CN118292046A - A self-supporting metal sulfide nanocatalytic material and its application in hydrogen production by electrolysis - Google Patents

Abstract

The invention relates to the technical field of electrolytic hydrogen production, and discloses a self-supporting metal sulfide nano catalytic material and application thereof in electrolytic hydrogen production; the catalytic material is formed by distributing nanospheres modified by metal sulfides on the surface of a metal substrate; the catalytic material is obtained by immersing a metal substrate in a treatment liquid and then burning the metal substrate by flame; the soaking solution comprises a combustible solvent, an iron source and a load source; the load source includes a sulfur source and/or a tungsten source. The invention can simply and rapidly convert the low-cost commercial metal substrate into the high-activity and high-stability oxygen evolution catalyst; the problems of low catalytic performance, unstable structure, easy falling of active substances, performance reduction and the like of the conventional OER electrocatalyst can be effectively solved.

Description

A self-supporting metal sulfide nanocatalytic material and its application in hydrogen production by electrolysis

Technical Field

The invention relates to the technical field of electrolytic hydrogen production, and in particular to a self-supporting metal sulfide nanocatalytic material and an application thereof in electrolytic hydrogen production.

Background technique

As a green energy carrier, hydrogen (H ₂ ) has the characteristics of clean and low carbon (no harmful substances such as carbon dioxide are produced when burned), high calorific value (about 3 times that of gasoline), light weight, wide source (can be produced through water electrolysis, fossil fuel recovery and other methods), flexible storage (can appear in the form of liquid, solid, gas, metal hydride, etc., which can greatly meet various scenarios). Therefore, hydrogen energy is expected to replace traditional fossil fuels and alleviate energy crisis and environmental pollution. Promoting the development of hydrogen energy is also considered an indispensable choice for achieving energy transformation.

Hydrogen production by water electrolysis is the process of using renewable electricity such as solar energy and wind energy to split water molecules ( _H2O ) into _H2 (hydrogen evolution reaction, HER) and _O2 (oxygen evolution reaction, OER). This route is a sustainable and environmentally friendly hydrogen production technology. OER is slower than HER because of the rigid OO double bond and multi-step electron transfer process in the OER process. The delayed kinetic process will seriously hinder the overall water decomposition and significantly reduce the total energy conversion efficiency of hydrogen production by water electrolysis. Since the anode catalyst material is the key factor affecting the catalytic performance of OER, finding a class of anode metal materials with high electrocatalytic performance to accelerate the OER reaction kinetics is crucial to improving the total energy conversion efficiency of water electrolysis.

In the study of OER electrocatalytic materials, it was found that _IrO2 and _RuO2 greatly accelerated the water electrolysis process, but their applications were limited due to their high cost and scarcity. In recent years, non-precious metal catalysts that are more in line with the needs of industrial applications (such as low cost, high abundance, high catalytic activity, etc.) have attracted much attention and are regarded as a promising alternative to precious metal catalysts. However, under high current density conditions, the OER electrocatalytic active substances of most non-precious metal electrocatalysts are easily lost into the electrolyte, resulting in a sharp attenuation of the electrocatalytic activity. In order to meet the strict requirements of industrial production, it is extremely necessary to explore non-precious metal materials with higher chemical and mechanical stability, especially those that can operate stably for a long time at current densities greater than 100 mA cm ^-2 .

Among various non-precious metal electrocatalysts, metal sulfides have good conductivity and excellent oxygen evolution performance. Sulfur can change the local structure of metal hydroxides (forming a nanosphere structure modified by nanoparticles) and the chemical structure (the MS bond energy in metal sulfides is weaker than the MO bond energy in metal oxides, resulting in faster reaction kinetics of transformation in metal sulfide electrode materials). On the other hand, sulfur atoms share dispersed ions with neighboring metal ions to balance the electron density of active sites, regulate the quantum spin state of e _g electrons, optimize the adsorption strength and reaction activity of OH*, O*, and OOH* intermediates, effectively reduce the energy barrier of the reaction rate determining step, and change the traditional oxygen adsorbent reaction mechanism. The introduction of sulfur can break the scaling relationship of the proportional size of O*/OOH*, decouple the originally synchronous electron-proton reaction steps, induce an efficient lattice oxygen reaction mechanism, and ultimately greatly improve the OER reaction kinetics and reaction effect.

Although previous studies have made significant progress in modifying metal sulfides and revealing reaction mechanisms, there are still severe challenges in further improving reaction performance and large-scale industrial applications. These powdered metal sulfides usually require the use of poorly conductive adhesives (such as Nafion) to form a catalyst layer on a conductive substrate, which inevitably buries some active centers, increases electrode resistance, and inhibits mass/charge transfer. At the same time, most metal sulfur catalysts have problems such as nanostructure collapse, irregular catalyst aggregation, oxidative decomposition, metal active phase precipitation, and catalyst shedding, which ultimately lead to a decrease in the catalytic efficiency of metal sulfide catalysts and poor stability.

