Preparation Of Non-precious Nickel-cobalt-based Composite Electrocatalysts And Their Performances For Electrocatalytic Water Splitting

In recent years,global climate change and energy crisis have become issues faced by human being,with the rapid consumption of fossil fuels.Therefore,it is necessary to find a sustainable,efficient and clean energy to replace fossil fuels.At present,hydrogen energy is regarded as a promising option,which can be obtained by simaple water electrolysis.The electrochemical decomposition of water can be divided into two–half reactions:the hydrogen evolution reaction（HER）on the cathode and the oxygen evolution reaction（OER）on the anode.However,OER and HER usually require a large potential to drive electrochemical water splitting,resulting in high cost and low efficiency of water splitting.Although precious metal catalysts can improve the efficiency of water splitting,they are expensive and cannot be used on a large scale.Therefore,finding a cheap and efficient non-precious metal electrocatalyst that can be used for HER and OER is of great significance for improving energy efficiency.At present,among the first transition group metals,the eighth group nickel,cobalt-based catalysts are widely used due to the advantages of low cost and high performance in alkaline solutions.In this dissertation,non-noble metals are introduced into nickel,cobalt-based electrocatalyststo improve their ability and efficiency of water splitting.The main contents are as follows:1.Nickel-based MOFs（Mox-Ni-BTC）with different amounts of molybdenum contents were synthesized by a solvothermal method,which were then used as precursors for the synthesis of Mox-NiS₂ under microwave vulcanization.The morphology,composition and phase structures were analyzed by scanning electron microscopy（SEM）,X-ray diffraction（XRD）and X-ray photoelectron spectroscopy（XPS）and other test methods.The performance for HER was tested in an electrolyte solution of 1.0 M KOH.The results show that Mo_0.2-NiS₂ exhibits the best electrochemical activity.Its overpotential at 20 mA cm^-22 is 273 mV,and the corresponding Tafel slope is as low as 109 mV dec^-1.The introduction of an appropriate amount of Mo has a significant optimization effect on the electrocatalytic HER kinetics of Ni S₂.2.The glycerate salts(Ce_XCo_1-X-Gly)with different proportions of cobalt and cerium were synthesized by solvothermalmethod.By calcining the metal glycerates,the Ce_YCo_1-YO_X were obtained.The morphology,phase analysis and OER performance test were carried out.In the electrolyte solution of 1.0 M KOH,the overpotential of the catalyst Ce_0.15Co_0.85O_X at a current density of 10 mA cm^-22 is 330 mV and is lower than other Ce_YCo_1-YO_X,showing the best electrochemical performance.The experimental results confirm the synergistic effect between Ce species and Co3O4,and the introduction of Ce can improve the OER electrocatalytic performance of Co₃O₄.3.Nickel-cobalt alginate gels with different nickel-cobalt ratios were obtained by ion polymerization.By calcining the alginate gels,the nickel-cobalt/carbon aerogels were obtained.The OER performance was tested in an electrolyte solution of 1.0 M KOH.Among the nickel-cobalt/carbon aerogels obtained by different nickel-cobalt ratios,the catalyst with the nickel-cobalt mass ratio of 1:1 shows best OER performance.It can be seen that the synergistic electronic effect between nickel and cobalt can improve the electrochemical OER performance under certain conditions.