A tungsten disulfide / tungsten trioxide nanoflower electrode and its preparation method and application

Abstract

The present invention discloses a tungsten disulfide / tungsten trioxide nanoflower electrode and a preparation method and application thereof, the method comprising: adding a sulfur source to an aqueous solution containing a tungsten source, mixing evenly, and obtaining a mixed solution; dripping an auxiliary agent into the mixed solution, stirring during the dripping process, and aerating the obtained solution in oxygen after the dripping to obtain a precursor solution; pouring into a reactor, immersing the pretreated carbon cloth in the solution in the reactor, performing a hydrothermal reaction, and washing the electrode after the reaction, and drying to obtain a tungsten disulfide / tungsten trioxide nanoflower electrode. The present invention solves the difficult problem of coupling hydrogen evolution reaction and carbon dioxide microbial electrosynthesis. The control of the hydrogen evolution rate of the material is achieved by controlling the synthesis temperature, so that the rate of in-situ electrochemical hydrogen production of the electrode and the rate of hydrogen consumption by the microorganisms are balanced, and a high coulomb efficiency of the product acetic acid is obtained.

Description

Technical Field

[0001] The present invention relates to the field of composite material electrodes for bioelectrochemical systems, and in particular to a tungsten disulfide / tungsten trioxide nanoflower electrode, a preparation method of the electrode, and application of the electrode as a cathode in bioelectrochemical reduction of carbon dioxide. Background Art

[0002] CO2 bioutilization technology is a technology that converts CO2 into useful products such as food, feed, biofertilizer and biofuel through a biological conversion process. It is considered to be a cost-effective way to achieve a circular carbon economy. In recent years, microbial electrosynthesis (MES), which cleverly combines electroreduction with microbial conversion, has attracted much attention. MES relies on functional microorganisms to directly or indirectly absorb electrons from the cathode as reducing equivalents, and then converts CO2 into target high-value chemicals such as formic acid, acetic acid and ethanol under relatively mild conditions. In CO2 bioelectrochemical conversion, the main electron transfer pathway is indirect electron transfer. Compared with other electron mediators, hydrogen, as the main electron mediator, can be produced under neutral conditions as long as the voltage reaches -0.41 V vs. SHE. Therefore, many studies combine hydrogen evolution catalysts with MES to achieve the reduction of CO2.

[0003] Considering the need to couple the hydrogen evolution reaction with microorganisms, the selected hydrogen evolution catalyst should have good biocompatibility. Tungsten disulfide and tungsten trioxide are common hydrogen evolution catalysts. Tungsten disulfide is considered to be the preferred material for replacing precious metals such as Pt / Ir as the next generation of hydrogen evolution catalysts due to its adjustable band gap, near-zero hydrogen evolution Gibbs free energy and high cost-effectiveness. Tungsten disulfide can provide abundant active sites and good conductivity, while tungsten trioxide can increase the redox ability of the catalyst. In addition, both have good biocompatibility. After the introduction of the hydrogen evolution catalyst into the MES, although the concentration of the target product increased, the coulombic efficiency (CE) of the product was between 20% and 60%. This is because most of the electrons are used to produce hydrogen, and the produced hydrogen cannot be consumed in time, resulting in too low CE of the target product. Some studies have proposed to control the potential of the cathode to control the hydrogen evolution rate in order to improve the coulombic efficiency of the product, but few people have controlled the hydrogen evolution rate by controlling the hydrogen evolution performance of the hydrogen evolution catalyst. Taking this into consideration, the present invention controls the hydrogen evolution activity of the tungsten disulfide / tungsten trioxide nanoflower electrode by controlling the synthesis temperature, so that the hydrogen generated in situ by the electrode can be used by microorganisms in a timely manner, achieving a balance between hydrogen production and consumption, and further achieving high yield and high coulomb efficiency of acetic acid. Summary of the invention

[0004] In order to overcome the shortcomings and deficiencies of the prior art, the present invention provides a tungsten disulfide / tungsten trioxide nanoflower electrode and a preparation method and application thereof. The tungsten disulfide / tungsten trioxide nanoflower electrode is used as a cathode for microbial electrosynthesis and reduction of carbon dioxide. The composite electrode has good hydrogen evolution activity and biocompatibility.