In order to circumvent the above disadvantages, the metal sulfide phase can be firmly fixed on the commercial metal substrate without the use of adhesives to form a self-supporting OER catalyst. At present, hydrothermal (or solvothermal) methods, inert atmosphere high temperature annealing sulfurization method and electrodeposition method are widely used to prepare self-supporting metal sulfide electrode materials. However, these methods usually require a lot of energy consumption (heat and electricity), special chemicals, high-precision reaction equipment, high temperature and high pressure inert atmosphere and other harsh reaction conditions, as well as complex synthesis steps. The synthesized electrode materials usually have problems such as uneven distribution and low catalytic activity, making it difficult to strike a balance between activity and economic cost, thus limiting their industrial application.

Summary of the invention

Technical problems solved by the present invention:

It is used to solve the problems of high energy consumption, harsh reaction conditions, and complex synthesis steps in the existing preparation process of metal sulfide catalysts, as well as the performance degradation of the prepared sulfide samples due to structural instability and loss of active fluids.

The technical solution adopted by the present invention is:

In view of the above technical problems, the purpose of the present invention is to provide a self-supporting metal sulfide nanocatalytic material and its application in hydrogen production by electrolysis. The specific scheme is as follows:

First, the present invention provides a self-supporting metal sulfide nanocatalytic material, wherein metal sulfide-modified nanospheres are distributed on the surface of a metal substrate;

The catalytic material is obtained by soaking a metal substrate in a treatment liquid and then burning it with a flame; the soaking liquid includes a combustible solvent, an iron source, and a load source;

The load source includes a sulfur source and/or a tungsten source. In the above, the flame is burned until the flame is naturally extinguished, and then the metal substrate is naturally cooled, washed with deionized water, and then dried. In the above-mentioned immersion solution, the immersion time of the metal substrate in the immersion solution is about 2 minutes.

In the present invention, the diameter of the nanosphere is 0.51-3.47 μm, the metal sulfide exists in the form of nanoparticles, and the diameter of the nanoparticles is about 160-280 nm. In the present invention, the gap between adjacent nanospheres is 0.7-1.7 μm.

In the present invention, the surface of the nanosphere is rich in mesoporous structure.

In the present invention, the metal substrate includes at least one of nickel-molybdenum foam, nickel foam, iron foam, aluminum foam, titanium foam, cobalt foam, steel foam and copper foam.

In the present invention, both the load source and the iron source can be dissolved in a combustible solvent; and the soaking liquid has the following characteristics:

The iron source includes at least one of ferric chloride, ferric sulfate, and ferric nitrate; the load source can be at least one of a sulfur source and a tungsten source. When it is a sulfur source, the sulfur source includes at least one of potassium thiocyanate and sulfonamide; when it is a tungsten source, the tungsten source includes sodium tungstate. The combustible solvent includes a lower alcohol; in detail, the lower alcohol specifically includes at least one of methanol, ethanol, n-propanol, isopropanol, and propenol; and/or, the lower alcohol includes at least one of methanol and ethanol; and/or, the lower alcohol includes ethanol.

In the aforementioned soaking solution, when the load source is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0-0.4mol/L:0-0.5 mol/L:10 mL; and/or, when the load source is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0-0.4mol/L:0.3-0.5 mol/L:10 mL; and/or, when the load source is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0-0.3mol/L:0.3-0.5 mol/L:10 mL; and/or, when the load source is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0-0.3mol/L:0-0.3 mol/L:10 mL; and/or, when the load source is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0.3 mol/L:0.3 mol/L:10 mL; and/or, when the load is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0.2 mol/L:0.5 mol/L:10 mL.

In the aforementioned immersion solution, when the load source is a tungsten source, the ratio of the tungsten source, the iron source, and the lower alcohol is 0-5 g: 0-0.5 mol/L: 10 mL; and/or, when the load source is a tungsten source, the ratio of the tungsten source, the iron source, and the lower alcohol is 5 g: 0-0.5 mol/L: 10 mL; and/or, when the load source is a tungsten source, the ratio of the tungsten source, the iron source, and the lower alcohol is 0-5 g: 0.5 mol/L: 10 mL; and/or, when the load source is a tungsten source, the ratio of the tungsten source, the iron source, and the lower alcohol is 5 g: 0.5 mol/L: 10 mL.

Second, the present invention provides an application of the aforementioned self-supporting metal sulfide nanocatalytic material in hydrogen production by electrolysis.

The technical mechanism and beneficial effects adopted by the present invention are as follows:

The present invention makes full use of the heat released by the combustion of the immersion liquid (load source, iron source, combustion solvent) to functionalize the surface of the metal substrate (commercial metal substrates such as nickel-molybdenum foam and nickel foam can be used here) into a rich metal sulfide phase. After sulfurization, the original smooth metal substrate surface is modified and roughened by metal sulfide particles, and finally forms a hierarchical mesoporous structure, which is conducive to the diffusion and penetration of the electrolyte, and the rapid release and departure of the generated bubbles.

