Preparation And Properties Investigation Of Novel Electrocatalysts For Water Splitting Based On Cobalt-molybdenum

Hydrogen（H₂）with non-polluting and high energy is an ideal energy carrier to replace traditional fossil fuels.Electrocatalytic water splitting is an effective way to produce hydrogen,but the high energy barrier of water splitting will lead to extra cost.It is necessary to develop efficient electrocatalysts for electrocatalytic water splitting.Noble metal-based catalysts（Pt,Ir O₂etc.）exhibit excellent electrocatalytic performance for HER and OER,but the scarcity and high cost limit their industrial application.Transition metal compounds have attracted extensive attention because of their high earth-abundance,low-cost and excellent performance in electrocatalytic water splitting.Molybdenum compounds and cobalt compounds are good of HER and OER catalytic.In this thesis,two cobalt-molybdenum based compounds were synthesized by hydrothermal reaction and high temperature annealing.Then their physicochemical properties and electrocatalytic performance were studied.The research contents of this thesis are as follows:（1）Preparation,characterization and testing of Co Mo S_x/NF materials:First,Co₃O₄nanosheets were prepared on nickel foam by hydrothermal reaction,and then Co/Co₂Mo₃O₈/NF nanosheets subjected to heat treatment under reduction condition（Ar/H₂）.Finally,Co Mo S_x/NF nanosheets were prepared by sulfurization with sublimed sulfur.At a current density of 10 m A cm^-2 in 1.0 M KOH,the overpotential required for HER and OER of Co Mo S_x/NF were 39.2 m V and270 m V,respectively.There were four reasons for the high activity of the catalyst:Firstly,nickel foam improves the electrical conductivity and mass transfer efficiency of the catalyst.Secondly,the nanosheet array enables the catalyst to have a larger electrochemical surface area and expose more active sites.Thirdly,Co Mo S_x/NF has many unsaturated sites due to its long range disordered,which increases the variety of active sites.Fourthly,the interaction between cobalt and sulfur leads to the redistribution of electron and adjusts the adsorption free energy.（2）Preparation,characterization and testing of Mo O₂@Co₃O₄/NF materials:First,Co₃O₄nanorods were prepared on nickel foam by hydrothermal reaction,and then Mo O₂ particles were electrodeposited on Co₃O₄ nanorods.Finally,Mo O₂@Co₃O₄/NF nanorods were obtained by heat treatment under inert gas.At a current density of 10 m A cm^-2 in 1.0 M KOH,the overpotential required for HER and OER of Mo O₂@Co₃O₄/NF were 60 m V and 250 m V,respectively.There were three reasons for the high activity of the catalyst.Firstly,nickel foam improves the electrical conductivity and mass transfer efficiency of the catalyst.Secondly,the nanorod array increase the electrochemical surface area and expose more active sites.Thirdly,the different electronegativity of cobalt,molybdenum and oxygen leads to electron redistribution to forming electron-rich Mo O₂species and electron-poor Co₃O₄ species,which adjust the adsorption free energy.There are 31 figures,3 tables and 82 references in this thesis.