[0005] The present invention solves the difficult problem of coupling the hydrogen evolution reaction and the carbon dioxide microbial electrosynthesis, that is, the problem that the hydrogen at the cathode cannot be consumed by the microorganisms, resulting in low coulombic efficiency of the target product.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a tungsten disulfide / tungsten trioxide nanoflower electrode comprises the following steps:

[0008] Step S1, adding a sulfur source to an aqueous solution containing a tungsten source, mixing them evenly to obtain a mixed solution;

[0009] Step S2, adding an auxiliary agent dropwise to the mixed solution, stirring during the dropping process, and aerating the resulting solution in oxygen for 4 to 6 hours after the dropping to obtain a precursor solution;

[0010] Step S3, adjusting the pH of the precursor solution to maintain at 5.6-7.4, then pouring it into a reactor, immersing the pretreated carbon cloth in the solution in the reactor, performing a hydrothermal reaction at 140-200° C., and obtaining a reacted electrode after the reaction is completed;

[0011] Step S4: After cleaning the electrode after the reaction, dry it at 60-80° C. in a nitrogen or inert gas atmosphere for 12-16 h to obtain a tungsten disulfide / tungsten trioxide nanoflower electrode.

[0012] The electrode of the present invention is to grow tungsten disulfide / tungsten trioxide nanoflowers on pretreated carbon cloth fibers by a hydrothermal method, and control the hydrogen evolution rate by setting the temperature (200°C, 170°C and 140°C).

[0013] The present invention uses a hydrothermal method to grow tungsten disulfide / tungsten trioxide nanoflowers on a carbon cloth substrate to obtain tungsten disulfide / tungsten trioxide nanoflower electrodes with different sizes. The rate of hydrogen evolution of the material is controlled by controlling the synthesis temperature, so that the rate of in-situ electrochemical hydrogen production of the electrode and the rate of hydrogen consumption by the microorganisms are balanced, and the high coulomb efficiency of the product acetic acid is obtained. This not only improves the electron transfer rate and electron utilization efficiency between the microorganisms and the electrode, but also promotes the application of microbial electrosynthesis systems in circular bioeconomy and the production of high-value biofuels using carbon dioxide.

[0014] Further, the carbon cloth pretreatment method:

[0015] First, immerse the carbon cloth in a mixed solution of nitric acid and deionized water in a volume ratio of 1:1, ultrasonicate for 15 to 20 minutes, and then wash the carbon cloth with deionized water several times; immerse it in an ethanol solution, ultrasonicate again for 15 to 20 minutes, and wash it with deionized water several times to complete the pretreatment.

[0016] Furthermore, the tungsten disulfide / tungsten trioxide nanoflower electrode is prepared as follows:

[0017] The tungsten source and the sulfur source are added to 60 mL of deionized water at a mass ratio of 0.70-0.80:1, preferably 0.75:1; constant temperature magnetic stirring for 20-30 min, preferably 30 min; add the auxiliary agent to the above solution (the mass ratio of the auxiliary agent to the tungsten source is maintained at 0.5-0.6:1, preferably 0.55:1), magnetic stirring for 5-10 min, preferably 10 min; aerate the obtained solution (O2) for 4-6 h, preferably 5 h, and pour it into a polytetrafluoroethylene reactor, and perform hydrothermal reaction at 200°C, 170°C and 140°C, respectively, for 24 h; after the reaction, wash the obtained electrode with ethanol for 3 times or more and then with deionized water for 3 times or more, and dry it under nitrogen atmosphere to obtain tungsten disulfide / tungsten trioxide nanoflower electrodes with different nanoflower sizes, and the preparation is completed. The sulfur source is thioacetamide or thiourea; the tungsten source is sodium tungstate.

[0018] The application of the tungsten disulfide / tungsten trioxide nanoflower electrode in the hydrogen evolution reaction specifically includes: in a three-electrode electrolytic cell with a cathode, an anode and a reference electrode, the tungsten disulfide / tungsten trioxide nanoflower electrode is used as the cathode, the graphite sheet is used as the anode, the electrolyte is a phosphate buffer solution, and power is applied to carry out the hydrogen evolution reaction.