The present invention rapidly converts cheap commercial metal substrates into highly active and stable oxygen evolution catalysts. Nanospheres modified with metal sulfide particles are directly grown and evenly arrayed on a commercial metal foam substrate, strongly bonded to the substrate, and can effectively solve the problems of structural instability, easy shedding, and performance degradation in existing OER electrocatalysts.

The present invention uses commercial metal foam as the substrate material and flame as the reaction vessel. Under high-temperature spontaneous combustion conditions, the surface of the metal foam substrate is functionalized into a rich metal sulfide phase. Since the self-supporting electrode avoids the use of a binder, the material surface has more exposed active sites, lower electrode resistance and higher mass/charge transfer efficiency.

The present invention uses soaking liquid as the treatment liquid. The soaking liquid has the advantages of low toxicity, low corrosiveness and low cost. The flame generated by ignition is used as a reaction vessel. It can react quickly in an air environment and can produce self-supporting metal sulfide nanoelectrode materials with excellent oxygen evolution performance in high yield within three minutes at the fastest. This method effectively avoids harsh synthesis conditions such as high temperature and high pressure, strong acid and alkali, long time (several days), multiple steps, high-precision equipment, and inert atmosphere. The synthesis method has the advantages of high repeatability, cheap synthetic raw materials, simple operation, easy amplification, short preparation cycle, and low energy consumption. Therefore, it has a broader prospect for industrial application.

The three-dimensional spherical metal sulfide formed by the present invention has high electrical conductivity, large specific surface area and strong mechanical strength, which can effectively make up for the shortcomings of the two-dimensional planar substrate. In the present invention, the strong interface effect between the metal sulfide and the substrate skeleton can effectively prevent the active phase from falling off the electrode surface during the bubble escape process; at the same time, the strong interface electronic coupling can ensure the rapid migration of electrons, greatly reducing the charge transfer impedance value during the reaction process. In addition, due to the absence of non-conductive adhesives, more electrochemical active sites will be fully exposed, which is conducive to close contact between the electrolyte and the active sites, and significantly improves the oxygen evolution reaction performance.

The metal sulfide material obtained by the present invention (labeled as Fe _x /NM-S1 _y ; where x is the molar number of iron salt and y is the molar number of sulfur source) has a distinct three-dimensional hierarchical structure, abundant electroactive sites, excellent conductivity, strong interface binding force, and significant electronic structure modification effect, providing significant OER performance and long-term stability. The overpotential of Fe _0.5M /NM-S1 _0.2M at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 is 228.43 mV and 257.12 mV, respectively, which is better than the commercial nickel-molybdenum foam substrate (423.43 mV and 533.12 mV). The overpotential required at a current density of 100 mA cm ^-2 is only 276.05 mV. Under constant current polarization conditions, Fe _0.5M /NM-S1 _0.2M can work stably for at least 1400 hours at an industrial-grade current density of 0.5 A cm ^-2 without obvious performance degradation, which indicates that the OER reaction performance of commercial metal substrates after fast combustion sulfurization is greatly improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a diagram of the LSV polarization curves of various test samples;

FIG2 is an enlarged view of the dotted box area in FIG1 ;

FIG3 is a LSV polarization curve diagram of Fe _x /NM-S1 _y and commercial nickel-molybdenum foam (NM) in Example 1;

FIG4 is an overpotential diagram of oxygen evolution reaction (OER) of Fe _x /NM-S1 _y and commercial nickel-molybdenum foam (NM) in Example 1;

FIG5 is a stability test diagram of Fe _0.5M /NM-S1 _0.2M in Example 1;

FIG6 is a LSV polarization curve diagram of (Fe _x /NM-S2 _y ) in Example 2;

FIG7 is an overpotential diagram of the oxygen evolution reaction (OER) of Fe _x /NM-S2 _y in Example 2;

FIG8 is a stability test diagram of Fe _0.3M /NM-S2 _0.3M in Example 2;

FIG9 is a LSV polarization curve of (Fe _x /NM-W) in Example 3;

FIG10 is an overpotential diagram of Fe _x /NM-W oxygen evolution reaction (OER) in Example 3;

FIG11 is a diagram of the LSV polarization curves of (Fe _x /NM-S1 _y -a; Fe _x /NM-S1 _y ) in Example 4;

FIG12 is a diagram of the oxygen evolution reaction (OER) overpotential of Fe _x /NM-S1 _y -a; Fe _x /NM-S1 _y in Example 4;

FIG13 is a diagram showing the LSV polarization curves of Fe1 _x /NM-S1 _y and Fe _x /NM-S1 _y in Example 5;

