Preparation Of Cobalt-based Nanocomposites And Performance For Alkaline Oxygen Evolution Reaction

The huge energy consumption and serious chemical pollution problems,which caused by the rapid development of manufacturing industry allover the world,bringing an urgent demand for developing green energy carriers and efficient power generation technology.Hydrogen is an ideal fuel,and electrochemical water splitting is widely regarded as an effective pathway for producing H₂.The anodic oxidation of water intrinsically is frustrated by the highly sluggish reaction kinetics,which demands rational water oxidation catalysts（WOCs）to lower the overpotential as well enhance the efficiency.So far,although Ir O₂and Ru O₂are the most commonly used for oxygen evolution reaction（OER）,the pratical application of them is awfully limited by the scarcity and high-cost.Therefore,the design of efficient and stable WOCs based on non-noble metal elements is the key to realize electrolytic water.Cobalt（Co）is perceived as an promising transition metal due to its great electrochemical water oxidation catalytic power and cobalt-related materials have been widely used as OER catalysts.This thesis,Cobalt-related materials have been synthetised by using nickel foam（NF）as substrate.Introducing non-noble metal elements Ni,Fe to improve catalytic activity and reduce overpotential by hydro-thermal process.The microstructure and OER performance in 1.0 M KOH solution have been studied in the thesis.The detailed research and results are as follows:（1）By two-step hydrothermal method,Co-based precursor was synthesized firstly and vulcanized with thioacetamide（TAA）as sulfur source,to obtain three-dimensional grass-like cobalt sulfide nickel sulfide（Co_xS_y-Ni_xS_y/NF）nanocomposites.In 1.0 M KOH solution,it requires an overpotential of 275 m V to approach a current density of10 m A/cm~2.（2）The precursor Co（OH）₂/NF was synthesized firstly by hydro-thermal process,then Co₃O₄was obtained by annealing the precursor,lastly introducing cobalt nickel layered double hydroxide（Co Ni-LDH）to prepare the three-dimensional Co₃O₄@Co Ni-LDH/NF core-shell nanosheet structure by hydro-thermal process.In 1.0M KOH solution,it requires an overpotential of 288 m V to approach a current density of 10 m A/cm~2.（3）Co-MOF nanosheet arrays grown in situ on NF were synthesized by one-step hydro-thermal process.This thesis reported the differences between MOF self-supporting catalyst and MOF powder catalyst.Moreover,Co Fe-MOF/NF material were preparated by doping Fe ion in one-step hydro-thermal process.Fe-doped affected their micro morphology and structure by changing ratio,improving the activity of OER.After testing electrochemical performances,it found out that showing the best OER performance when the ratio of Fe ion to Co ion was three to one.In 1.0 M KOH solution,it requires an overpotential of 218 m V to approach a current density of 10m A/cm~2,besides it has good stability.