CN114671472A

CN114671472A - Preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis

Info

Publication number: CN114671472A
Application number: CN202210351888.8A
Authority: CN
Inventors: 李军山; 田晰; 李露明
Original assignee: Chengdu University
Current assignee: Chengdu University
Priority date: 2022-04-02
Filing date: 2022-04-02
Publication date: 2022-06-28
Anticipated expiration: 2042-04-02
Also published as: CN114671472B

Abstract

The invention provides a preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis, which comprises the following steps: (1) preparing nickel-sulfur slurry: mixing a nickel simple substance and sulfur powder in a ratio of 1:1 mol ratio is added into a container, and then ethylenediamine and ethanedithiol are sequentially added into the container to obtain a mixed solution; (2) solvent evaporation: filtering insoluble particles in the mixed solution obtained in the step (1) to obtain slurry; preheating a three-neck flask, and adding the slurry; then keeping the temperature of the three-neck flask to obtain dry powder; then grinding the dry powder into fine powder; (3) powder annealing: annealing the fine powder collected in the step (2) under inert gas. The nickel sulfide nano-particles prepared by the method solve the technical problems of low yield and low Faraday effect of the nickel-based non-noble metal used as an electrocatalyst for preparing formic acid.

Description

Preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis

Technical Field

The invention belongs to the field of new energy materials, and particularly relates to a preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis.

Background

At present, the world economy mainly depends on non-renewable petroleum resources to operate, carbon-based compounds related to the world are the most important chemical products in the world, but partial metabolites of the carbon-based compounds can cause serious pollution to the ecological environment. Therefore, the sustainable and efficient utilization, conversion and storage of other renewable energy sources rich in carbon content is one of the effective alternatives. Among them, the electrocatalytic conversion of biomass-derived chemicals is adopted to achieve this goal, opening up the way. In this global industrial transformation, as one of carbon cycle economy, C1 organic small molecules represented by formic acid, methanol and the like play a variety of important roles including raw materials, intermediates, platform compounds.

Formic acid is a colorless, pungent liquid, highly acidic, corrosive, and capable of stimulating skin blistering. Formic acid is used in rubber, pharmaceutical, dye, leather-like industries. Meanwhile, formic acid is also an organic chemical raw material and is also used as a disinfectant and a preservative. In nature, formic acid is present in the secretions of bees, certain ants and caterpillars. In conventional industrial processes, some formic acid is produced as a by-product in the production of other chemicals, particularly acetic acid, but such production is far from satisfying the current demand for formic acid.

In industry, formic acid is generally prepared at high temperature and high pressure. Under the action of strong alkali, methanol reacts with carbon monoxide to generate methyl formate:

CH₃OH+CO→HCOOCH₃

secondly, the base used is sodium methoxide, and methyl formate is hydrolyzed to obtain formic acid.

HCOOCH₃+H₂O→HCOOH+CH₃OH

Hydrolysis of methyl formate requires a large amount of water to ensure that the reaction proceeds smoothly. In commercial production, the reaction is carried out in a liquid state and under pressure, typical reaction conditions being 80 degrees celsius and 40 atmospheres.

In addition, some manufacturers use an indirect hydrolysis route, i.e., methyl formate is first reacted with ammonia to produce formamide, which is then hydrolyzed with sulfuric acid to give formic acid:

HCOOCH₃+NH₃→HCONH₂+CH₃OH

2HCONH₂+2H₂O+H₂SO₄→2HCOOH+(NH₄)₂SO₄

this technique has its own drawbacks, particularly in the handling of the by-product ammonium sulfate. Some manufacturers have recently developed an energy efficient process of extracting formic acid from large aqueous solutions for direct hydrolysis. In one of the processes (used by basf), formic acid is obtained by wet extraction under the action of an organic base.

In a laboratory preparation, formic acid can be obtained by heating oxalic acid in anhydrous glycerol, followed by steam distillation. Another preparation is the hydrolysis of isopropylnitrile with hydrochloric acid.