FIG14 is a diagram showing the overpotential of the oxygen evolution reaction (OER) of Fe1 _x /NM-S1 _y ; Fe _x /NM-S1 _y in Example 5;

FIG15 is a LSV polarization curve diagram of ( _Fex /NF- _S1y ) in Example 6;

FIG16 is an overpotential diagram of the Fe _x /NF-S1 _y (OER) reaction in Example 6;

FIG17 is a stability test diagram of Fe _0.5M /NF-S1 _0.2M in Example 6;

Figure 18 (ad) and its insets are SEM images of NM, Fe _0.5M /NM, Fe _0.5M /NM-S1 _0.2M and Fe _0.5M /NM-S1 _0.2M after stability test;

Figure 19 (a) is the TEM image of Fe _0.5M /NM-S1 _0.2M catalytic material, (bf) correspond to Area 1-5 in Figure (a), and (g) is the SAED image of Fe _0.5M /NM-S1 _0.2M .

Figure 20 is the elemental mapping spectrum of Fe _0.5M /NM-S1 _0.2M , (a) is a dark field photo, (b) is the position overlay of all elements, and (cg) correspond to the elements Ni, Mo, Fe, S, O, and N respectively.

Detailed ways

In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

Example 1

A self-supporting metal sulfide nanomaterial, and a preparation method thereof, comprising the following steps: dissolving 0-2 mmol potassium thiocyanate and 0-5 mmol ferric chloride in 10 ml ethanol to obtain a pretreatment solution, soaking a commercial nickel molybdenum substrate (NM) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo = 17:3) in the obtained pretreatment solution (2 min), taking out the soaked commercial nickel molybdenum substrate, igniting it with an open flame, waiting for the flame to extinguish naturally, and the sample to cool naturally, then rinsing it with deionized water, wiping off the attached liquid with filter paper, and air-drying it at room temperature to obtain a sample (the sample is marked as Fe _x /NM-S1 _y ; x is the mole number of ferric chloride, and y is the mole number of potassium thiocyanate). The sample under the optimal synthesis conditions (i.e., 2 mmol potassium thiocyanate, 5 mmol ferric chloride and 10 ml ethanol) is marked as Fe _0.5M /NM-S1 _0.2M .

The proportions of the specific parameters in Example 1 are shown in Table 1.

Table 1 Parameter ratio table

Serial number Potassium thiocyanate/mmol Ferric chloride/mmol Ethanol/mL Soaking time/min 1-1 2 5 10 2 1-2 0 5 10 2 1-3 0 0 10 2

Example 2

The difference between this embodiment and embodiment 1 is that 0-3 mmol yellow amide and 0-3 mmol ferric chloride are dissolved in 10 ml of ethanol to obtain a pretreatment solution. A commercial nickel-molybdenum substrate (NM) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo=17:3) is soaked in the obtained pretreatment solution for 2 min, then ignited under an open flame, and the flame is extinguished naturally. The sample is cooled, then rinsed with deionized water, and the attached liquid is wiped off with filter paper. The sample is air-dried at room temperature to obtain a sample (the sample is marked Fe _x /NM-S2 _y ; where x is the mole number of ferric chloride and y is the mole number of yellow amide). The sample with the best synthesis conditions (i.e., 3 mmol yellow amide, 3 mmol ferric chloride and 10 ml of ethanol) is marked as Fe _0.3M /NM-S2 _0.3M . The ratio of each specific parameter in embodiment 2 is shown in Table 2.

Table 2 Parameter ratio table

Serial number Xanthanamide/mmol Ferric chloride/mmol Ethanol/mL Soaking time/min 2-1 3 3 10 2 2-2 0 3 10 2 2-3 0 0 10 2

Example 3

The difference between this embodiment and embodiment 1 is that 5 mmol of ferric chloride is first dissolved in 10 mL of ethanol to obtain a pretreatment solution. A commercial nickel-molybdenum substrate (NM) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo=17:3) is immersed in the obtained pretreatment sample, ignited with an open flame, and after the flame is naturally extinguished, it is fully rinsed with deionized water, and the attached liquid is wiped off with filter paper, and air-dried at room temperature to obtain Fe _0.5M /NM. Then 5 g of sodium tungstate and 10 ml of ethanol are added to the crucible, and Fe _0.5M /NM is inserted into the undissolved sodium tungstate salt layer, and ethanol is ignited under an open flame. After the flame is naturally extinguished, the sample is cooled, and the attached liquid is wiped off with filter paper. The sample is air-dried at room temperature to obtain the final sample Fe _0.5M /NM-W. The ratios of the specific parameters in embodiment 3 are shown in Tables 3 and 3.5 (Table 3 is the ratio of the parameters in the first step, and Table 3.5 is the ratio of the parameters in the second step).

