Preparation And Electrocatalytic Oxygen Evolution Of Self-Supported Cobalt-Based Hydroxides

Electrocatalytic water splitting to produce hydrogen is one of the effective means to realize the economic cycle of hydrogen and to solve environmental pollution and energy problems.The development of non-precious metal catalysts with abundant reserves,low price,high efficiency and stability is essential to the development of sustainable energy.In recent years,cobalt-based hydroxides have received extensive attention as high-efficiency electrolysis water catalysts due to their advantages such as large specific surface area,easy synthesis,good electrical conductivity and hydrophilicity.On this basis,the electronic structure of the catalyst can be optimized and the binding energy of the active intermediate and adjusted through the adjustment methods such as heteroatom doping,defects,strain,and interface engineering,thereby improving the electrocatalytic performance of the material.Therefore,this paper designed and synthesized Co（OH）₂nanostructures with different phases（α-Co（OH）₂/NF,β-Co（OH）₂/NF,Co₂（OH）₃Cl/NF and mixed phaseα-Co（OH）₂/Co₂（OH）₃Cl/NF）,and further we optimized the catalytic performance ofα-Co（OH）₂/NF by alkali etching,and in-depth analysis of the related catalytic mechanism and a series of material electrocatalysis,in conclusion there are internal factors for the difference in performance.A simple solvothermal method was used to prepare Co（OH）₂/NF composites with a three-dimensional structure.Among them,the mixed phaseα-Co（OH）₂/Co₂（OH）₃Cl/NF showed excellent performance in alkaline electrolytes.With its oxygen evolution performance,a current density of 50 m A cm^-2 can be reached with an overpotential of 304 m V,and the Tafel slope is 104 m V dec^-1.In addition,α-Co（OH）₂/Co₂（OH）₃Cl/NF is used as a dual-function catalyst for complete water dissolution,a low battery voltage of 1.62 V can reach a current density of 10m A cm^-2 and it shows excellent stability and durability.During the OER reaction,the mixed-phaseα-Co（OH）₂/Co₂（OH）₃Cl/NF sample is transformed into the real catalytically active substanceγ-Co OOH,which promotes the electron transfer between the cobalt ion and the reaction intermediate OOH^*,has excellent catalytic performance.Although the catalyst has undergone a material transformation in the OER test,its morphology and structural integrity are still maintained well.The electrocatalytic performance of α-Co（OH）₂/NF was further optimized by alkali etching,and E-α-Co（OH）₂/NF with porous structure was obtained.The oxygen vacancy adjustment occurred during the pore making process,electronic structure of E-α-Co（OH）₂/NF is improved,give it abundant active sites and good conductivity.The OER performance of the catalyst was further regulated by adjusting the alkali etching concentration and reaction time.The OER performance of the sample reacted in 0.5 mol L^-1 KOH solution for 2 h was the best,and the required overpotential was only 275 m V at a current density of 50 m A cm^-2,the Tafel slope is as low as 72 m V dec^-1.After 20 hours of long-term stability,the test voltage did not drop significantly,showing good durability.