Study On The Preparation And Electrocatalytic Performance Of Cobalt(nickel)-based Metal Oxides

Electrochemical water separation technology is a clean and sustainable hydrogen power generation technology that can replace traditional fossil fuels.This is of great significance to the development of renewable energy,the alleviation of energy crisis and the improvement of environmental problems.Oxygen evolution reaction（OER）and hydrogen evolution reaction（HER）,as two half reactions,are slow electron transfer reactions in terms of kinetics,and improving the electron transfer efficiency in electrocatalysis is a major challenge in the field of electrochemical catalysis and energy storage.Therefore,the design of effective electrocatalyst to increase the efficiency of electron transfer is the key to reduce the overpotential and improve the efficiency of electrocatalysis.An effective electrocatalyst is needed to reduce its overpotential and improve energy conversion efficiency.At present,the high cost and rarity of precious metal electrodes such as Ru,Ir and Pt hinder their large-scale application in catalysts.Therefore,it is of great practical significance to develop non-noble metal and high efficiency electrocatalysts for OER and HER.So far,due to the high efficiency,low cost and abundant resources of transition metals（such as Co,Ni）of non-noble metals,they have attracted extensive attention as substitutes of noble metal catalysts for OER and HER.In this paper,cobalt（nickel）based oxide as the research object,provides a simple and novel preparation method,at the same time,the morphology and composition of cobalt（nickel）based oxide are characterized,and its electrochemical performance is tested and discussed.The specific research contents are as follows:1.The Multi-interface FeOOH@NiCo₂O₄hybrid nanoflowers were prepared by two-step hydrothermal reaction.The first step is to synthesize NiCo₂O₄nano-flowers by the hydrothermal method,which is calcined at 400°C as a precursor,and then the FeOOH nanoparticles are wrapped by the second step of hydrothermal method to form a heterogeneous structure.The prepared electrocatalyst can provide abundant electroactive sites and form FeOOH@NiCo₂O₄nano interface,which can also improve the charge transfer rate.The results showed that the prepared catalysts exhibited strong electrocatalytic properties under OER and HER conditions.In addition,in a two-electrode water diversion system,FeOOH@NiCo₂O₄heterostructure as a dual-function electrocatalyst requires only 1.58 V battery voltage at a current density of 10 m A cm^-2,and it also has excellent cycle stability.2.We have prepared three-dimensional spherical Ni（OH）₂@NiCo₂O₄heterojunction by one-step hydrothermal method.By adjusting the Ni/Co atomic ratio of the heterojunction,we have studied their high-efficiency electrocatalysts for oxygen evolution and hydrogen evolution in alkaline electrolytes.Among them,the optimized Ni（OH）₂@NiCo₂O₄has high electrocatalytic activity.At 10 m A cm^-2,the overpotentials corresponding to OER and HER are 215 m V and 189 m V,respectively.The improvement of the catalytic performance of Ni（OH）₂@NiCo₂O₄heterojunction is attributed to the chemical synergistic combination of Ni（OH）₂and NiCo₂O₄,the exposure of more accessible active sites and the activation of heterogeneous interfaces of intermediates that promote electron/electrolyte transport.3.Fe₂O₃@Ni（OH）₂heterojunction material is prepared by a simple hydrothermal method,and then calcined in air at high temperature to oxidize Ni（OH）₂to Ni O,and finally Fe₂O₃@Ni O is obtained.The oxygen vacancies in Fe₂O₃@Ni O can effectively improve the efficiency of charge separation and interface charge transfer.In 1.0 M KOH alkaline electrolyte,the OER and HER processes exhibit low overpotentials of 224 m V and 187 m V,and low Tafel slopes at a current density of 10 m A cm^-2.Compared with pure Ni O and Fe₂O₃,it shows better catalytic performance and stability.