Preparation And Properties Of Transition Metal Compounds As Oxygen Evolution Electrocatalysts

Oxygen evolution reaction(OER)is one of a slow kinetic process in electrocatalytic cracking.It has been proven that precious metal catalysts,such as IrO2 and RuO2,are one of the most effective catalysts for OER.However,precious metal catalysts,with high cost and poor long-term stability,is rare in earth,which hinder their development and widespread application to a large extent.Therefore,it is meaningful to develop new catalysts with high electrocatalytic activity,excellent durability,and sufficient global coverage.In this thesis,we studied about the catalytic performance of Fe-doped NiCoP porous nanoplatelet arrays,3D Ni4Fei1.2-LDH hydrangea nanostructures as well as the effect of Fe-doped NiCoS nanomaterials to oxygen evolution catalyst.Through a series of characterization methods and test,specific studies have been conducted on the corresponding catalyst materials:(1)The catalytic Fe-doped NiCoP nanosheet arrays(NiCoFeP)in situ grew on the nickel foam via a simple and mild method combined hydrothermal treatment with phosphorization.The unique nanosheet array structure and ability of fast electron transport,Ni,Co and P are active sites in catalysts as well as the synergetic effects among those four elements,all benefit for catalysts reaction.The study concluded that after doping with Fe,the as-prepared NiCoFeP/NF with 7%Fe shows the best OER performance.When the electric potential is below 271 mV,it achieves a current density of 200 mA·mc-2 and shows a small Tafel slope of 45 mv·dec-1 in 1 M KOH solution.(2)The catalytic Ni4Fe1.2-LDH/NF hydrangea macrophylla in situ grew on the nickel foam via a simple and mild method combined hydrothermal treatment.It mainly studied different molar ratios of Ni and Fe and the different hydrothermal temperature.The results show that when the hydrothermal temperature Is 100? and the Ni:Fe is 4:1.2,catalytics are at their best performance.When overpotential is 258 mV electricity current density can reach 100 mA/cm2 and shows a small Tafel slope of 20 mV/dec in 1 M KOH solution which attribute to the unique 3D hydrangea macrophylla nanostructure and the synergetic effects among Fe,Ni elements.Therefore,the as-prepared Ni4Fe1.2-LDH/NF is a low-cost,high efficient,robust stable competent catalyst for the oxygen evolution.(3)The research,putting different percentage of Fe into NiCoS catalyst with hydrothermal method,dissussed the effects of different percentages of Fe doping and different amounts of sulfur sources on the oxygen evolution of electrocatalytic cracking catalytic by hydrothermal treatment.The results show that the best catalytic performance is obtained when the percentages of Fe is 5%and the amounts of sulfur sources is 500 mg.With a low overpotential of 365 mV,it achieves a current density of 10 mA/cm2 in 1 M KoH solution.It probably the result of Ni,Co,Fe and S as active site,and the synegistic effect among them and graded porous structure of the prepared material promoting the full contact between the catalyst and the electrolyte.Those are favorable for the OER reaction.