C₂H₅NC+2H₂O→C₂H₅NH₂+HCOOH

Preparation of isopropionitrile was obtained by reaction of ethylamine with chloroform. Notably, the unpleasant odor of isopropionitrile necessitates that the reaction be carried out in a fume hood.

Generally, the above industrial and experimental preparation of formic acid generally requires high temperature and high pressure or generates toxic and harmful gases, and thus, there is a strong need for a new method for preparing formic acid, particularly formic acid with high efficiency at normal temperature and pressure. Based on the advantages of electrochemistry, the intermittent characteristics of sustainable energy sources such as solar energy, wind energy and the like are utilized to the maximum extent, and surplus energy sources are converted into common chemicals, so that the dependence on fossil resources can be reduced, the industrial cost and the reaction condition of corresponding carbon-based chemical products are reduced, and the method is one of the priority roads for the sustainable development of future energy sources.

The nickel sulfide NiS has higher metal conductivity, good electrocatalytic activity and good chemical stability, and is a very promising electrocatalyst. CN113802139A discloses a nickel sulfide base electrocatalytic material with a core-shell structure and a preparation method thereof: uniformly dispersing nickel chloride hexahydrate, urea and ammonium fluoride in water to obtain a solution A, and drying the foamed nickel after ultrasonic cleaning to obtain treated foamed nickel; reacting the treated foam nickel with the solution AThen naturally cooling to obtain reacted foam nickel, and cleaning and drying the reacted foam nickel to obtain a precursor; uniformly dispersing ammonium metavanadate and thioacetamide in water to obtain a solution B; reacting the precursor with the solution B, and naturally cooling to obtain the amorphous VOx-coated Ni₃S₂The product is washed and dried to prepare the nickel sulfide base electrocatalysis material with the core-shell structure. The method improves the stability of nickel sulfide as an electrocatalyst. However, the research on the application of the non-noble metal-based catalyst to the electrocatalysis of methanol is less, and the invention aims to realize the high-efficiency conversion of the electrocatalysis of methanol to formic acid on the basis of cheap materials.

Disclosure of Invention

The invention aims to provide a preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis, and aims to solve the technical problems of low yield and low Faraday efficiency of preparing formic acid by taking a nickel-based non-noble metal as an electrocatalyst.

In order to solve the technical problems, the specific technical scheme of the preparation method of the nickel sulfide nano particles for preparing the formic acid by electrocatalysis is as follows:

a preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis comprises the following steps:

(1) preparing nickel-sulfur slurry: mixing a nickel simple substance and sulfur powder in a ratio of 1: weighing at a molar ratio of 1, adding the weighed materials into a container, and sequentially adding ethylenediamine and ethanedithiol into the container to obtain a mixed solution; stirring the mixed solution;

(2) solvent evaporation: filtering insoluble particles in the mixed solution obtained in the step (1) by using polytetrafluoroethylene to obtain slurry; preheating a three-neck flask, and adding the slurry; argon is introduced into the three-neck flask from one neck of the flask, and the other neck is connected with vacuum so as to rapidly remove steam in the slurry; placing a safety flask between the vacuum and the other neck to collect the vapors emanating from the slurry; then keeping the temperature of the three-neck flask to obtain dry powder; then grinding the dry powder into fine powder, and carrying out subsequent annealing treatment;

(3) powder annealing: and (3) annealing the fine powder collected in the step (2) under inert gas to obtain nickel sulfide nano particles.

Further, in the step (1), the volume ratio of the ethylenediamine to the ethanedithiol is 3.3: 0.3.

further, in the step (1), the stirring conditions are as follows: stirring was carried out at 750 rpm for 24 hours at room temperature.

Further, in the step (2), the polytetrafluoroethylene has a diameter of 0.45 μm.

Further, in the step (2), the temperature of the preheating of the three-neck flask is 250 ℃.

Further, in the step (2), the three-neck flask is kept at the temperature for 10 minutes.

