Development And Performance Of CoCuP Catalysts For Water Oxidation

Energy shortages and environmental pollution have promoted the development of green energy technologies.Hydrogen,with the advantages of high combustion calorific value and environmental friendliness is an ideal energy carrier.Electrochemical water splitting is one of the effective technologies to produce hydrogen,which can convert sustainable electrical energy to green chemical energy.In practice,water splitting involves two half-reactions:hydrogen evolution reaction（HER）on the cathode and oxygen evolution reaction（OER）on the anode.Between this two half reaction,water oxidation is kinetic sluggish due to the four-proton and four-electron transfer processes.Therefore,development of low-cost,high-activity OER catalysts is the key to the large-scale water splitting.Precious metals（Ru,Ir）based materials show highly efficient activity for OER.However,the scarcity and high price of precious metals have limited their large-scale applications.Cobalt-based OER catalysts have been developed and utilized due to the advantages of abundant reserves,low cost,and excellent electrocatalytic properties.In the first part of the thesis,CoP and CoCuP electrodes were prepared by potentiodynamic deposition with copper foil as substrates.The surface morphology and composition of the as-prepared electrodes were characterized by scanning electron microscopy（SEM）,X-ray diffraction（XRD）,Inductively Coupled Plasma Optical Emission Spectrometer（ICP-OES）and X-ray Photoelectron Spectroscopy（XPS）.The results show that the electrochemically active surface area of CoCuP can be increased significantly under alkaline conditions.The electrocatalytic properties of CoP and CoCuP electrodes toward water oxidation were evaluated via the electrochemical tests.It reveals that CoCuP electrode shows better catalytic activity compared with CoP electrode in 1M KOH aqueous solution,achieved a current density of 10mA cm^-2 at the overpotential of 238 mV.In addition,CoCuP exhibits pH-dependent OER activity relative to RHE,indicating that the lattice oxygens participate in the OER reaction as active sites.The SEM images of CoCuP show a nanosheet accumulation structure with a high electrochemically active surface area（ECSA）.This phenomenon indicated that a further higher ECSA might be achieved with CoCuP as a support framework.Thus,CoCuP/CoP electrode was prepared through potentiodynamic deposition with CoCuP as substrates.The as-prepared electrode shows a catalytic current density of 10 mA cm^-2 at the overpotential of 143 mV in 1 M KOH aqueous solution.Furthermore,the durability of the CoCuP/CoP electrode for water oxidation was tested under alkaline conditions at the current density of 10 mA cm^-2.A constant overpotential of 230 mV was detected for 10 h,indicating that the as-prepared electrode is stable under applied conditions.