Table 3 Parameter ratio table

Serial number Ferric chloride/mmol Ethanol/mL Soaking time/min 3-1 5 10 2 3-2 5 10 2 3-3 0 10 2

Table 3.5 Parameter ratio table

Serial number Sodium tungstate/g Ethanol/mL 3-1 5 10 3-2 0 10 3-3 0 10

Example 4

The difference between this embodiment and embodiment 1 is that 3 mmol potassium thiocyanate and 5 mmol ferric chloride are dissolved in 10 ml ethanol or 10 ml methanol to obtain a pretreatment solution. A commercial nickel molybdenum substrate (NM) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo=17:3) is soaked in the obtained pretreatment solution for 2 min, then ignited under an open flame, and the flame is extinguished naturally. The sample is cooled and then rinsed with deionized water, and the attached liquid is wiped off with filter paper. The sample is air-dried at room temperature to obtain a sample (the sample treated with methanol as the solution is marked as: Fe _x /NM-S1 _y -a; the sample treated with ethanol as the solution is marked as Fe _x /NM-S1 _y , where x is the mole number of ferric chloride and y is the mole number of potassium thiocyanate). The ratio of each specific parameter in embodiment 4 is shown in Table 4.

Table 4 Parameter ratio table

Example 5

The difference between this embodiment and embodiment 1 is that 2 mmol potassium thiocyanate, 5 mmol ferric chloride or 5 mmol ferric sulfate are dissolved in 10 ml ethanol to obtain a pretreatment solution. A commercial nickel molybdenum substrate (NM) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo=17:3) is soaked in the obtained pretreatment solution for 2 min, then ignited under an open flame, and the flame is extinguished naturally. The sample is cooled and then rinsed with deionized water, and the attached liquid is wiped off with filter paper. The sample is air-dried at room temperature to obtain a sample (the sample treated with ferric sulfate as the iron salt is marked as: Fe1 _x /NM-S1 _y ; the sample treated with ferric chloride as the iron salt is marked as Fe _x /NM-S1 _y , where x is the molar number of the iron source and y is the molar number of potassium thiocyanate). The ratio of each specific parameter in embodiment 5 is shown in Table 5.

Table 5 Parameter ratio table

Serial number Potassium thiocyanate/mmol Iron sulfate/mmol Ferric chloride/mmol Ethanol/ml Soaking time/min 5-1 2 0 5 10 2 5-2 2 5 0 10 2

Example 6

The difference between Example 6 and Examples 1 and 2 is that 0-4 mmol potassium thiocyanate and 0-5 mmol ferric chloride are dissolved in 10 mL ethanol to obtain a pretreatment solution. Commercial nickel foam (NF) (Suzhou Zhengtai Rong Scientific Research New Materials) is immersed in the obtained pretreatment solution (2 min), ignited with an open flame, and after the flame is naturally extinguished, it is fully rinsed with deionized water, and the attached liquid is wiped off with filter paper. The sample is air-dried at room temperature to obtain a sample (the sample is marked Fe _x /NF-S1 _y ; x is the mole number of ferric chloride, and y is the mole number of potassium thiocyanate). The sample with the best synthesis conditions (2 mmol potassium thiocyanate, 5 mmol ferric chloride and 10 ml ethanol) is marked as Fe _0.5M /NF-S1 _0.2M . The ratio of each specific parameter in Example 6 is shown in Table 6.

Table 6 Parameter ratio table

Test example

1. CV, LSV and EIS tests

Taking the metal sulfide (Fe _x /NM-S1 _y ) catalytic material in Example 1 as an example, a performance test was conducted.

The test process is as follows: In a 1M KOH electrolyte (prepared with distilled water), a three-electrode system is used for performance testing, with the metal sulfide electrocatalytic material as the working electrode, the saturated Hg/HgO electrode as the reference electrode, and the platinum sheet as the counter electrode. At room temperature, the Wuhan Corrtest Studio 6 electrochemical workstation is used to test the oxygen evolution reaction (OER) performance of the electrocatalytic material.

The test results are shown in Table 7 and Figure 1. In order to more intuitively distinguish the LSV curves, we enlarged the black dashed box area in Figure 1 and marked it as Figure 2. The results show that this technology successfully prepared metal sulfide electrocatalysts using the solvent combustion method, and its OER performance was significantly improved. The optimal synthesis conditions were 2 mmol potassium thiocyanate, 5 mmol ferric chloride, 10 ml ethanol, and a commercial nickel-molybdenum substrate as the self-supporting material. It was immersed in the treatment solution for 2 min and ignited with an open flame.

Table 7 Oxygen evolution overpotential test results

Performance tests were conducted using the metal sulfide Fe _x /NM-S1 _y catalytic material (1-1) in Example 1, the metal oxide Fe/NM catalytic material (1-2) and a commercial nickel-molybdenum substrate NM (1-3) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo = 17:3).

The test process is the same as above, and CV, LSV, EIS and i-t tests are performed. The test results are shown in Figures 3 to 5.