Further, in the step (3), the annealing conditions are: and placing the fine powder in a tubular furnace at 300 ℃ under an argon atmosphere for 1 hour, heating at the speed of 3 ℃/min, and then preserving the heat at 400 ℃ for 30 minutes to obtain the nickel sulfide nanoparticles.

The preparation method of the nickel sulfide nano-particles for preparing the formic acid by electrocatalysis has the following advantages: the electrocatalytic performance of the metal electrode is far higher than the reference value of a single metal nickel electrode, so that the yield of formic acid is greatly improved; the simple material synthesis method and the low-cost formic acid synthesis method under normal temperature and normal pressure have wide prospects in sustainable energy and environment application.

Drawings

FIG. 1 is a schematic representation of the present invention: (a) x-ray diffraction pattern of nickel sulfide nanoparticles; (b) TEM images of nickel sulfide nanoparticles and their size distribution; (c) an X-ray diffraction pattern of elemental Ni nanoparticles; (d) TEM image of Ni elemental nanoparticles and their size distribution;

FIG. 2 is a graph of the topographical characterization of nickel sulfide nanoparticles of the present invention: (a) high power electron microscope picture and element distribution of nickel sulfide nano particles; (b) a diffraction pattern and schematic representation of the nickel sulfide nanoparticle crystal structure; (c) SEM image of nickel sulfide nanoparticles; (d) EDS element distribution diagram of nickel sulfide nano particles;

FIG. 3 is a comparison graph of voltammetric cycling curves for nickel sulfide nanoparticle-based electrodes of the invention (a) Ni elemental nanoparticle-based electrodes (b) in the absence (dashed line) or presence of 1 mole per liter of methanol in 1 mole per liter of KOH lye (solid line); note: the current density (J) is calculated from the measured current (i) divided by the geometric area of the glassy carbon electrode (0.196 square centimeters);

FIG. 4 shows the non-faradaic range of electrochemical activity of nickel sulfide nanoparticle-based electrodes (a-b) and Ni elemental nanoparticle-based electrodes (c-d) of the present invention in 1M KOH: (a, c) 1 to 100mV s^-1The CV curve is within the potential range of 0.9-1.0V under different scanning speeds; (b, d) Positive and negative sweeps are a linear fit function of current at 0.95V versus scan rate.

FIG. 5 shows the faradaic (0.9-1.6V) range electrochemical activity of nickel sulfide nanoparticle-based electrodes (a-c) and Ni elemental nanoparticle-based electrodes (d-f) in 1 mol/L KOH of the present invention: (a, d) CV curves at different scan rates; (b, e) the peak oxidation-reduction current and the scan rate are in the range of 10 to 50mV s^-1Linear fit between (c, f) the square root of the redox peak current and the scan rate is between 60 and 100mV s^-1A linear fit therebetween;

figure 6 shows the stability test and faraday efficiency of nickel sulfide nanoparticle-based electrodes and Ni elemental nanoparticle-based electrodes of the present invention: (a) testing the stability of the nickel sulfide nanoparticle-based electrode and the Ni elementary substance nanoparticle-based electrode under the external applied voltage of 1.6V in 1 mol/L KOH and mol/L methanol solution, wherein the testing time is 10000 seconds; (b) ion chromatography curve of the solution at the end of the stability test; (c) faradaic efficiencies of nickel sulfide nanoparticle-based electrodes and Ni elemental nanoparticle-based electrodes.

Detailed Description

In order to better understand the purpose, structure and function of the present invention, the following describes in detail the preparation method of nickel sulfide nanoparticles for preparing formic acid by electrocatalysis and the promotion of electrocatalysis activity thereof, based on the comparison with elemental metallic nickel electrocatalysis material, with reference to the accompanying drawings.

Based on the method, the inventor adopts cheap metal as raw material and synthesizes NiS nano material with precise control. The NiS nano-particles are divided into 3 steps.

