Multivalent high-entropy sulfide, preparation method thereof and application of multivalent high-entropy sulfide as electrocatalyst

Abstract

The invention discloses multivalent high-entropy sulfide, a preparation method thereof and application of the multivalent high-entropy sulfide as an electrocatalyst, and belongs to the technical field of high-entropy transition metal sulfide. The preparation method comprises the following steps: dissolving a plurality of metal nitrates in isopropanol and glycerol according to the concentration of equal molar ratio by adopting a solvothermal method, carrying out solvothermal reaction, filtering and washing to obtain a metal glycerol precursor; the method comprises the following steps: dissolving a metal glycerol precursor and thioacetamide in ethanol, carrying out solvothermal reaction, cooling, centrifuging, washing and drying to obtain the multivalent high-entropy sulfide. The multivalent high-entropy sulfide which is simple in synthesis method, stable in structure and easy in raw material obtaining is obtained and can serve as an electrocatalyst to be applied to electrocatalytic nitrate reduction synthesis of ammonia, and a foundation is laid for developing other high-entropy transition metal sulfide serving as an electrocatalyst for electrocatalytic nitrate wastewater synthesis of value-added chemicals.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of high-entropy transition metal sulfides, and particularly relates to a multi-valence high-entropy sulfide, a preparation method thereof and application of the multi-valence high-entropy sulfide as an electrocatalyst. BACKGROUND

[0002] The acceleration of industrialization and the expansion of agriculture have led to a steady increase in nitrate emissions in modern society, mainly due to the massive discharge of industrial wastewater and the overuse of chemical fertilizers in agricultural systems. Electrochemical reduction of nitrate is a particularly promising method and can selectively convert nitrate into ammonia. However, electrocatalytic NO3 - The reduction reaction is a complex 8-electron, 9-proton (NO3 - + 9H + + 8e - → NH3 + 3H2O) reaction process, involving multiple reaction pathways and intermediates, resulting in sluggish kinetics. Therefore, it is necessary to develop electrocatalysts with high selectivity and high activity. High-entropy materials (HEM) are composed of five or more metal elements in a near-equi-molar ratio (5-35 at%), which have attracted attention due to their severe lattice distortion, slow diffusion, cocktail effect and high-entropy effect. Compared with traditional non-noble metal catalysts, HEMCs have the advantages of multi-component synergy, lattice distortion, active site optimization and stable catalytic interface. SUMMARY

[0003] In order to solve the technical problems existing in the prior art, one of the purposes of the present application is to provide a multi-valence high-entropy sulfide with high catalytic efficiency. The second purpose of the present application is to provide a preparation method of a multi-valence high-entropy sulfide, which has easily available raw materials and simple preparation method. The third purpose of the present application is to provide the application of the multi-valence high-entropy sulfide as an electrocatalyst.

[0004] In order to achieve the above-mentioned purposes of the application, the first aspect of the present application provides a multi-valence high-entropy sulfide, and the preparation method comprises the following steps:

[0005] 1) Dissolve a plurality of metal nitrate salts in isopropyl alcohol and glycerol, transfer the obtained suspension into a Teflon-lined stainless steel autoclave, and perform a solvothermal reaction. After cooling, filtration, washing, a metal glycerol precursor is obtained; the plurality of metal nitrate salts are selected from five or six or seven of the metal nitrate salts of Fe, Co, Cu, Cr, Zr, Ni and Bi;

[0006] 2) Dissolve the metal glycerol precursor and thioacetamide in ethanol, stir for 30-40 min, transfer the obtained mixture into a Teflon-lined stainless steel autoclave, and perform a solvothermal reaction. After cooling, centrifugation, washing, drying, a multi-valence high-entropy sulfide is obtained.

[0007] Further, in step 1), each metal nitrate in the plurality of metal nitrates is added in an equimolar ratio.

[0008] Further, in step 1), the volume ratio of isopropyl alcohol to glycerol is (5-6):1.

[0009] Further, in step 1), the solvothermal reaction is heating at a temperature of 145-155°C for 10-12 hours.

[0010] Further, in step 2), the mass ratio of the metal glycerol precursor to thioacetamide is 100:(160-170).

[0011] Further, in step 2), the solvothermal reaction is heating at a temperature of 155-165°C for 8-10 hours.

[0012] The second aspect of the present application provides a use of a multi-valence high-entropy sulfide as an electrocatalyst in the electrocatalytic reduction of nitrate to synthesize ammonia.

[0013] Further, the method is as follows: the multi-valence high-entropy sulfide is loaded on carbon cloth as a working electrode, the reference electrode is Ag / AgCl, the counter electrode is a platinum sheet, the electrolyte is a 1.0M KOH solution and a 0.1M potassium nitrate solution, and the reduction of nitrate to synthesize ammonia is catalyzed.