[0019] The application of the tungsten disulfide / tungsten trioxide nanoflower electrode as a bioelectrochemical electrode specifically includes: in an H-type reactor, the tungsten disulfide / tungsten trioxide nanoflower electrode is used as a cathode, an inorganic salt solution is used as a cathode electrolyte, a graphite sheet is used as an anode, and a phosphate buffer solution is used as an anode electrolyte to perform a bioelectrochemical reduction reaction to convert carbon dioxide into acetic acid. After adding activated sludge to the cathode electrolyte, 2 g / L sodium bicarbonate (NaHCO3) is added as an inorganic carbon source and 1 g / L sodium 2-bromoethane sulfonate (BrCH2CH2SO3Na) is added as a methane inhibitor. Through an electrochemical workstation, the cathode potential is controlled to be -0.85 V vs. SHE, the concentration of acetic acid in the cathode liquid is monitored, and when the concentration of acetic acid in the cathode electrolyte begins to decrease, the cathode electrolyte is replaced and the inorganic carbon source and methane inhibitor are added to the cathode electrolyte again.

[0020] The inorganic salt solution consists of a phosphate buffer solution, a trace element solution and a vitamin solution.

[0021] The composition of the phosphate buffer solution is: NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO4 4.576 g / L, KCl 0.13 g / L, and the solvent is deionized water;

[0022] The trace element solution comprises: MgSO4 3 g / L, MnSO4·H2O 0.5 g / L, NaCl 1 g / L, FeSO4·7H2O 0.1 g / L, CaCl2·2H2O 0.1 g / L, CoCl2·6H2O 0.1 g / L, ZnCl2 0.13 g / L, CuSO4·5H2O 0.01 g / L, AlK(SO4)2·12H2O 0.01 g / L, H3BO3 0.01 g / L, Na2MoO4 0.025 g / L, and Na2WO4·2H2O 0.025 g / L, and the solvent is deionized water;

[0023] The vitamin solution is composed of: 0.002 g / L biotin, 0.002 g / L folic acid, 0.01 g / L pyridoxine, 0.005 g / L riboflavin, 0.005 g / L thiamine, 0.005 g / L niacin, 0.005 g / L pantothenic acid, 0.0001 g / L B-12, 0.005 g / L p-aminobenzoic acid, and 0.005 g / L lipoic acid, and the solvent is deionized water.

[0024] Furthermore, the application is as follows: an H-type reactor and an electrochemical workstation are used to form a bioelectrochemical system; the cathode chamber and the anode chamber of the H-type reactor are separated by a proton exchange membrane; a tungsten disulfide / tungsten trioxide nanoflower electrode is a working electrode, a graphite sheet is a counter electrode, and a reference electrode is Ag / AgCl (+0.197 V vs. SHE); the cells are connected via an electrochemical workstation and cultured under optimal environmental factor conditions (culture temperature 30°C, culture solution pH=7); when the acetic acid production of each batch begins to decrease, the cathode and anode liquids are replaced, the anode is replaced with a fresh phosphate buffer solution, and the cathode is replaced with an inorganic salt solution, an inorganic carbon source, and a methane inhibitor.

[0025] Compared with the prior art, the beneficial effects of the present invention are mainly reflected in:

[0026] (1) Compared with traditional materials, the synthesized nanoflower structure of the tungsten disulfide / tungsten trioxide nanoflower electrode of the present invention has a higher specific surface area and more surface active sites, so it has better catalytic, adsorption, sensing and other properties. In addition, the preparation method requires simple equipment, convenient operation, easy control of conditions, and low energy consumption.

[0027] (2) The tungsten disulfide / tungsten trioxide nanoflower electrode of the present invention can control its hydrogen evolution rate by controlling the temperature. It not only has good conductivity, but also realizes efficient transfer and full utilization of electrons in CO2 bioelectrochemical reduction.