First, i) a nickel-sulfur slurry is prepared. Mixing a nickel simple substance and sulfur powder in a ratio of 1:1 molar ratio (2 mmol total) was weighed into a 10 ml glass vial, and 3.3 ml of ethylenediamine and 0.3 ml of ethanedithiol were added to the vial in that order. The mixture was stirred at 750 rpm for 24 hours at room temperature. Stirring for a long time to fully mix the nickel simple substance and the sulfur powder to form uniform precursor slurry.

Secondly, ii) the solvent is evaporated. The insoluble particles were filtered with teflon of 0.45 micron diameter (nickel simple substance and sulfur powder of large particle size, which were not sufficiently dissolved, were filtered out to obtain nanoparticles free of nickel and simple substance by reuse), and left in the filter flask for use. Argon was passed into the flask from one neck of the three-necked flask, while the other neck was connected to a vacuum to rapidly remove the vapor from the slurry. A safety flask containing water/ethanol was placed between the vacuum and the reaction flask to collect the vapors emanating from the slurry solution. After the flask was preheated to 250 ℃, the slurry was added by syringe and the temperature of the three-necked flask was first decreased and then slowly increased to 250 ℃. And then keeping the temperature of the flask for about 10 minutes to obtain dry powder, and obtaining the nano particles with uniform appearance at the temperature, thereby obtaining high-efficiency and stable electro-catalytic activity. Then grinding the product into fine powder and carrying out subsequent annealing treatment.

Finally, iii) annealing the powder. Placing the collected fine powder in a tubular furnace at 300 ℃ under argon atmosphere for 1 hour, heating at the speed of 3 ℃/min, and then preserving the heat at 400 ℃ for 30 minutes to finally obtain the nickel sulfide nano-particles. Annealing under the protection of inert atmosphere can prevent the formation of oxide on one hand and can improve the crystallinity of the nano-particles on the other hand.

For comparison, the inventors prepared Ni elemental nanoparticles of the same diameter by the following method: a three-necked flask was charged with a magnetic rod, 1 mmol of nickel acetylacetonate, 2.7 ml of oleylamine, 0.4 mmol of n-trioctylphosphine and 0.25 mmol of n-trioctylphosphine oxide, and the flask was kept at 130 ℃ for 30 minutes and then purged with argon. The flask was then rapidly heated to 215 ℃ and held at this temperature for 45 minutes. Subsequently, the flask was cooled to room temperature using a water bath. Adding ethanol, and centrifuging to separate black precipitate. To further remove surface residual ligands, the precipitate was dispersed in a mixture containing 28 ml acetonitrile and 0.8 ml hydrazine hydrate and stirred for about 2 hours before testing electrochemical performance. After centrifugation, the cells were washed 3 times with acetonitrile. Finally, drying under vacuum for later use.

As shown in FIG. 1a, the X-ray diffraction pattern of the nickel sulfide nanoparticles shows that they have a nickel sulfide phase (JCPDS No. 01-075-0613). TEM characterization showed that the resulting particles had an average diameter of about 12 nm (FIG. 1 b). The nanoparticles of elemental Ni as a comparative reference correspond to the crystalline phase of elemental Ni (FIG. 1c, JCPDS No. 03-065-.

FIG. 2 demonstrates that the synthesized nickel sulfide nanoparticles have uniform element components and excellent crystal structure, and provide possibility for serving as a high-performance catalyst. The EELS chemical composition diagram shown in fig. 2a shows a uniform distribution of Ni and S. As shown in fig. 2b, HRTEM showed that the nanoparticles had good crystallinity, conforming to NiS hexagonal phase (space group P63/mmc), with unit cell size of

SEM-EDS analysis showed a Ni to S atomic ratio of 1:1, as shown in FIG. 2c, FIG. 2 d.

