Design Of The Nickel-based Chalcogenide Composite Catalysts And Their Performance For Oxygen Evolution Reaction

The development of clean and renewable energy sources is urgent to addresss the environmental issues and energy crisis.Hydrogen has attracted intensive attention due to the advantages of high energy density and cleaness.Water splitting into oxygen and hydrogen is a promising alternative route,which is drived by electric energy from renewable energy resources.However,the oxygen evolution reaction?OER?on the anode always requires high overpotentials to drive this reaction due to its slow kinetics.Currently,Ir-,Ru-based compounds are considered as the high-efficiency OER electrocatalysts,but low earth abundance and high cost hinder their widespread applications.It is thus imperative to develop highly efficient catalysts based on earth-abundant elements for the electrolysis of water.Great efforts have been devoted to develop transition-metal-based catalysts for OER in alkaline electrolyte due to their earth abundance.Rencently,it has been found that Ni-based compounds and their derivatives exhibit excellent catalytic activity than noble metals in OER.In this thesis,Ni-based catalysts are prepared as the efficient OER catalysts by doping metal and non-metal elements to modify the morphology and the interaction among the compounds.The main work contents are as follows:?1?The hollow Ni-based chalcogenides?denoted as Ni S_xSe_y?were synthesized by a facile low-temperature calcination process of Ni-based acetate hydroxides to introduce sulfur and selenium.Besides,Ni S_xSe_y with various ratio of S to Se were prepared as counterparts.The prism structure was transformed to a hollow structure due to the Kendall effect after low temperature calcination,which can expose more active sites,and thus improve the OER performance.Due to the strong interaction of Ni S₂ and Ni Se₂,the optimal Ni S₃Se₂ exhibits excellent OER activity and stability,which only requires the overpotential of 291 m V to reach a current density of 20 m A cm^-2.?2?Ultrathin nickel-iron carbonate hydroxides nanosheets/sulfides with bimodal mesopore?denoted as Ni_xFe_yS/CH?were fabricated by sulfurizing treatment of nickel-iron carbonate hydroxide?Ni_xFe_yCH?.The partial sulfuration of Ni Fe carbonate hydroxides by replacing the CO₃/OH groups with the S group could well remain the hexagonal morphology,regulate the electronic structure and expose more electrochemical active sites.Benefiting from the ultrathin-layered structure with mesopore for more available active sites,the strong interaction between metal carbonate hydroxides/sulfides,as well as bimetal synergism for modulation the composition and electronic structure,the optimal Ni_xFe_yS/CH exhibits excellent OER catalytic performance,which reaches 20 m A cm^-2 at an ultra-small overpotential of 261 m V,lower Tafel slope(103 m V dec^-1)and outstanding stability.