[0014] The third aspect of the present application provides a use of a multi-valence high-entropy sulfide as an electrocatalyst in the electrocatalytic reduction of nitrate to synthesize ammonia in a Zn-NO3 - battery.

[0015] Further, the method is as follows: the multi-valence high-entropy sulfide is loaded on carbon cloth as a cathode working electrode, a zinc sheet is used as an anode working electrode, the cathode electrolyte is a 1.0M KOH solution and a 0.1M potassium nitrate solution, and the anode electrolyte is a 1.0M KOH solution.

[0016] The beneficial effects of the present application are:

[0017] 1. The multi-valence high-entropy sulfide provided by the present application has high catalytic efficiency, and the catalytic activity of the seven-membered multi-valence high-entropy sulfide (F3CZNB) provided by the present application is higher than that of the six-membered multi-valence high-entropy sulfide (F3CZN) and the five-membered multi-valence high-entropy sulfide (F3CZ). As an electrocatalyst in the electrocatalytic reduction of nitrate to synthesize ammonia, the optimal NH3 yield is 5.67mg h -1 cm -2 (-0.8V vs. RHE), and the optimal FE is 92.3% (-0.6V vs. RHE), which lays a foundation for the electrocatalyst for the electrocatalytic synthesis of value-added chemicals from nitrate wastewater.

[0018] 2、The multivalent high-entropy sulfide, the seven-element multivalent high-entropy sulfide (F3CZNB) provided by the application is used as an electrocatalyst in Zn-NO3 - In the battery, a power density of 6.45 mW cm -2 may be generated at 0.66 V.

[0019] 3、The preparation method of the multivalent high-entropy sulfide provided by the application is simple and the raw materials are easy to obtain. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a synthesis diagram of the multivalent high-entropy sulfide.

[0021] Figure 2 is an XRD spectrum of F3CZNB, F3CZN and F3CZ prepared in Example 1.

[0022] Figure 3 is a scanning electron microscope image of F3CZNB prepared in Example 1.

[0023] Figure 4 is a high-angle annular dark-field image and an EDS surface scanning image of each element of F3CZNB prepared in Example 1.

[0024] Figure 5 is an ammonia yield comparison diagram (a) and a Faraday efficiency comparison diagram (b) of each catalyst in Example 2.

[0025] Figure 6 is a discharge curve and a corresponding energy density diagram of the F3CZNB electrocatalyst in Example 3.

[0026] Figure 7 is an open-circuit voltage diagram of F3CZNB in Example 3. DETAILED DESCRIPTION

[0027] Example 1 multivalent high-entropy sulfide

[0028] I. Seven-element multivalent high-entropy sulfide (F3CZNB)

[0029] The preparation method is as follows:

[0030] 1. Preparation of metal glycerol precursor:

[0031] Dissolve 0.5 mmol of iron nitrate (Fe(NO3)3-9H2O), 0.5 mmol of cobalt nitrate (Co(NO3)2-6H2O), 0.5 mmol of copper nitrate (Cu(NO3)2-3H2O), 0.5 mmol of chromium nitrate (Cr(NO3)3-9H2O), 0.5 mmol of zirconium nitrate (Zr(NO3)4-5H2O), 0.5 mmol of nickel nitrate (Ni(NO3)2-6H2O), and 0.5 mmol of bismuth nitrate (Bi(NO3)3-5H2O) in 34 mL of isopropyl alcohol and 6 mL of glycerol. Then transfer the resulting suspension into a Teflon-lined stainless steel autoclave and heat at 150 °C for 10 h, filter, wash, and obtain the metal glycerol precursor.

[0032] 2. Preparation of a seven-membered multi-valence high-entropy sulfide

[0033] Dissolve 100 mg of the metal glycerol precursor and 167 mg of thioacetamide in 50 mL of ethanol, stir for 30 min, then transfer the resulting mixture into a Teflon-lined stainless steel autoclave and heat at 160 °C for 8 h. After cooling, centrifuge, wash, and dry the resulting product to obtain a seven-membered multi-valence high-entropy sulfide, labeled as F3CZNB.

[0034] II. Preparation of a six-membered multi-valence high-entropy sulfide (F3CZN)

[0035] The preparation method is as follows:

[0036] 1. Preparation of a metal glycerol precursor:

[0037] Dissolve 0.5 mmol of iron nitrate (Fe(NO3)3-9H2O), 0.5 mmol of cobalt nitrate (Co(NO3)2-6H2O), 0.5 mmol of copper nitrate (Cu(NO3)2-3H2O), 0.5 mmol of chromium nitrate (Cr(NO3)3-9H2O), 0.5 mmol of zirconium nitrate (Zr(NO3)4-5H2O), and 0.5 mmol of nickel nitrate (Ni(NO3)2-6H2O) in 34 mL of isopropyl alcohol and 6 mL of glycerol. Then transfer the resulting suspension into a Teflon-lined stainless steel autoclave and heat at 150 °C for 10 h, filter, wash, and obtain the metal glycerol precursor.