Electrocatalysis experiments are generally carried out by adopting a three-electrode system to test the methanol oxidation property: the glassy carbon electrode is a working electrode, the Pt wire is a counter electrode, and Hg/HgO is a reference electrode. Prior to testing the electrochemical properties, an electrocatalyst ink needs to be formulated. 5 mg of a sample (nickel sulfide nanoparticles as a high-efficiency electro-catalytic material; Ni elementary nanoparticles as a comparative material) and 10 mg of carbon black were dissolved in 1 ml of water, 1 ml of ethanol and 0.1 ml of Nafion, and ultrasonically stirred for 1 hour. 5 microliter of the newly prepared electrocatalyst slurry is taken by a pipette and dripped on a glassy carbon electrode with the diameter of 5 millimeters to respectively obtain a Ni simple substance nanoparticle-based electrode and a nickel sulfide nanoparticle-based electrode. And after the sample is naturally dried, connecting the sample serving as a working electrode to a direct electrochemical workstation for test analysis. For comparison, the applied voltage (vs. Hg/HgO) was converted to a reversible hydrogen electrode potential according to the following nernst equation:

E_RHE＝E_Hg/HgO+0.059×pH+E^θ _Hg/HgO

wherein E is_Hg/HgOFor applying a voltage, E^θ _Hg/HgOIs the potential of the reference electrode (0.098V) and a 1M KOH solution at pH corresponds to the actual valence (13.6 measured with a pH meter).

The method adopts a Ni simple substance nano-particle-based electrode, a nickel sulfide nano-particle-based electrode, a KOH solution with the concentration of electrolytic liquid of 1 mol/L and a methanol solution with the concentration of 1 mol/L. As shown by the dotted line in fig. 3, when methanol was not added, the current density sharply increased at about 1.342V, forming an oxidation peak of NiOOH, and then at about 1.65V, the current density again increased, mainly due to the generation of oxygen. On the other hand, in the presence of 1 mole/liter of methanol, the current density began to increase at about 1.311V, mainly due to the current provided by the methanol electrooxidation. Under the condition that the relative standard hydrogen electrode potential is 1.6V, the electrocatalytic performance of the nickel sulfide nano-particle-based electrode is 121.2mA cm^-2As shown in fig. 3 a; 56.8mA cm larger than Ni simple substance nano-particle-based electrode^-2As in fig. 3 b. Generally speaking, the oxidation of methanol to formic acid can be generally divided into the following four steps: (1) generating NiOOH active substances; (2) adsorbing methanol; (3) dehydrogenating methanol into formaldehyde; (4) further oxidation of formaldehyde to formic acid:

(1)OH^-+Ni(OH)₂→NiOOH+H₂O+e-

(2)CH₃OH_sol.→CH₃OH_ads.

(3)CH₃OH_ads.+NiOOH→C*H₂OH+Ni(OH)₂

(4)C*H₂OH+3NiOOH+OH^-→CHOO^-+3Ni(OH)₂

the overall reaction at the positive electrode occurs as follows:

CH₃OH+5OH^-→HCOO^-+4H₂O+4e^-

meanwhile, hydrogen evolution reaction is carried out in the negative electrode:

2H₂O+2e^-→2OH^-+H₂

improving intrinsic parameters of the single metal material, such as: electrochemical active surface areas (ECSA) and active site coverage areas (Γ)^*) And the diffusion coefficient (D) thereof, etc. can improve the properties of the electrocatalytic material. On one hand, the material is in a nanometer size range, and the specific surface can be greatly increased, so that the catalytic active sites are increased; on the other hand, the electronic structure can be effectively changed by adopting the hybridization of single metal, so that the intrinsic characteristics of the electrocatalyst are improved. The invention respectively explains the improvement of the nickel sulfide nanoparticles on the electrocatalytic activity from the electrochemical activity area (ECSA), the active site coverage area and the diffusion coefficient.

Electrochemical active area (ECSA):

under alkaline conditions, NiOOH active species formation is decisive for the electrochemical performance of methanol oxidation, and the intrinsic parameters associated therewith are: electrochemically active surface area (ECSA), active site coverage area of redox species, diffusion coefficient, and the like. First, the CV curve and electrochemical double layer capacitance (C) at different scan rates over the non-Faraday potential range 0.9-1.0V vs. RHE (FIG. 4a) were used_dl) The electrochemically active surface area (ECSA) can be estimated as shown in figure 4 b. Plotting the capacitance current (i) between the current at 0.95V and the scan rate (V) yields a slope equal to C_dlStraight line (fig. 4 b).

