CN115161667A - Electrocatalytic material alkylthiol-VS for ENRR 2 Preparation method of (1) - Google Patents

Electrocatalytic material alkylthiol-VS for ENRR 2 Preparation method of (1) Download PDF

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CN115161667A
CN115161667A CN202210807086.3A CN202210807086A CN115161667A CN 115161667 A CN115161667 A CN 115161667A CN 202210807086 A CN202210807086 A CN 202210807086A CN 115161667 A CN115161667 A CN 115161667A
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alkyl mercaptan
carbon paper
enrr
solution
ethanol
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严乙铭
迟新月
王晓璇
熊媛媛
李书源
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Beijing University of Chemical Technology
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    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/27—Ammonia
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
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    • C25B11/04—Electrodes; Manufacture thereof not otherwise provided for characterised by the material
    • C25B11/051—Electrodes formed of electrocatalysts on a substrate or carrier
    • C25B11/073—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material
    • C25B11/091—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds
    • C25B11/095—Electrodes formed of electrocatalysts on a substrate or carrier characterised by the electrocatalyst material consisting of at least one catalytic element and at least one catalytic compound; consisting of two or more catalytic elements or catalytic compounds at least one of the compounds being organic
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    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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    • Y02E60/30—Hydrogen technology
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Abstract

Electrocatalytic material alkylthiol-VS for ENRR 2 Belonging to the field of electrocatalysis nitrogen fixation. The method comprises the steps of mixing vanadium disulfide raw materials and heating water, loading a vanadium disulfide material on carbon paper, and soaking the loaded carbon paper in alkyl mercaptan to synthesize a working electrode. The invention is mainly used for preparing alkyl mercaptan-VS 2 The electrocatalytic nitrogen fixation material solves VS 2 The catalyst is used for solving the problem of poor ENRR selectivity. Wherein, the vanadium disulfide VS is hydrothermally obtained by taking ammonium metavanadate as a vanadium source and taking thioacetamide as a sulfur source 2 The material is coated on carbon paper to be used as a working electrode to participate in ENRR, and compared with severe competitive hydrogen evolution reaction in the process, the invention synthesizes VS 2 Soaking the material-coated carbon paper in alkyl mercaptan to obtain a surface alkyl mercaptan modified working electrode, and reducing the number of catalytic surface protons by introducing hydrophobic alkyl mercaptan to inhibit competitive hydrogen evolutionReaction to improve ENRR selectivity.