[0038] 2. Preparation of a six-membered multi-valence high-entropy sulfide

[0039] Dissolve 100 mg of the metal glycerol precursor and 167 mg of thioacetamide in 50 mL of ethanol, stir for 30 min, then transfer the resulting mixture into a Teflon-lined stainless steel autoclave and heat at 160 °C for 8 h. After cooling, centrifuge, wash, and dry the resulting product to obtain a six-membered multi-valence high-entropy sulfide, labeled as F3CZN.

[0040] Three, five-element multivalent high-entropy sulfide (F3CZ)

[0041] The preparation method is as follows:

[0042] 1. Preparation of metal glycerol precursor:

[0043] Dissolve 0.5 mmol of iron nitrate (Fe(NO3)3·9H2O), 0.5 mmol of cobalt nitrate (Co(NO3)2·6H2O), 0.5 mmol of copper nitrate (Cu(NO3)2·3H2O), 0.5 mmol of chromium nitrate (Cr(NO3)3·9H2O), and 0.5 mmol of zirconium nitrate (Zr(NO3)4·5H2O) in 34 mL of isopropanol and 6 mL of glycerol. Then transfer the obtained suspension into a Teflon-lined stainless steel autoclave, heat at 150°C for 10 h, filter, wash, and obtain the metal glycerol precursor.

[0044] 2. Preparation of five-element multivalent high-entropy sulfide

[0045] Dissolve 100 mg of metal glycerol precursor and 167 mg of thioacetamide in 50 mL of ethanol, stir for 30 min, then transfer the obtained mixture into a Teflon-lined stainless steel autoclave, heat at 160°C for 8 h, after cooling, centrifuge, wash, and dry the obtained product to obtain the five-element multivalent high-entropy sulfide, marked as F3CZ.

[0046] Four, test results

[0047] Figure 2 is the XRD spectrum of F3CZNB, F3CZN, and F3CZ prepared in this example. X-ray diffraction (XRD) analysis shows that the synthesized five-, six-, and seven-element multivalent high-entropy sulfides (HEMCs) are consistent with the standard card ((Cu 0.4 Fe 0.6 )S2PDF#82-0234). With the increase of the number of metal elements, the peak intensity gradually decreases, and the peak width becomes obviously wider. The results show that the multivalent high-entropy sulfide promotes the random occupation of various metal atoms in the crystal lattice, breaks the long-range ordered structure, and forms severe lattice distortion and nanoscale grains (even amorphous). From the five-component F3CZ to the seven-component F3CZNB system, the crystal structure changes from semi-crystalline to amorphous, and the increase of entropy is positively correlated with the lattice disorder degree. This disorder is conducive to charge transfer and the adsorption of products at active sites.

[0048] Figure 3 is the scanning electron microscope image of F3CZNB prepared in this example. The morphology of the sample after sulfidation is a microsphere structure composed of aggregated nanoparticles.

[0049] Figure 4 are high-angle annular dark-field image and EDS mapping of F3CZNB prepared in this example. The image shows uniform distribution of Fe, Co, Cu, Cr, Zr, Ni, Bi and S. According to atomic percentage calculation from EDS spectrum, AS mix of F3CZNB is 1.70R (R is gas constant), which exceeds 1.61R, thus meeting the standard of high-entropy materials.

[0050] Example 2 Application of multi-valence high-entropy sulfide as electrocatalyst in electrocatalytic reduction of nitrate to synthesize ammonia

[0051] Method: The seven-membered multi-valence high-entropy sulfide F3CZNB, six-membered multi-valence high-entropy sulfide F3CZN and five-membered multi-valence high-entropy sulfide F3CZ prepared in Example 1 were respectively loaded on carbon cloth as working electrode as electrocatalyst, the reference electrode was Ag / AgCl, the counter electrode was platinum sheet, and the electrolyte was 1.0M KOH solution and 0.1M potassium nitrate solution.