[0028] (3) The three-dimensional structure of tungsten disulfide / tungsten trioxide nanoflower electrode is beneficial to the attachment and growth of electroactive microorganisms, the formation of biofilm and the conduction of electrons. Compared with the traditional carbon neutralization method, the application of tungsten disulfide / tungsten trioxide nanoflower electrode in bioelectrochemical system does not produce any secondary pollution in the process of reducing CO2, is easy to promote and has low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The SEM scanning electron microscope images of tungsten disulfide / tungsten trioxide nanoflower electrodes synthesized at different temperatures prepared in Examples 1 to 3, wherein: Figure 1 A and Figure 1 Figure d is a SEM image of the tungsten sulfide / tungsten trioxide nanoflower electrode synthesized at 200°C in Example 1. Figure 1 Medium b and Figure 1 Figure e is a SEM image of the tungsten sulfide / tungsten trioxide nanoflower electrode synthesized at 170°C in Example 2. Figure 1 Medium c and Figure 1 Figure f is a SEM scanning electron microscope image of the tungsten sulfide / tungsten trioxide nanoflower electrode synthesized at 140°C in Example 3.

[0030] Figure 2 The X-ray photoelectron spectra of the tungsten disulfide / tungsten trioxide nanoflower electrodes prepared at different temperatures in Examples 1 to 3 are as follows ( Figure 2 a) and W 4f, S 2p and O 1s ( Figure 2 b~d) spectra, wherein WS2 / WO3-10 is WS2 / WO3-200 prepared in Example 1, WS2 / WO3-7 is WS2 / WO3-170 prepared in Example 2, and WS2 / WO3-4 is WS2 / WO3-140 prepared in Example 3.

[0031] Figure 3 LSV diagram of polarization curves of tungsten disulfide / tungsten trioxide nanoflower electrodes synthesized at different temperatures in Application Example 1, wherein WS2 / WO3-10 is WS2 / WO3-200 prepared in Example 1, WS2 / WO3-7 is WS2 / WO3-170 prepared in Example 2, WS2 / WO3-4 is WS2 / WO3-140 prepared in Example 3, and CC is the product prepared in the control example.

[0032] Figure 4The yield of acetic acid from the reduction of CO2 using the tungsten disulfide / tungsten trioxide nanoflower electrode as the cathode in Application Example 2 ( Figure 4 a) and the corresponding Coulombic efficiency (CE) ( Figure 4 b), wherein WS2 / WO3-10 is WS2 / WO3-200 prepared in Example 1, WS2 / WO3-7 is WS2 / WO3-170 prepared in Example 2, WS2 / WO3-4 is WS2 / WO3-140 prepared in Example 3, and CC is the product prepared in the control example. DETAILED DESCRIPTION

[0033] The present invention is further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0034] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources. The room temperature in the present invention refers to 25°C.

[0035] Comparison example:

[0036] The control example is a carbon cloth without modification of tungsten disulfide / tungsten trioxide as the cathode electrode. The carbon cloth was pretreated as follows: the carbon cloth (Suzhou Shengernuo Technology Co., Ltd., WOS1011) was immersed in a mixed solution of nitric acid and deionized water with a volume ratio of 1:1, ultrasonicated for 15-20 min, and then washed with deionized water several times; the carbon cloth was immersed in an ethanol solution, ultrasonicated again for 15-20 min, and washed with deionized water several times to complete the pretreatment. Using an electrochemical workstation (VSP, Bio-Logic, France) and an H-type reactor (Tianjin Gaoshi Ruilian Technology Co., Ltd., C007-1), under the optimal environmental factor conditions (culture temperature 30℃, culture medium pH=7), 10 mL of activated sludge (Qige Wastewater Treatment Plant, Hangzhou) and 70 mL of inorganic salt solution (phosphate buffer solution + trace elements + vitamin solution) were added to the cathode chamber, and 80 mL of 50 mM phosphate buffer solution was added to the anode chamber. High-purity nitrogen was introduced to drive out the oxygen in the cathode and anode chambers. In addition, 2 g / L sodium bicarbonate as an inorganic carbon source and 1 g / L sodium 2-bromoethane sulfonate (methane inhibitor) were directly added to the cathode chamber. The cathode potential was controlled at -0.85 V vs. SHE using the electrochemical workstation.

