Properties Of Ni-based And Cobalt-based Electrocatalysts Modified By Cerium Oxide And Titanium Oxide

The excessive consumption of fossil resources and the consequent environmental pollution problems force us to develop and utilize renewable and clean energy alternative to fossil fuels.As a clean,efficient,safe and sustainable new energy source,hydrogen energy is regarded as the most promising clean energy in the 21st century.Hydrogen production from water electrolysis is an effective way to solve this predicament.However,the existence of overpotential during the electrolysis of water makes the high energy consumption of water electrolysis.Therefore,we need to develop a highly active hydrogen evolution reaction catalyst and an oxygen evolution reaction catalyst to reduce the overpotential of the water decomposition reaction,and thereby to improve energy conversion efficiency.However,the water electrolysis catalysts with the best catalytic activity so far are all precious metal materials,which are not conducive to large-scale industrial applications.Therefore,there is an urgent need to develop water electrolysis catalysts with low overpotential and abundant reserves on the earth to improve reaction kinetics and water electrolysis efficiency.Inthispaper,ahighperformanceoxygenevolutioncatalyst Ni?OH?₂·0.75H₂O@CeO₂ nanosheet and hydrogen evolution catalyst Co/Co₂P-TiO₂were synthesized by adding functional oxide?CeO₂,TiO₂?to the transition metal-based material.The main results are listed below:?1?we introduce a nickel hydroxide nanosheet incorporating CeO₂ by electrodeposition on carbon fiber paper as a highly efficient oxygen evolution reaction electrocatalyst,and its efficient catalytic performance in oxygen evolution reaction.Optimization experiments on the molar ratio of nickel to cerium in electrodeposition solution show that the film prepared by the ratio of nickel to cerium of 30:1 has the best electrocatalytic oxygen evolution performance.After the introduction of CeO₂,the optimized Ni?OH?₂·0.75H₂O@CeO₂ nanosheets shows a great enhancement in the oxygen evolution reaction performance compared to the Ni?OH?₂·0.75H₂O nanosheets deposited by the same method,of which the lowest overpotential is 320 mV at a current density of 100 mA cm^-2 in an alkaline electrolyte,and the Tafel slope is 126 mV dec^-1.At the same time,Ni?OH?₂·0.75H₂O@CeO₂ nanosheets have been shown to have good stability and up to 92%Faraday current efficiency during long-term water oxidation at high-reaction rate.?2?we introduce a Co/Co₂P mesoporous film decorated with TiO₂ on carbon fiber paper as a highly efficient hydrogen evolution reaction electrocatalyst,and its efficient catalytic performance in hydrogen evolution reaction.Low-temperature phosphating converts Co to Co₂P,and the hydrogen production performance of Co/Co₂P in alkaline media can be improved by TiO₂ loading.The Co/Co₂P-TiO₂ obtained by this method has an overpotential of 52 mV at a current density of 20 mA cm^-2 and an overpotential of 96 mV at a current density of 100 mA cm^-2,and the Tafel slope is 126 mV dec^-1,which is comparable to all reported performance of hydrogen evolution catalyst.At the same time,this Co/Co₂P-TiO₂ mesoporous film has been shown to have excellent long-term stability and up to 93%Faraday current efficiency during long-term water oxidation at high-reaction rate.