ECSA＝C_dl/C_s

By formula, as shown in FIG. 4C and FIG. 4d, with C_dlDivided by the specific capacitance (C)_s0.04) calculated Nickel sulfide ECSA of 6.4cm²5.5cm higher than that of nickel²。

Active site coverage area:

at 10 to 100mV s^-1The inventors compared CV curves of nickel sulfide nanoparticle-based electrodes and Ni elemental nanoparticle-based electrodes in the faradaic range at the scan rate of (a). As shown in fig. 5a and figAnd 5d, along with the increase of the scanning speed, the positive electrode peak positions of the nickel sulfide nano-particle-based electrode and the Ni elementary substance nano-particle-based electrode move towards the direction with high electric potential, and the negative electrode peak positions move towards the direction with low electric potential. Peak current (I) of positive and negative electrodes_pc,I_pa) Both increase linearly with increasing scanning speed (fig. 5b and 5 e). Peak Current (I) to obtain accurate active site coverage_p) Taking the peak current (I) of positive and negative electrodes_pc,I_pa) Average value of (a). From the average slope of the positive and negative peak currents with the scan speed, the active site coverage area (Γ) can be calculated by the following equation^*)：

Wherein n, F, R, T and A are the number of transferred electrons (in this case n ═ 1), and the Faraday constant (96845C mol)^-1) Gas constant (8.314J K)^-1mol^-1) Temperature and geometric surface area of glassy carbon electrode (0.196 cm)²). From the above equation, the active site coverage area (Γ) of the nickel sulfide nanoparticle-based electrode (fig. 5b) can be calculated^*) Is 1.48X 10^-6mol cm^-21.61X 10 higher than Ni elemental nanoparticle-based electrode (FIG. 5e)^-7mol cm^-2An order of magnitude.

Diffusion coefficient:

the electrochemical properties are not only related to the area covered by NiOOH active sites, but also to their diffusion coefficient, and it is generally believed that diffusion of active species is a key process that limits the rate of reaction. As shown in fig. 5c and 5f, peak current (I) of nickel sulfide nanoparticle-based electrode and Ni elemental nanoparticle-based electrode_pc,I_pa) A straight line can be fitted to the square root of the scan rate, and the diffusion coefficient can be calculated using the following equation:

I_p＝2.69×10⁵n^3/2AD^1/2Cv^1/2

wherein n, a, C and υ are the number of transferred electrons (in this case, n ═ 1), and the geometric surface area of the glassy carbon electrode (in this case)0.196cm²) Proton concentration and scan rate. Wherein, according to the related literature, C is an estimated proton concentration of 3.97g cm^-3. To obtain an accurate diffusion coefficient, the peak current (I)_p) Taking the peak current (I) of positive and negative electrodes_pc,I_pa) Average value of (a). Using the above equation, the rate-limiting diffusion coefficient of the Ni elemental nanoparticle-based electrode of 3.13X 10 can be calculated^-7cm² s^-1(FIG. 5f), a rate limiting diffusion coefficient of 3.78X 10 slightly lower than that of nickel sulfide nanoparticle-based electrodes^-7cm² s^-1(FIG. 5 c).