[0037] Example 1: Preparation of tungsten disulfide / tungsten trioxide nanoflower electrodes at 200°C

[0038] Sodium tungstate dihydrate (Na2WO4·2H2O) was added to 60 mL of deionized water. After magnetic stirring, thioacetamide (C2H5NS) was added dropwise to the mixture. The mixture was magnetically stirred for 30 min to obtain a clear and transparent solution. The mass ratio of the added tungsten source to the sulfur source was 0.75:1. Oxalic acid dihydrate (H2C2O4·2H2O) was added to the clear and transparent solution. The mass ratio of the added oxalic acid to the sulfur source was 0.0032:1. After magnetic stirring for 10 min, the obtained solution was aerated (O2) for 5 h. Hydrochloric acid and sodium hydroxide solution were added dropwise to maintain the pH of the mixed solution at 6.5. The mixed solution was poured into a polytetrafluoroethylene reactor and the pretreated carbon cloth (2×3 cm) (same as the control example) was immersed in the solution. The hydrothermal reaction was carried out at 200°C for 24 h. h; After the reaction is completed, the obtained electrode is washed with ethanol and deionized water several times, and dried at 70 ° C in a nitrogen atmosphere for 14 h to obtain a tungsten sulfide / tungsten trioxide nanoflower electrode synthesized at 200 ° C, named WS2 / WO3-200.

[0039] Example 2: Preparation of tungsten disulfide / tungsten trioxide nanoflower electrodes at 170°C

[0040] Sodium tungstate dihydrate (Na2WO4·2H2O) was added to 60 mL of deionized water. After magnetic stirring, thioacetamide (C2H5NS) was added dropwise to the mixture. The mixture was magnetically stirred for 30 min to obtain a clear and transparent solution. The mass ratio of the added tungsten source to the sulfur source was 0.75:1. Oxalic acid dihydrate (H2C2O4·2H2O) was added to the clear and transparent solution. The mass ratio of the added oxalic acid to the sulfur source was 0.0032:1. After magnetic stirring for 10 min, the obtained solution was aerated (O2) for 5 h. Hydrochloric acid and sodium hydroxide solution were added dropwise to maintain the pH of the mixed solution at 6.5. The mixed solution was poured into a polytetrafluoroethylene reactor and the pretreated carbon cloth (2×3 cm) (same as the control example) was immersed in the solution. The hydrothermal reaction was carried out at 170°C for 24 h. h; After the reaction is completed, the obtained electrode is washed with ethanol and deionized water several times, and dried in a nitrogen atmosphere at 70 ° C for 14 h to obtain a tungsten sulfide / tungsten trioxide nanoflower electrode synthesized at 170 ° C. The obtained electrode is named WS2 / WO3-170.

[0041] Example 3: Preparation of tungsten disulfide / tungsten trioxide nanoflower electrodes at 140°C

[0042] Sodium tungstate dihydrate (Na2WO4·2H2O) was added to 60 mL of deionized water. After magnetic stirring, thioacetamide (C2H5NS) was added dropwise to the mixture. The mixture was magnetically stirred for 30 min to obtain a clear and transparent solution. The mass ratio of the added tungsten source to the sulfur source was 0.75. Oxalic acid dihydrate (H2C2O4·2H2O) was added to the clear and transparent solution. The mass ratio of the added oxalic acid to the sulfur source was 0.0032. After magnetic stirring for 10 min, the obtained solution was aerated (O2) for 5 h. Hydrochloric acid and sodium hydroxide solution were added dropwise to maintain the pH of the mixed solution at 6.5. The mixed solution was poured into a polytetrafluoroethylene reactor and the pretreated carbon cloth (2×3 cm) (same as the control example) was immersed in the solution. The hydrothermal reaction was carried out at 140°C for 24 h. After the reaction, the obtained electrode was washed with ethanol and deionized water several times and dried at 70°C in a nitrogen atmosphere for 14 After h, the tungsten sulfide / tungsten trioxide nanoflower electrode synthesized at 140°C can be obtained, and the obtained electrode is named WS2 / WO3-140.

[0043] Depend on Figure 1 It can be seen that as the temperature increases, the size of the synthesized nanoflowers and nanosheets increases. Figure 2 It can be found that the two low binding energy peaks at 32.8 eV and 34.9 eV correspond to the low-valent W 4+ W 4f 7 / 2 and W 4f 5 / 2 , while the two peaks at high binding energies of 35.6 eV and 37.7 eV correspond to the high-valent W 6+ The contents of tetravalent tungsten and hexavalent tungsten in different electrodes are different. 4+ and W 6+ The peak area integration found W 4+ / W 6+ The ratios decrease with temperature, becoming 4.1, 3.6 and 1.44, respectively. From the O1s spectrum, it can be seen that all samples show three O1s peaks at 533.2 eV, 530 eV and 531.6 eV, corresponding to physically adsorbed water, O atoms near surface oxygen vacancies and lattice oxygen in metal oxides (from WO3). In addition, the O content increases with decreasing temperature.

