Preparation Of MoS₂/AOCF Catalyst And Study On The Performance Of Electrocatalytic Hydrogen Evolution

In the 21st century,energy and environment are the key issues related to national and social development.The environmental pollution caused by the backward energy extraction technology in the early stage has made the global ecology worsen day by day.Therefore,the preparation of clean energy such as hydrogen is particularly important.Among them,electrocatalytic hydrogen production is attracting more and more attention due to its advantages of non-toxicity,harmlessness and pollution-free.In this study,amidoxime-modified polyacrylonitrile fibers were dissolved in dimethyl sulfoxide solvent to obtain a uniform and stable amidoxime-modified polyacrylonitrile polymer solution.As a solvent for the synthesis of MoS2 catalytic materials,-OH and-NH2 groups on the polymer chain of amidoxime groups can form coordination bonds with Mo atoms in MoS2,so that the eventually synthesized MoS2 catalytic materials can be tightly combined with amidoxime substratum through coordination.The performance of the composite catalyst is stable and not easy to fall off after it is coated on the surface of glassy carbon electrode.The presence of amidoxime polymer film substrate enables the MoS2 material that is prone to agglomeration to grow on the surface of the substrate,thus greatly increasing the specific surface area of the catalyst.This can expose more active sites in MoS2 and improve the electrocatalytic hydrogen evolution ability of the catalyst.In this study,the electrocatalytic performance of electrode materials prepared by dropping the catalyst on the glassy carbon electrode was taken as the index,and the optimum process condition for preparing MoS2/AOCF was explored by investigating the ratio of the synthetic materials,the time and temperature of solvent thermal reaction and other conditions.The catalyst was characterized and analyzed by SEM,TEM,XRD and XPS.The electrocatalytic performance of the catalyst was studied by analyzing its steady-state polarization curve,tafel slope,cyclic stability test,double-layer capacitance,electrochemical impedance,etc.The results are shown below:(1)Investigation on the preparation conditions of MoS2/AOCF catalytic materials.The optimal preparation conditions of MoS2/AOCF catalytic materials were as follows:the dosage of thioacetamide was 10.0 mmol,and the dosage of sodium molybdate dihydrate was 1.0 mmol.The reaction temperature is 130 ?.The reaction time was 12 h.The agglomeration of MoS2 and amidoxime fiber substratum was obviously improved after the combination of MoS2 and amidoxime substratum.Compared with the bulk MoS2 which is under the same preparation condition,the onset overpotential decreased from 304 mV to 132 mV.When the cathode current density is 10 mA/cm2,its overpotential is 244 mV.At the same time,the tafel slope of the catalyst was almost 82.6 mV/dec,which is lower than 103.8 mV/dec of the bulk MoS2.It was found that the stability of MoS2/AOCF catalytic material was still good after cyclic stability test,the performance of CV was still stable after 1000 cycles,and the time current curve of 10 h was also very stable.The results of electrochemical impedance test showed that the Rct resistance of MoS2/AOCF catalytic material was about 700 Ohm,while the Rct of bulk MoS2 reached over 1000 Ohm.The result of the double-layer capacitance test shows that the fitting slope of the double-layer capacitance of MoS2/AOCF catalytic material is 1.323,and that of the double-layer capacitance of MoS2 powder is 0.216.The results showed that the number of active sites of MoS2/AOCF was 6.1 times that of bulk MoS2.(2)Study on doping optimization of MoS2/AOCF catalytic materials.The optimal preparation conditions of Fe-doped MoS2/AOCF catalytic materials were as follows:sodium molybdate,thioacetamide,and ferric nitrate hydrate were 1.0 mmol,10.0 mmol,and 0.08 mmol respectively.The reaction temperature was 130?.The reaction time was 10 h.The optimal preparation conditions of Co-doped MoS2/AOCF catalytic materials were as follows:the dosage of sodium molybdate dihydrate was 1.0 mmol,the dosage of thioacetamide was 10.0 mmol,and the dosage of cobalt nitrate hexahydrate was 0.15 mmol.The reaction temperature was 130?.The reaction time was 12 h.The optimal preparation conditions for Ni-doped MoS2/AOCF catalytic materials were as follows:sodium molybdate,sodium thioacetamide and nickel hexahydrate were 1.0 mmol,10.0 mmol,and 0.05 mmol respectively.The reaction temperature was 130?.The reaction time was 12 h.Compared with the MoS2/AOCF catalytic materials without metal element doping,the electrocatalytic performance of the MoS2/AOCF catalytic materials doped with Fe,Co and Ni has been significantly improved.When the cathode current density was 10 mA/cm2,the overpotential of the three catalytic materials was 190 mV,169 mV and 145 mV,respectively.The results of electrochemical impedance tests showed that the Rct resistances of the three catalytic materials were?300 Ohm,?250 Ohm and?200 Ohm,respectively.(3)Investigation on carbonization process of MoS2/AOCF catalytic materials.The best preparation conditions for:AOCF was heated to 250 ? for 20 min within tinfoil.The dosage of sodium molybdate dihydrate and thioacetamide was 1.0 mmol and 10.0 mmol respectively.The reaction temperature was 130?.The reaction time was 12 h.When the cathode current density is 10 mA/cm2,the overpotential of the optimal MoS2/AoCF-C electric catalyst is 226 mV.It is obviously superior to the electrocatalytic properties of MoS2/AoCF catalytic materials in the chapter 2.