[0052] Figure 5 is the performance of multi-valence high-entropy sulfide in electrochemical reduction of NO3 - by chronoamperometry at different potentials. As shown in a of Figure 5 , under the condition of -0.8 (V vs. RHE), the NH3 yield of F3CZNB was 5.67mg h -1 cm -2 , which was significantly higher than that of F3CZN (4.33mg h -1 cm -2 ) and F3CZ (4.04mg h -1 cm -2 ). As shown in b of Figure 5 , in the potential range of -0.4V vs. RHE ~ -0.8V vs. RHE, the NH3 Faraday efficiency (FE) of F3CZNB was significantly higher than that of other catalysts. The FE of F3CZNB reached as high as 92.3% under the condition of -0.6 (V vs. RHE), which was superior to that of F3CZN (75% under the condition of -0.6 (V vs. RHE)) and F3CZ (70.4% under the condition of -0.7 (V vs. RHE)).

[0053] Example 3 Application of seven-membered multi-valence high-entropy sulfide F3CZNB as electrocatalyst in Zn-NO3 - battery

[0054] Method: The seven-valence high-entropy sulfide F3CZNB prepared in Example 1 was loaded on carbon cloth as an electrocatalyst as a cathode working electrode, a zinc sheet as an anode working electrode, and a 1.0M KOH solution and a 0.1M potassium nitrate solution as a cathode electrolyte.

[0055] In view of the excellent catalytic activity of F3CZNB in the reduction of NO3 - , further practical applications were explored. For this purpose, a Zn-NO3 - fuel cell was assembled with a zinc sheet as the anode and F3CZNB catalyst as the cathode in an alkaline environment. During discharging, NO3 - reduction occurred at the cathode, and Zn dissociation occurred at the anode, and the reaction was 4Zn + 8OH - → 4ZnO + 4H2O + 8e - . Figure 6 The discharge curve of the Zn-NO3 - fuel cell with F3CZNB as the cathode catalyst and its corresponding energy density are shown. During discharging, the output current density gradually increased with the increase of negative voltage. The power density of the Zn-NO3 -2 fuel cell reached 6.45 mW cm - at 0.66 (V vs. Zn). Figure 7 The open-circuit voltage (OCV) of the Zn-NO3 - fuel cell with F3CZNB as the cathode catalyst was 1.285 V.

Claims

1. A multivalent high entropy sulfide, characterized in that: The preparation method of the multivalent high entropy sulfide comprises the following steps: 1) dissolving a plurality of metal nitrates in isopropyl alcohol and glycerol, transferring the resulting suspension to a Teflon-lined stainless steel autoclave for a solvothermal reaction, cooling, filtering, and washing to obtain a metal glycerol precursor; the plurality of metal nitrates are selected from five, six, or seven metal nitrates of Fe, Co, Cu, Cr, Zr, Ni, and Bi; 2) dissolving the metal glycerol precursor and thioacetamide in ethanol and stirring for 30-40 minutes, transferring the resulting mixture to a Teflon-lined stainless steel autoclave for a solvothermal reaction, cooling, centrifuging, washing, and drying to obtain a multivalent high-entropy sulfide.

2. The multivalent high entropy sulfide according to claim 1, characterized in that: In step 1), among the plurality of metal nitrates, each metal nitrate is added in an equimolar ratio.

3. The multivalent high entropy sulfide according to claim 1, characterized in that: In step 1), the volume ratio of isopropyl alcohol to glycerol is (5-6):

1.

4. The multivalent high entropy sulfide according to claim 1, characterized in that: In step 1), the solvent thermal reaction is carried out by heating at a temperature of 145° C. to 155° C. for 10 h to 12 h.

5. The multivalent high entropy sulfide according to claim 1, characterized in that: In step 2), the mass ratio of metal glycerol precursor: thioacetamide = 100: (160-170).

6. The multivalent high entropy sulfide according to claim 1, characterized in that: In step 2), the solvent thermal reaction is carried out by heating at a temperature of 155° C. to 165° C. for 8 h to 10 h.

7. Use of a multivalent high entropy sulfide according to any one of claims 1 to 6 as an electrocatalyst in electrocatalytic nitrate reduction to synthesize ammonia.

8. The use according to claim 7, characterized in that The method is as follows: multivalent high-entropy sulfide is loaded on carbon cloth as a working electrode, the reference electrode is Ag / AgCl, the counter electrode is a platinum sheet, the electrolyte is 1.0M KOH solution and 0.1M potassium nitrate solution, and catalyzes the reduction of nitrate to synthesize ammonia.

9. A multivalent high entropy sulfide as claimed in any one of claims 1 to 6 as an electrocatalyst in Zn-NO3 - Application in batteries.

10. The use according to claim 9, characterized in that The method is as follows: multivalent high-entropy sulfide is loaded on carbon cloth as a cathode working electrode, a zinc sheet is used as an anode working electrode, the cathode electrolyte is 1.0M KOH solution and 0.1M potassium nitrate solution, and the anode electrolyte is 1.0M KOH solution.

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