[0044] Application Example 1: Hydrogen evolution performance test of tungsten disulfide / tungsten trioxide nanoflower electrodes synthesized at different temperatures

[0045] In a three-electrode electrolytic cell with a cathode, an anode and a reference electrode, a tungsten disulfide / tungsten trioxide nanoflower electrode is used as the cathode, a graphite sheet is used as the anode, and the electrolyte is a phosphate buffer solution, and the hydrogen evolution reaction is carried out by powering on. The tungsten disulfide / tungsten trioxide nanoflower electrode is subjected to a three-electrode electrochemical test in a 50 mM phosphate buffer solution to explore the hydrogen evolution reaction performance of the three tungsten disulfide / tungsten trioxide nanoflower electrodes prepared in Examples 1 to 3. Connected through an electrochemical workstation (same as the control example), the tungsten disulfide / tungsten trioxide nanoflower electrode prepared in Example 1 is the working electrode, the graphite sheet (2×3×0.3 cm) is the counter electrode, and the reference electrode is Ag / AgCl (+0.197 V vs. SHE). Figure 3 The polarization curve LSV diagram of the tungsten disulfide / tungsten trioxide nanoflower electrode synthesized at different temperatures in Application Example 1 shows that the higher the temperature, the better the hydrogen evolution performance of the synthesized electrode. Specifically, WS2 / WO3-200 has the best hydrogen evolution performance, followed by WS2 / WO3-170 and WS2 / WO3-140.

[0046] Application Example 2: Cathode Acetic Acid Production of Tungsten Disulfide / Tungsten Trioxide Nanoflowers

[0047] Using an electrochemical workstation (same as the control example) and an H-type reactor (Tianjin Gaoshi Ruilian Technology Co., Ltd., C007-1), under the optimal environmental factor conditions (culture temperature 30°C, culture solution pH=7), 10 mL of activated sludge (Qige Sewage Treatment Plant, Hangzhou) and 70 mL of inorganic salt solution (phosphate buffer solution + trace elements + vitamin solution) were added to the cathode chamber, 80 mL of 50 mM phosphate buffer solution was added to the anode chamber, high-purity nitrogen was introduced to drive out oxygen in the cathode and anode chambers, and 2 g / L of sodium bicarbonate was directly added to the cathode chamber as a carbon source, and the cathode potential was controlled by the electrochemical workstation to -0.85 Vvs. SHE. The cathode electrodes were tungsten disulfide / tungsten trioxide nanoflowers (working electrode) and graphite sheets (counter electrode) prepared in Example 1. The concentration of acetic acid in the cathode liquid was detected by gas chromatography. When the concentration of acetic acid in each batch began to decrease, the anode and cathode liquids were replaced, the cathode was replaced with 80 mL of fresh inorganic salt solution and 2 g / L sodium bicarbonate solution, and the anode was replaced with 80 mL of phosphate buffer solution. The results are shown in the figure. Figure 4 As shown, the concentration of acetic acid produced by WS2 / WO3-4 is the highest, reaching 872.32 mg / L, which is 3.4 times that of the control example, and the coulombic efficiency of acetic acid of the electrode can reach 77.73%, which is much higher than that of WS2 / WO3-7 and WS2 / WO3-10. It can be seen that the hydrogen evolution rate of the WS2 / WO3-4 electrode prepared in Example 1 and the rate of hydrogen consumption by microorganisms tend to be balanced, and most of the hydrogen produced is used by organisms.

[0048] Gas chromatography detection conditions: 6890N GC (Agilent, USA), using an HP Innowax capillary column (30 m×320 μm×0.5 μm). The carrier gas N2 was supplied at a flow rate of 40 mL / min, and the air flow rate was 450 mL / min. The temperatures of the injection port and detector were set to 250°C and 200°C, respectively.

[0049] Each 1 L of inorganic salt solution is mixed with 982.5 mL of phosphate buffer solution, 12.5 mL of trace element solution, and 5 mL of vitamin solution.