Description

Electrocatalytic material alkylthiol-VS for ENRR 2 Preparation method of (1)
Technical Field
The invention belongs to the field of ammonia production by electrocatalytic reduction of nitrogen, and particularly discloses an electrocatalytic material alkyl mercaptan-VS for ENRR 2 The preparation method of (1).
Background
Ammonia (NH) 3 ) As a commodity raw material, a fertilizer raw material and a chemical precursor, the organic hydrogen storage material is a substance necessary for maintaining human life and global economic development, and is also a novel effective hydrogen storage medium and a carbon-emission-free fuel. However, current industrial processes for ammonia production still rely heavily on the traditional energy intensive Haber-Bosch process (HBP). The Electrochemical Nitrogen Reduction Reaction (ENRR) has the advantages of coupling with green energy, no emission of CO2, use of abundant water instead of high-purity hydrogen, etc. due to its mild operating conditions at normal temperature and pressure, it is considered to be the most promising method to replace the Haber-Bosch process in recent years. Unfortunately, its practical application remains challenging, mainly due to the difficulty of cleavage of the strong dinitrogen bond, while a competitive hydrogen reduction reaction (HER) occurs, resulting in NH 3 The yield and efficiency are low. In view of the above problems, there is a strong need to develop a novel electrocatalyst having high ENRR catalytic performance.
Vanadium disulfide (VS) 2 ) Due to unique physicochemical properties and electronic configurations, the material is widely applied to the field of ENRR in recent years. However, at the conventional VS 2 In the electrocatalytic nitrogen reduction reaction, a large number of hydrogen evolution reaction sites are provided by rich sulfur edges, so that ENRR selectivity is poor, and FE is low. To solve this problem, surface alkylthiol-modified vanadium disulfide (alkylthiol-VS) was designed 2 ) As a catalytic material, the introduction of hydrophobic alkyl mercaptan can reduce the number of protons on a catalytic interface, thereby effectively inhibiting competitive HER reactions, and the catalytic selectivity of the catalyst in ENRR is excellent.
Disclosure of Invention
Aiming at the problem of poor selectivity of the existing catalyst, the invention aims to prepare a surface modification type catalyst alkyl mercaptan-VS capable of improving the selectivity of the catalyst 2 The method can improve the catalytic selectivity of ENRR in the reaction process, further improve FE and effectively inhibit competitive HER reaction.
To solve the above technical problems, the present invention provides an alkyl mercaptan modified vanadium disulfide (alkyl mercaptan-VS) for electrocatalytic reduction of nitrogen gas 2 ) Materials and methods for their preparation, including ammonium metavanadate and thioacetylMechanically stirring and mixing amine raw materials in ultrapure water, performing microwave hydrothermal treatment on the mixed solution, performing suction filtration, washing and vacuum drying on black solids obtained by hydrothermal treatment to obtain VS 2 A black powder material; taking a certain amount of VS 2 Dissolving the powder in ethanol-water-Nafion solution, performing ultrasonic treatment to obtain uniform oily solution, and uniformly coating a certain amount of the solution on carbon paper to obtain VS 2 A supported carbon paper material; finally, soaking the dried carbon paper in an alkyl mercaptan-ethanol solution saturated by argon to obtain the vanadium disulfide (alkyl mercaptan-VS) with the surface modified by alkyl mercaptan 2 ) An electrode material.
Further, the molar ratio of the ammonium metavanadate to the thioacetamide is 1:3.
further, the mechanical stirring and mixing is realized by magnetic stirring, and the specific stirring time is 1h.
Further, the specific process of the microwave hydrothermal method comprises the following steps: heating to 120 deg.C from room temperature for 10min, and maintaining the temperature for 8min; then heating to 150 ℃ for 10min, and preserving the heat for 8min at the temperature; then heating to 180 ℃ for 10min, and keeping the temperature for 120min; and finally, naturally cooling to room temperature.
Furthermore, the solvents used for suction filtration and washing are respectively absolute ethyl alcohol and ultrapure water, and the washing times are 3 times.
Further, the vacuum drying conditions are as follows: 30MPa, 60 ℃ and 24h.
Further, every 5mg VS 2 The powder corresponds to 800-1200 mul ethanol-water-Nafion solution; wherein the volume ratio of ethanol, water and Nafion solution is 654.
Further, the sonication time was 1h to obtain a homogeneous oily solution.
Further, every 1cm 2 The carbon paper size corresponds to 15-25. Mu.l of oily solution.
Further, the volume ratio of the alkyl mercaptan to the ethanol in the alkyl mercaptan-ethanol is 2.
Further, in the above-mentioned case,the soaking time is 5-20min, and the vanadium disulfide (alkyl mercaptan-VS) with the surface modified by alkyl mercaptan is taken out 2 )。
Further, the alkyl mercaptan is a C2-C12 alkyl mercaptan.
The invention effectively inhibits the competitive hydrogen evolution reaction while ensuring that the prepared material has certain catalytic activity, improves the reaction selectivity and ensures that the obtained material has uniform microstructure. The above features contribute to the intensive study of the ENRR process.
Drawings
FIG. 1 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 Schematic of the micro-topography of (a);
FIG. 2 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 Schematic comparison of water contact angle test of (1);
FIG. 3 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 Schematic diagram of the electrolysis apparatus of (1);
FIG. 4 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 A chronoamperometric schematic of (a);
FIG. 5 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 Ultraviolet-visible spectrum of (a);
FIG. 6 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 Comparative test ammonia yields of (a);
FIG. 7 is an alkyl mercaptan-VS electrocatalytic material for ENRR in accordance with the present invention 2 And VS 2 Comparative figure (c) shows the faraday efficiency of the test.
