Preparation Of Transition Metal Sulfide And Study On Their Electrocatalytic Oxygen Evolution Reaction Performance

Noble metal catalysts(IrO2,RuO2,etc.)are the most widely used catalysts for electrolytic water anodes.However,these catalysts have the problems of high cost and poor stability,which can not be further industrialized research and development and mass production.It is of paramount importance to craft non-noble metal catalysts with remarkable catalytic activity and robust stability by sophisticated methods to advance the widespread use of electrolytic water in reality.This thesis seeks to investigate transition metal sulfide,a widely used electrocatalyst for oxygen evolution reaction(OER).Physical characterization techniques were utilized to analyze the catalyst’s morphology and structure,and the electrocatalytic oxygen evolution performance of the catalyst was evaluated through the combination of the corresponding electrochemical testing and the practical application of the catalyst.The following are the research contents:(1)A kind of amorphous FeCoNi-S electrocatalyst was prepared by hydrothermal vulcanization of FeCoNi-OH with thioacetamide as raw material.The bifunctional catalytic capacity of the optimized catalyst for water splitting in alkaline electrolyte is higher than that of FeCoNi-OH.Considering the low intrinsic activity of FeCoNi-OH,its high bifunctional catalytic capacity should be derived from the hypervalent active sites of metal-sulfur species and newly formed high value metal-oxide species.In this case,an overpotential of only 280 mV and 80 mV is required for OER and HER when reaching 10 mA cm-2,respectively.For total hydrolysis,only 1.55 V voltage is needed to achieve this current density.(2)Co doped CuS/Graphene(Co-CuS/G)catalysts have been prepared by one step hydrothermal method.It is found that reasonable Co doping not only changes the morphology and electronic structure of CuS/G catalyst,but also increases the number of active sites.Nanosheet assembly structures offer the structural advantages of high surface area,short charge transfer paths,and easy access to active sites.In addition,highly conductive graphene facilitates the transfer of electrons between the active site and the electrode.In particular,in the Co1.0-CuS/G catalyst prepared with 1 mmol CoCl2·6H2O,a large number of CuS nanosheets were fixed on the graphene surface and formed porous structures and S-vacancy.Based on these advantages,Co1.0-CuS/G catalyst has significant catalytic activity against OER.Tests show that the current density of Co1.0-CuS/G can reach the standard 10 mA cm’2 at a low overpotential of 230 mV,and it has excellent durability(with a small performance decline after 5000 cycles).(3)Co-doped pyrite FeS2 nanospheres and Graphene composite catalyst(Co-FeS2/G)have been prepared by one-step hydrothermal method for OER in alkaline solutions.The electrochemical test results show that Co doped FeS2/G has better electrocatalytic performance than pure FeS2.The Co0.6-FeS2/G catalyst prepared with 0.6 mmol CoSO4·7H2O showed a unique nanostructure.The incorporation of Co can promote the electronic interaction within the catalyst,thus improving the efficiency and activity of the catalytic reaction.The amorphous hydroxide formed in situ not only acts as the real active site,but also inhibits the catalyst on the glassy carbon electrode from dissolving into the solution,leaving most of the active substance in the electrode.When the current density is 10 mA cm-1,the overpotential drops to 210 mV,and the Tafel slope is only 30 mV dec-1.(4)A one-step hydrothermal method was used to prepare Co doped MoS2/Graphene as a noble metal free OER electrocatalyst(Co-MoS2/G).Especially the Co0.6-MoS2/G catalyst prepared with 0.6 mmol Co(NO3)2·6H2O,the optimized Co0.6-MoS2/G catalyst has good OER performance,good stability at 5000 cycles,and negligible current loss.The excellent OER activity results from the co-modulation of MoS2 and Co structurally and electronically,and a good balance between the active site and the electronic conductivity.In addition,Graphene significantly improved the electrical conductivity of Co0.6-MoS2/G composites.It showed the best OER catalytic activity in 1.0 M KOH electrolyte,requiring only 220 mV overpotential at 10 mA cm-2.