The Preparation Of Metal Oxide Heterojunction And The Study Of Their Electrocatalytic Oxygen Evolution Performance

Hydrogen,which possesses high mass energy density and carbon-free emissions,has been considered as an ideal,sustainable and clean energy.Electrocatalytic water splitting is an efficient approach to obtain high-purity hydrogen.Nonetheless,due to the relatively sluggish kinetics and higher overpotentials of oxygen evolution reaction（OER）,the practically wide application of water splitting has been greatly impeded.Therefore,exploration of high-efficient oxygen evolution electrocatalysts which can accelerate the reaction rate at low overpotentials and possess good stability still remains a great challenge.This study has focused on oxygen evolution reaction and two metal oxide heterojunction electrocatalysts have been developed.The studies are as follows:1.Herein,a novel nanocomposite of Co₃O₄/CeO₂ heterojunction was developed for highly-efficient alkaline oxygen evolution reaction（OER）.Not only can the supported Co₃O₄nanoparticles（NPs）effectively improve the electron conductivity of composite（decrease the charge transfer resistance）,but also it increases the surface oxygen vacancy concentration and active oxygen species of CeO₂,which can be attributed to the partial electron transfer from Co₃O₄ NPs to CeO₂ surfaces.As a consequence,58.5%Co₃O₄/CeO₂（58.5%,mass ratio between Co₃O₄ and CeO₂）exhibits a better OER performance(a low overpotential of 347 m V at 10 mA cm^-2 and small Tafel slope of 72.7 m V dec^-1)along with an excellent stability as compared with the commercial RuO₂(an overpotential of 359 m V at 10 mA cm^-2).2.Herein,a FeOOH/NiCo₂O₄ heterojunction composite was developed for alkaline electrocatalytic oxygen evolution reaction.Due to the surface electronic interaction between FeOOH and NiCo₂O₄,the supported FeOOH nanoparticles（NPs）can not only effectively improve the electronic conductivity of the composite（decrease the charge transfer resistance）,but also increase the surface Co³⁺concentration of NiCo₂O₄(Co³⁺is generally deemed to be active sites for OER).As a consequence,FeOOH/NiCo₂O₄ composite exhibits a better oxygen evolution performance(a low overpotential of 308 m V at the current density of 10 mA cm^-2 and small Tafel slope of42.5 m V dec^-1)along with a good stability as compared with the commercial RuO₂(an overpotential of 359 mV at 10 mA cm^-2).