Figure 3 shows the LSV polarization curve of Fe _x /NM-S1 _y . It can be concluded from the figure that Fe _0.5M /NM-S1 _0.2M has excellent OER performance. At low current density, the starting potential of Fe _0.5M /NM-S1 _0.2M is significantly lower than that of Fe _0.5M /NM and NM catalysts. As the voltage increases, the increase in current density of Fe _0.5M /NM-S1 _0.2M is more obvious than that of Fe _0.5M /NM and NM.

Figure 4 is an overpotential diagram. It can be seen from Figure 4 that the overpotential of Fe _0.5M /NM-S1 _0.2M at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 is 228.43 mV and 257.12 mV, respectively, which is better than Fe _0.5M /NM (279.9 mV and 318.22 mV) and NM (423.43 mV and 533.12 mV). The overpotential of Fe _0.5M /NM-S1 _0.2M at a current density of 100 mA cm ^-2 is only 276.05 mV, which is twice as good as the NM substrate (555.7 mV).

Figures 3 and 4 further show that sulfidation of the catalyst using the ethanol combustion method can significantly improve the catalytic activity of the catalyst (the overpotential of Fe _0.5M /NM-S1 _0.2M is 51.47 mV, 61.1 mV, and 65.41 mV lower than that of Fe _0.5M /NM at current densities of 10 mA cm ^-2 , 50 mA cm ^-2 , and 100 mA cm ^-2 , respectively).

Figure 5 shows the constant potential polarization curve of Fe _0.5M /NM-S1 _0.2M . At an industrial current density of 0.5 A cm ^-2 , Fe _0.5M /NM-S1 _0.2M can operate stably for at least 1400 hours. The long-term operation at such an industrial high current density reflects that the catalytic material has excellent structural stability and good commercial application prospects.

Performance tests were conducted using the metal sulfide Fe _0.3M /NM-S2 _0.3M catalytic material (2-1) in Example 2, the metal oxide Fe _0.3M /NM catalytic material (2-2) and a commercial nickel-molybdenum substrate NM (2-3) (Kunshan Dingsheng Chemical Materials Co., Ltd., Ni:Mo = 17:3).

The test process is the same as above, and CV, LSV, EIS and i-t tests are performed. The test results are shown in Figures 6 to 8.

Figure 6 shows the LSV polarization curve of Fe _0.3M /NM-S2 _0.3M . It can be seen from the figure that Fe _0.3M /NM-S2 _0.3M has excellent OER performance. Similarly, at low current density, the onset potential of Fe _0.3M /NM-S2 _0.3M is significantly lower than that of Fe _0.3M /NM and NM catalysts.

Figure 7 is an overpotential diagram. It can be seen from Figure 7 that the overpotentials of Fe _0.3M /NM-S2 _0.3M at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 are 239.51 mV and 267.86 mV, respectively, which are better than commercial nickel molybdenum foam NM (423.43 mV and 533.12 mV) and 282.56 mV at a current density of 100 mA cm ^-2 . At the same current density, the overpotential required for the commercial nickel molybdenum substrate (NM) catalyst is about twice that of Fe _0.3M /NM-S2 _0.3M .

Figure 8 is a constant potential polarization curve of Fe _0.3M /NM-S2 _0.3M . At an ultra-large industrial-level current density of 1 A cm ^-2 , Fe _0.3M /NM-S2 _0.3M can operate stably for at least 1100 hours.

Figures 6-8 further demonstrate that the ethanol combustion method can dope different sulfides (xanthocyanamides) into nickel-molybdenum materials and obtain OER catalytic materials with stable performance and high catalytic activity.

Performance tests were conducted using the metal sulfide Fe _0.5M /NM-W catalytic material (3-1) in Example 3, the metal oxide Fe _0.5M /NM catalytic material (3-2) and commercial nickel-molybdenum foam NM (3-3).

The test process is the same as above, and CV, LSV and EIS tests are performed. The test results are shown in Figures 9 and 10.

Figure 9 shows the LSV polarization curves of Fe _0.5M /NM-W, Fe _0.5M /NM and commercial nickel-molybdenum foam NM. It can be seen from the figure that Fe _0.5M /NM-W has excellent OER performance, and Fe _0.5M /NM-W has a smaller overpotential at the same current density. This means that the ethanol combustion method can smoothly incorporate tungsten into commercial nickel-molybdenum substrates and has better catalytic activity. It also shows that the ethanol combustion method can be widely extended to other heteroatom doping.

Figure 10 is an overpotential diagram. It can be seen from Figure 10 that the overpotentials of Fe _0.5M /NM-W at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 are 244.04 mV and 271.02 mV, respectively, which are better than the catalytic material (Fe _0.5M /NM) without tungsten added (279.90 mV and 318.22 mV).

