and exposing more active sites.

[0075] As Figure 5 shown, it is the HAADF-STEM image of Mo-ZrO 2-x / NG prepared in Example 1. Mo is uniformly loaded on the ZrO 2-x clusters in the form of single atoms.

[0076] As Figure 6 shown, it is the elemental content schematic diagram of Mo-ZrO 2-x / NG prepared in Example 1, where Zr: 2.28, Mo: 6.27, C: 76.48, N: 9.38, O: 5.59, indicating that each element has been successfully doped into graphene.

[0077] As Figure 7 shown, it is the XPS spectrum of Mo-ZrO 2-x / NG prepared in Example 1. In the Mo 3d spectrum, there are a total of three pairs of deconvoluted peaks. Two pairs of binding energies of 231.7 / 229.1 and 232.9 / 236.0 eV are attributed to Mo 4+ and Mo 6+ respectively, proving the existence of the Mo-O bond, where 232.1 / 230.3 is attributed to Mo 2+ . Mo 3d confirms the coexistence of multiple valence states of Mo. Zr3d shows that Zr coexists in the forms of Zr 4+ and Zr 3+ , proving the coexistence of ZrO 2It has abundant defects. In addition, in the O 1s spectrum, 530.4, 531.1, 531.9, and 533.2 eV are attributed to metallic O (Mo-O / Zr-O), V O , C-O, and O-H respectively, confirming the existence of Mo-O and Zr-O. The above results can prove that Mo single atoms and ZrO 2-x are connected by an oxygen bridge and are tightly combined. For the deconvoluted N 1s spectrum, pyridine N (398.6 eV), pyridine N (400.0 eV), and graphitic N (401.7 eV), and Mo-N (397.0 eV) confirm the coordination of Mo atoms and N atoms. And the change of the N configuration is beneficial to optimizing the local electronic structure.

[0078] As Figure 8 shown in Figs. 8a and 8c, they are the polarization curves of the composite material as a catalyst in 0.5 H 2 SO 4 electrolyte and 1.0 M KOH electrolyte respectively. It can be seen that the low overpotentials of the catalyst at a current density of 10 mA cm -2 in acidic and alkaline electrolytes are 22 and 23 mV respectively. From Figure 8 Figs. 8b and 8d, it can be seen that the composite material prepared by the present invention has low Tafel slopes in both acidic and alkaline electrolytes, which are 31 and 32 mV / dec respectively, proving that the catalyst exhibits good hydrogen evolution catalytic activity under acidic conditions.

[0079] As Figure 9 shown in Fig. 9a, it is the cyclic voltammetry curves of the catalyst prepared in Example 1 in 0.5 H 2 SO 4 solution saturated with hydrogen and 1.0 M KOH solution. After 10,000 cycles, the performance degradation of the catalyst can be ignored, proving that the prepared catalytic material has excellent cyclic stability. As Figure 9 shown in Fig. 9b, it is the chronoamperometry long-term stability test of the catalyst prepared by the present invention in 0.5 H 2 SO 4 solution saturated with hydrogen and 1.0 M KOH solution. It can be seen that the material prepared by the present invention has almost no attenuation of the polarization current compared with the initial value after 30 h of testing under constant current, showing good long-term stability.

[0080] As Figure 10 shown in Figs. 10a and 10c, they are the polarization curves of the composite material as a catalyst in 0.5 H 2 SO 4 and 1.0 M KOH seawater respectively. It can be seen that the overpotentials of the catalyst at a current density of 10 mA cm -2 in acidic and alkaline seawater electrolytes are 36 and 29 mV respectively. From Figure 10It can be seen from b and 10d that the composite material prepared by the present invention has low Tafel slopes in both acidic and alkaline seawaters, which are 35 and 34 mV dec, respectively. -1 This proves that the catalyst exhibits good hydrogen evolution catalytic activity under seawater conditions.

[0081] As Figure 11 shown, the polarization curve of the Mo-ZrO 2-x / NG catalyst prepared in Example 1 under an anion exchange membrane electrolyzer device. Using the above catalyst as the cathode catalyst of the anion exchange membrane electrolyzer, at 70 °C and a current density of 0.5 A / cm 2 , only a voltage of 1.93 V is required.

[0082] As Figure 12 shown, the Mo-ZrO 2-x / NG catalyst prepared in Example 1 was continuously operated for 60 hours in an anion exchange membrane electrolyzer (1.0 M KOH electrolyte) at a constant current density of 0.3 A cm -2 . Its voltage decay rate can be ignored, indicating that Mo-ZrO 2-x / NG has both high activity and long-term stability in the alkaline electrolyzed water system, proving that the catalyst not only exhibits excellent catalytic activity and stable performance, but also shows great potential at the practical application level and has good application prospects.

Claims

1. A method for preparing an oxygen-linked single atom-oxide transition metal catalyst, characterized in that: The following steps are involved: S1. Adding a molybdenum source to a graphene oxide solution, and then adding a zirconium source and stirring to obtain a precursor solution, and subjecting the precursor solution to a hydrothermal reaction to obtain a reaction product; S2. Dry the reaction product, and then perform high-temperature nitridation using a chemical vapor deposition method to obtain an oxygen-connected single atom-oxide transition metal catalyst.

2. The preparation method according to claim 1, characterized in that: The percentage of molybdenum in the molybdenum source to the mass of graphene oxide is 5-15%; the percentage of zirconium in the zirconium source to the mass of graphene oxide is 3-7%.

3. The preparation method according to any one of claims 1 or 2, characterized in that The molybdenum source is ammonium molybdate tetrahydrate; and the zirconium source is zirconium tetrachloride.

4. The preparation method according to claim 1, characterized in that: In step S1, the concentration of the graphene oxide solution is 1-3 mg / mL.

5. The preparation method according to claim 1, characterized in that: In step S1, the temperature of the hydrothermal reaction is 160-220° C., and the time of the hydrothermal reaction is 8-24 hours.

6. The preparation method according to claim 1, characterized in that: In step S2, the drying process is freeze drying, and the freeze drying time is 6 to 12 hours.

7. The preparation method according to claim 1, characterized in that: In step S2, the high-temperature nitridation using chemical vapor deposition method includes the following steps: nitridation is carried out in a mixed atmosphere of argon and ammonia, the reaction temperature is 600-1000°C, the reaction time is 1-3h, the argon flow rate is 100±10sccm, and the ammonia flow rate is 50±10sccm.

8. An oxygen-linked single atom-oxide transition metal catalyst prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the oxygen-linked single atom-oxide transition metal catalyst according to claim 8 as a catalyst for electrocatalytic hydrogen evolution reaction.

10. Use of the oxygen-linked single atom-oxide transition metal catalyst according to claim 8 as a cathode catalyst for an anion exchange membrane.

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