To test the electrochemical stability of the catalyst, the inventors performed a long cycle chronoamperometric stability test of 10000 seconds in a 1 mol/l KOH solution and 1 mol/l methanol. As can be seen from FIG. 6a, the current densities of the two electrodes decrease faster in the first few minutes and then tend to be stable, and after reaction for 10000s, the current densities of methanol oxidation on the nickel sulfide nanoparticle-based electrode and the Ni elemental nanoparticle-based electrode are 82.9 mA and 45.1mA cm respectively^-2。

To calculate formic acid production and faraday efficiency for methanol oxidation, the solution is typically calibrated. First, 0.5 ml of the stability-tested solution was diluted in 8 ml of purified water and then tested by ion chromatography. As shown in fig. 6b, the upward peak at 4.8 minutes corresponds to formic acid. Under the test condition of 10000 seconds and 1.6V, 0.45 millimole of formic acid is electrochemically generated on the nickel sulfide nanoparticle-based electrode, and the generation amount of the formic acid is higher than 0.27 millimole of the formic acid on the Ni simple substance nanoparticle-based electrode. In addition, the faradaic efficiency of methanol oxidation under these conditions can be calculated using the faradaic efficiency equation:

wherein n is the number of electron transfers (4 electron transfers in total for the conversion of methanol to formic acid), and F is the Faraday constant (96485C mol)^-1). By calculation, the nickel sulfide nanoparticle-based electrode has higher faradaic efficiency than the oxidation of methanol to formic acid of the Ni elemental nanoparticle-based electrode, which is 98 respectively1% and 96.6%, as shown in fig. 6 c.

In summary, the inventors provide a method for preparing nickel sulfide nanoparticles for electrocatalytic preparation of formic acid. The electrocatalytic performance of the electrode on methanol oxidation is researched in an alkaline medium, and the test result is far higher than the reference value of the Ni elementary substance nano-particle-based electrode. Although the introduction of sulfur does not improve the Faraday efficiency of formic acid, the production of chemicals is greatly improved, the yield of the formic acid of the nickel sulfide nanoparticle-based electrode is 0.17 millimole/hour, and the formic acid is almost Ni simple substanceSodium (A)Twice the yield of rice grain-based electrodes.

It is to be understood that the present invention has been described with reference to certain embodiments, and that various changes in the features and embodiments, or equivalent substitutions may be made therein by those skilled in the art without departing from the spirit and scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A preparation method of nickel sulfide nanoparticles for preparing formic acid through electrocatalysis is characterized by comprising the following steps:

(2) solvent evaporation: filtering insoluble particles in the mixed solution obtained in the step (1) by using polytetrafluoroethylene to obtain slurry; preheating a three-neck flask, and adding the slurry; argon is introduced into the three-neck flask from one neck of the flask, and the other neck is connected with vacuum so as to quickly remove steam in the slurry; placing a safety flask between the vacuum and the other neck to collect the vapors emanating from the slurry; then keeping the temperature of the three-neck flask to obtain dry powder; then grinding the dry powder into fine powder, and carrying out subsequent annealing treatment;

2. The method for preparing nickel sulfide nanoparticles for electrocatalytic preparation of formic acid according to claim 1, wherein in said step (1), the volume ratio of ethylenediamine to ethanedithiol is 3.3: 0.3.

3. the method for preparing nickel sulfide nanoparticles for electrocatalytic preparation of formic acid as set forth in claim 2, wherein in said step (1), the stirring conditions are: stirring was carried out at 750 rpm for 24 hours at room temperature.

4. The method for preparing nickel sulfide nanoparticles for electrocatalytic production of formic acid according to claim 3, wherein, in the step (2), the polytetrafluoroethylene has a diameter of 0.45 μm.

5. The method for preparing nickel sulfide nanoparticles for electrocatalytic production of formic acid according to claim 4, wherein the temperature of the three-necked flask is preheated to 250 ℃.

6. The method for preparing nickel sulfide nanoparticles for electrocatalytic production of formic acid according to claim 5, wherein the three-necked flask is maintained for a holding time of 10 minutes.

7. The method for preparing nickel sulfide nanoparticles for electrocatalytic production of formic acid as set forth in any one of claims 1 to 6, wherein in said step (3), annealing conditions are: and placing the fine powder in a tubular furnace at 300 ℃ under an argon atmosphere for 1 hour, heating at the speed of 3 ℃/min, and then preserving the heat at 400 ℃ for 30 minutes to obtain the nickel sulfide nanoparticles.