Figures 9 and 10 further show that more importantly, other metal elements can be incorporated into the commercial nickel-molybdenum substrate using the ethanol combustion method to obtain OER catalytic materials with higher catalytic activity.

The performance tests were conducted on the metal sulfide Fe _0.5M /NM-S1 _0.2M catalytic material (4-1) prepared using ethanol as fuel in Example 4 and the metal sulfide Fe _0.5M /NM-S1 _0.2M -a catalytic material (4-2) prepared using lower alcohol (methanol) as fuel.

The test process is the same as above, and CV, LSV, EIS and i-t tests are performed. The test results are shown in Figures 11 and 12.

Figure 11 shows the LSV polarization curves of Fe _0.5M /NM-S1 _0.2M and Fe _0.5M /NM-S1 _0.2M -a. It can be seen from the figure that Fe _0.5M /NM-S1 _0.2M has excellent OER performance. Similarly, at low current density, the starting potential of Fe _0.5M /NM-S1 _0.2M -a is significantly higher than that of Fe _0.5M /NM-S1 _0.2M catalyst. Since the combustion calorific value of methanol is lower than that of ethanol, the OER performance of the sample treated with methanol as fuel is low.

Figure 12 is an overpotential diagram. It can be seen from Figure 12 that the overpotential of Fe _0.5M /NM-S1 _0.2M -a at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 is 261.11 mV and 296.29 mV, respectively, which is significantly higher than that of Fe _0.5M /NM-S1 _0.2M (228.43 mV@10 mA cm ^-2 and 257.12 mV@50 mA cm ^-2 ). When the current density is 100 mA cm ^-2 , the overpotential of Fe _0.5M /NM-S1 _0.2M -a is 315.62 mV, and the overpotential required is about 1.15 times that of Fe _0.5M /NM-S1 _0.2M .

The performance tests were conducted on the metal sulfide Fe _x /NM-S1 _y (5-1) catalytic material using ferric chloride as the iron source and the metal sulfide Fe1 _x /NM-S1 _y (5-2) catalytic material using ferric sulfate as the iron source in Example 5.

The test process is the same as above, and CV, LSV, EIS and i-t tests are performed. The test results are shown in Figures 13 and 14.

Figure 13 shows the LSV polarization curves of Fe _x /NM-S1 _y and Fe1 _x /NM-S1 _y . No obvious difference can be seen from the figure.

Figure 14 is the overpotential diagram of Fe _x /NM-S1 _y and Fe1 _x /NM-S1 _y . Figure 14 shows that the overpotential of Fe1 _0.5M /NM-S1 _0.2M at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 is 239.98 mV and 266.86 mV, respectively, which is almost the same as the catalytic performance of Fe _0.5M /NM-S1 _0.2M .

13-14 further show that more importantly, in the ethanol combustion method, even when the samples are treated with different iron salts, OER catalytic materials with higher catalytic activity are obtained.

The performance tests were conducted using the metal sulfide Fe _x /NF-S1 _y catalytic materials (6-1 to 6-4) in Example 6, the metal oxide Fe _0.5M /NF catalytic material (6-5) and the commercial nickel-based NF (6-6).

The test process is the same as above, and CV, LSV, EIS and i-t tests are performed. The test results are shown in Figures 15 to 17.

Figure 15 shows the LSV polarization curve of Fe _x /NF-S1 _y . It can be seen from the figure that Fe _0.5M /NF-S1 _0.2M has better OER performance.

Figure 16 is the overpotential diagram of Fe _x /NF-S1 _y . Figure 16 shows that the overpotential of Fe _0.5M /NF-S1 _0.2M at current densities of 10 mA cm ^-2 and 50 mA cm ^-2 is 244.19 mV and 269.66 mV, respectively, which is better than commercial nickel foam NF (400.49 mV and 561.31 mV).

Figure 17 is a constant potential polarization curve of Fe _0.5M /NF-S1 _0.2M . At a current density of 0.5 A cm ^-2 , Fe _0.5M /NF-S1 _0.2M can operate stably for at least 500 hours.

Figures 15-17 show that the ethanol combustion method can be applied to different commercial metal substrate support materials to obtain OER catalytic materials with stable performance and high catalytic activity.

In summary, Figures 1-17 prove that the rapid combustion method (taking ethanol as an example) is a synthetic method with wide adaptability. The present invention makes full use of the rapid ethanol combustion method to successfully incorporate different sulfur sources (potassium thiocyanate, yellow amide) into commercial metal substrates, and form a stable, highly catalytically active metal sulfide active phase. In addition, some metal salts (such as tungstates, etc.) can also be incorporated into the surface of commercial metal substrates using this method to form a multi-component metal oxide active phase. Finally, this method can be applied to a variety of self-supporting metal materials, such as the commercial nickel foam substrate mentioned in Example 6.