Detailed Description
The present invention will be described in more detail with reference to the following embodiments, but the present invention is not limited to the following examples.
An electrocatalytic material for ENRR, alkylmercaptan-VS, shown in FIG. 1 2 The material is mainly composed of VS 2 The catalyst coated carbon paper is loaded with alkyl mercaptan material.
Preparation methodThe method comprises the following steps: 5mmol of ammonium metavanadate, 15mmol of thioacetamide and 40mL of ultrapure water are mixed and stirred magnetically for 1h to obtain a black turbid solution. Transferring the solution into a microwave hydrothermal reaction kettle, wherein the hydrothermal synthesis process comprises the following steps: heating to 120 deg.C from room temperature for 10min, and maintaining the temperature for 8min; then heating to 150 ℃ for 10min, and preserving the heat for 8min at the temperature; then heating to 180 ℃ for 10min, and preserving the heat for 120min at the temperature; and finally naturally cooling to room temperature. Cooling to room temperature, vacuum filtering the obtained black solution, washing with anhydrous ethanol and ultrapure water for 3 times, and vacuum drying for 12 hr to obtain black solid powder VS 2 A material; 5mg of VS prepared by the above method 2 The powder was dissolved in 1000. Mu.l of a solution of ethanol-water-Nafion at a ratio of 654 2 The size is 2 × 1cm 2 To obtain carbon paper-supported VS 2 A material; and finally, soaking the dried carbon paper in 22ml of an alkyl mercaptan-ethanol solution with the ratio of argon saturated alkyl mercaptan to ethanol of 2 2 ) An electrode material.
In this embodiment, the electrode is characterized and analyzed in terms of its micro-morphology by using a scanning electron microscope, and it can be seen from fig. 1 that the material is mainly composed of VS 2 The catalyst coated carbon paper is loaded with alkyl mercaptan material.
FIG. 2 is a comparative illustration of water contact angle testing of materials of the present invention. As can be seen from the figure, the material of the invention has a water contact angle of more than 90 degrees and belongs to a hydrophobic material; and VS 2 The contact angle of the water is less than 90 degrees, and the water belongs to hydrophilic materials. The results of the above tests demonstrate that the alkanethiol-VS 2 The successful synthesis of the material and the material of the invention have better hydrophobicity, thereby effectively inhibiting competitive hydrogen evolution reaction.
FIG. 3 is a schematic view of an electrolysis apparatus for the material of the present invention; the working electrode is the alkyl mercaptan-VS 2 of the electrocatalytic material of the invention, the counter electrode is a silver/silver chloride reference electrode, and double electrodes are adoptedA decomposition chamber, wherein the specific parameters are as follows: after the 0.1M Na2SO4 electrolyte is purified for 30min by N2, an N2 reduction experiment is carried out. In N 2 Saturated 0.1M Na 2 SO 4 In solution is subjected to N 2 And (4) performing electrochemical reduction. After electrolysis for a period of time at a controlled potential (-0.10 to-0.30V vs. RHE), the electrolyte in the cathode cell was collected for color development, and its absorbance was measured by UV spectrophotometry to calculate its ammonia yield and Faraday Efficiency (FE). The calculation formula is as follows:
NH 3 the generation rate calculation formula of (1) is as follows:
Figure BDA0003733729800000051
Figure BDA0003733729800000052
for ammonia production, the unit is
Figure BDA0003733729800000053
Figure BDA0003733729800000054
For NH in the electrolyte 3 In units of μ g mL -1 (ii) a V is the volume of the electrolyte, and the unit is mL; t is electrolysis time, and the unit is h; m is cat Is the mass of the electrode material in mg.
The FE calculation formula is as follows:
Figure BDA0003733729800000055
FE is Faraday efficiency, unit is%; f is the Faraday constant and has a value of 96500C mol -1 (ii) a Q is the total charge consumption of the electrolysis process and is given in C.
Fig. 4 is an ampere-hour diagram of the material of the present invention. The specific parameters are as follows: potential settings are-0.10, -0.15, -0.20, -0.25, -0.30V vs. RHE, respectively; the dot interval is 0.05s; the running time is 7200s; the sensitivity was 0.1A/V. As can be seen from fig. 5, the corresponding current fluctuates within a small range at different potentials, demonstrating a certain catalytic stability of the material.
FIG. 5 is a schematic diagram of the UV-VIS spectrum of the material of the present invention. As can be seen from the figure, the material of the present invention has higher NH at 655nm wavelength under the optimal reduction potential 3 Absorption peaks prove that the material has more excellent electro-catalysis ammonia generation performance.
FIG. 6 is a schematic diagram of the ammonia production of the material of the present invention. As can be seen from the figure, the ammonia production of the material of the invention is all higher than VS at the same reduction potential 2 And the highest value reaches 58.1 mu g h -1 mg cat -1 And VS is 2 The highest ammonia yield of the ammonia is only 20.6 mu g h -1 mg cat -1 . The material of the invention is proved to have more excellent electro-catalysis ammonia production performance.
Figure 7 is a schematic representation of the faradaic efficiency of the material of the present invention. It can be seen from the figure that the FE values of the materials of the invention are all higher than VS at the same reduction potential 2 And up to 34.5%, and VS 2 The highest FE value of (a) is only 8.7%. The material of the invention is proved to have higher selectivity.
The foregoing is merely an example of the present invention and common general knowledge of known specific structures and features of the embodiments is not described herein in any greater detail. It should be noted that, for those skilled in the art, without departing from the structure of the present invention, several changes and modifications can be made, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicability of the patent.