[0050] The composition of phosphate buffer solution is: NH4Cl 0.31 g / L, NaH2PO4·H2O 2.452 g / L, Na2HPO44.576 g / L, KCl 0.13 g / L, and the solvent is deionized water;

[0051] The composition of the trace element solution is: MgSO4 3 g / L, MnSO4·H2O 0.5 g / L, NaCl 1 g / L, FeSO4·7H2O 0.1 g / L, CaCl2·2H2O 0.1 g / L, CoCl2·6H2O 0.1 g / L, ZnCl2 0.13 g / L, CuSO4·5H2O0.01 g / L, AlK(SO4)2·12H2O 0.01 g / L, H3BO3 0.01 g / L, Na2MoO4 0.025 g / L, Na2WO4·2H2O0.025 g / L, and the solvent is deionized water;

[0052] The composition of the vitamin solution is: biotin 0.002 g / L, folic acid 0.002 g / L, pyridoxine 0.01 g / L, riboflavin 0.005 g / L, thiamine 0.005 g / L, niacin 0.005 g / L, pantothenic acid 0.005 g / L, B-12 0.0001 g / L, p-aminobenzoic acid 0.005 g / L, and lipoic acid 0.005 g / L, and the solvent is deionized water.

[0053] Although the present invention has been disclosed as above by way of embodiments, it is not intended to limit the protection scope of the present invention. Any changes and modifications made by any technician familiar with the technology without departing from the concept and scope of the present invention should fall within the protection scope of the present invention.

Claims

1. A method for preparing a tungsten disulfide / tungsten trioxide nanoflower electrode, characterized in that: The following steps are involved: Step S1, adding a sulfur source to an aqueous solution containing a tungsten source, mixing them evenly to obtain a mixed solution; The sulfur source is thioacetamide or thiourea; The tungsten source is sodium tungstate; The mass ratio of the tungsten source to the sulfur source is 0.70-0.80:1; Step S2, adding an auxiliary agent dropwise to the mixed solution, stirring during the dropping process, and aerating the resulting solution in oxygen for 4 to 6 hours after the dropping to obtain a precursor solution; The auxiliary agent is sodium diethyldithiocarbamate or oxalic acid; Step S3, adjusting the pH of the precursor solution to maintain at 5.6-7.4, then pouring it into a reactor, immersing the pretreated carbon cloth in the solution in the reactor, and performing a hydrothermal reaction at 140-200° C. The hydrothermal reaction time is 20-40 hours, and after the reaction is completed, a reacted electrode is obtained; Step S4: After the reacted electrode is cleaned, it is dried to obtain a tungsten disulfide / tungsten trioxide nanoflower electrode.

2. The method for preparing the tungsten disulfide / tungsten trioxide nanoflower electrode according to claim 1, characterized in that: In step S4, drying is performed under a nitrogen or inert gas atmosphere.

3. The method for preparing the tungsten disulfide / tungsten trioxide nanoflower electrode according to claim 2, characterized in that: In step S4, drying is performed at 60-80° C. in a nitrogen or inert gas atmosphere for 12-16 hours.

4. A tungsten disulfide / tungsten trioxide nanoflower electrode prepared according to the preparation method according to any one of claims 1 to 3.

5. The use of the tungsten disulfide / tungsten trioxide nanoflower electrode in hydrogen evolution reaction according to claim 4, characterized in that: Specifically include: In a three-electrode electrolytic cell with a cathode, an anode and a reference electrode, a tungsten disulfide / tungsten trioxide nanoflower electrode is used as the cathode, a graphite sheet is used as the anode, and the electrolyte is a phosphate buffer solution. Electricity is applied to carry out hydrogen evolution reaction.

6. The use of the tungsten disulfide / tungsten trioxide nanoflower electrode as a bioelectrochemical electrode according to claim 4, characterized in that: Specifically include: In an H-type reactor, a tungsten disulfide / tungsten trioxide nanoflower electrode is used as the cathode, an inorganic salt solution is used as the cathode electrolyte, a graphite sheet is used as the anode, and a phosphate buffer solution is used as the anode electrolyte to carry out a bioelectrochemical reduction reaction to convert carbon dioxide into acetic acid.

Images