2. Microstructure and chemical properties

Taking the metal sulfide (Fe _x /NM-S1 _y ) catalytic materials (1-1 to 1-3) in Example 1 as an example, the microstructure and chemical properties thereof were analyzed, and the specific results are shown in FIGS. 18-20 .

Figure 18 is a SEM image of Fe _x /NM-S1 _y . The honeycomb skeleton of the original commercial nickel-molybdenum substrate (NM) and the catalyst Fe _0.5M /NM is distributed with smooth nanospheres (Figure 18 a, b). After sulfidation (Fe _0.5M /NM-S1 _0.2M ), the originally smooth surface of the nanospheres (diameter is about 0.51-3.47 μm) is occupied by tiny transition metal sulfide particles (diameter is about 160-280 nm) and becomes rough (Figure 18 c). The honeycomb skeleton of Fe _0.5M /NM-S1 _0.2M is still intact after the stability test (Figure 18 d).

Figure 19 shows the TEM (Transmission Electron Microscope) and SAED (Selected area electron diffraction) spectra of Fe _0.5M /NM-S1 _0.2M catalytic materials. The microstructure of the catalytic material was observed. Through high-resolution transmission electron microscopy analysis, four different lattice spacings were observed on the base plane: 0.269 nm (Fe ₂ O ₃ ), 0.265 nm (Fe ₂ O ₃ ), 0.312 nm (FeS), and 0.240 nm (NiO). Three different diffraction rings were observed in the SAED spectrum (Figure 19 g), corresponding to the (215) crystal plane of FeS, the (012) crystal plane of NiO, and the (1010) crystal plane of Fe ₂ O ₃ . This information shows that the ethanol combustion method successfully introduced the sulfur source into the catalytic material.

Figure 20 is an elemental mapping map of the Fe _0.5M /NM-S1 _0.2M catalytic material. It can be seen from the figure that Ni, Fe, Mo, S, and N elements are evenly distributed on the surface of the material, reflecting that a new Fe/NiMo-S complex is formed in the entire NM.

The above analysis shows that the rapid combustion method provided by the present invention can not only quickly sulfurize the surfaces of various commercial metal foams, but also incorporate some metal salts into the commercial metal foams to form a unique nanosphere array structure and exhibit excellent and stable electrochemical oxygen evolution performance.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims (10)

1. A self-supporting metal sulfide nanocatalytic material, characterized in that metal sulfide-modified nanospheres are distributed on the surface of a metal substrate; The catalytic material is obtained by soaking a metal substrate in a treatment liquid and then burning it with a flame; the soaking liquid includes a combustible solvent, an iron source, and a load source; the load source includes a sulfur source and/or a tungsten source. 2. The self-supporting metal sulfide nanocatalytic material according to claim 1, characterized in that the diameter of the nanosphere is 0.51-3.47 μm, the metal sulfide exists in the form of nanoparticles, and the diameter of the nanoparticles is 160-280 nm. 3. The self-supporting metal sulfide nanocatalytic material according to claim 1, characterized in that the gap between adjacent nanospheres is 0.7-1.7 μm. 4. The self-supporting metal sulfide nanocatalytic material according to claim 1, characterized in that the surface of the nanospheres is rich in hierarchical mesoporous structure. 5. The self-supporting metal sulfide nanocatalytic material according to claim 1 is characterized in that the metal substrate comprises at least one of nickel-molybdenum foam, nickel foam, iron foam, aluminum foam, titanium foam, cobalt foam, steel foam, and copper foam. 6. The self-supporting metal sulfide nanocatalytic material according to any one of claims 1 to 5, characterized in that the load source and the iron source can be dissolved in a combustible solvent; and the soaking liquid comprises at least one of the characteristics (1-1) to (1-5): (1-1) The iron source includes at least one of ferric chloride, ferric sulfate and ferric nitrate; (1-2) The loading source includes a sulfur source, and the sulfur source includes at least one of potassium thiocyanate and sulfonamide; (1-3) The load source includes a tungsten source, and the tungsten source includes sodium tungstate; (1-4) The load source includes a sulfur source and a tungsten source; (1-5) Flammable solvents include lower alcohols. 7. The self-supporting metal sulfide nanocatalytic material according to claim 6, characterized in that the lower alcohol comprises at least one of methanol, ethanol, n-propanol, isopropanol, and propenol. 8. The self-supporting metal sulfide nanocatalytic material according to claim 6, characterized in that when the loading source is a sulfur source, the ratio of the sulfur source, the iron source, and the lower alcohol is 0-0.4 mol/L:0-0.5 mol/L:10 mL. 9. The self-supporting metal sulfide nanocatalytic material according to claim 6, characterized in that when the loading source is a tungsten source, the ratio of the tungsten source, the iron source, and the lower alcohol is 0-5 g: 0-0.5 mol/L: 10 mL. 10. Use of the self-supporting metal sulfide nanocatalytic material according to any one of claims 1 to 9 in hydrogen production by electrolysis.