Claims (10)

1. Alkyl mercaptan-VS for electro-catalytic reduction of nitrogen 2 The preparation method of the material is characterized by comprising the steps of mechanically stirring and mixing ammonium metavanadate and thioacetamide raw materials in ultrapure water, carrying out microwave hydrothermal treatment on the mixed solution, carrying out suction filtration, washing and vacuum drying on black solids obtained by the hydrothermal treatment to obtain VS 2 A black powder material; take a certain amount of VS 2 Dissolving the powder in ethanol-water-Nafion solution, and performing ultrasonic treatment to obtain uniform oily solutionUniformly coating a certain amount of the solution on carbon paper to obtain VS 2 A supported carbon paper material; finally, soaking the dried carbon paper in an alkyl mercaptan-ethanol solution saturated by argon to obtain a vanadium disulfide electrode material modified by alkyl mercaptan on the surface, namely alkyl mercaptan-VS 2 A material.
2. The method according to claim 1, wherein the molar ratio of ammonium metavanadate to thioacetamide is 1:3; the specific process of the microwave hydrothermal method comprises the following steps: heating to 120 deg.C from room temperature for 10min, and maintaining the temperature for 8min; then heating to 150 ℃ for 10min, and preserving the heat for 8min at the temperature; then heating to 180 ℃ for 10min, and keeping the temperature for 120min; and finally, naturally cooling to room temperature.
3. The method according to claim 1, wherein the solvents used for suction filtration washing are absolute ethyl alcohol and ultrapure water respectively, and the washing times are 3 times; the specific conditions of the vacuum drying are as follows: 30MPa, 60 ℃ and 24h.
4. The method of claim 1 wherein each 5mg VS 2 The powder corresponds to 800-1200 mul ethanol-water-Nafion solution; wherein the volume ratio of ethanol, water and Nafion solution is 654.
5. A method according to claim 1, characterized in that every 1cm 2 The carbon paper size corresponds to 15-25. Mu.l of oily solution.
6. The process according to claim 1, wherein the alkyl mercaptan-ethanol has a volume ratio of alkyl mercaptan to ethanol of 2.
7. The method according to claim 1, wherein the soaking time is 5-20min, and the vanadium disulfide modified by alkyl mercaptan of C2-C12 is obtained by taking out.
8. alkanethiol-VS prepared by the process according to any of claims 1 to 7 2 A material.
9. alkanethiol-VS prepared by the process according to any of claims 1 to 7 2 The material is applied as an electrode for preparing ammonia by electrocatalytic reduction of nitrogen.
10. The method according to claim 9, characterized in that the working electrode is an alkyl mercaptan-VS 2 electrocatalytic material and the counter electrode is a silver/silver chloride reference electrode, a double cell is used, the specific parameters being: 0.1M of Na 2 SO 4 Electrolyte solution of N 2 After 30min of purification, N is carried out 2 Reduction experiment; in N 2 Saturated 0.1M Na 2 SO 4 In solution is subjected to N 2 Electrochemical reduction; RHE at control potentials of-0.10 to-0.30V vs.
CN202210807086.3A 2022-07-06 2022-07-06 Electrocatalytic material alkylthiol-VS for ENRR 2 Preparation method of (1) Pending CN115161667A (en)

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