Preparation Of Nickel-based Electrocatalysts And Study On Their Water Electrolysis Properties

Hydrogen is considered to be the most ideal form of energy due to its high energy density and cleanliness,water electrolysis is one of the effective ways ot obtain hydrogen,it contains hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).However,the reaction efficiency is not high because of the high energy barrier,Thus,it is desirable to find low cost electrocatalysts which are catalytically active for both HER and OER.Transition metal based catalysts have the characteristics of abundant reserves and good catalytic activity,especially nickel-based catalysts have received extensive attention in recent years.In this paper,the three-dimensional nanocomposite structure and metal doping are used to improve the HER and OER activities of nickel-based eletrocatalysts,thereby improving the effiency of water splitting.The research contents are as follows:1.Using the nickel foam as a carrier,a three-dimensional composite structure of Co9S8 Nanowires@NiCo LDH Nanosheets was constructed by hydrothermal reaction.Ultra-thin NiCo LDH nanosheets can expose more reactive sites,and the combination with Co9S8 nanowires can greatly increasing the specific surface area of the the catalyst,the synergistic effect of components can largely increase the catalytic performance.Compared with pure Co9S8 and NiCo LDH,this composite structure exhibits superior catalytic performance for both HER and OER.In the 1 M KOH solution,for the hydrogen evolution reaction,when the current density reach 10 mA/cm2,the required overpotential is 168 mV.For the oxygen evolution reaction,it requires 278 mV to reach 30 mA/cm2.When used as both anode and cathode in a two-electrode system,the electrode can achieve current densities of 10 mA/cm2 at a low cell voltage of 1.63 V,and shows good structural stability at the same time,proving the material as superior bifunctional catalyst for water splitting.2.With nickel foam as the nickel source and ammonium molybdate as the molybdenum source,NiMoO4·xH2O nanoarrays with two different morphologies of cuboidal and rod-shaped were obtained by adjusting the temperature of the hydrothermal reaction and the concentration of the reactants.A vapor deposition reaction was carried out at 400? with sodium hypophosphite as a phosphorus source,both two morphologies were retained after phosphating reaction.The electrochemical activity test shows that the catalytic activity of the rod-like structure was better than that of the cuboid structure,the NiMoO4·XH2O/NF changed into Mo-Ni2P/NF by XRD test,it shows significant improvement in catalytic activity compared with Ni2P toward both HER and OER.To reach current density of 10 mA/cm2,it requires 131 mV in alkaline solution and 142 mV in acidic solution for HER,and 270 mV in alkaline solution for OER.When the material is used to electrolyze water,a current density of 1.67 V is required to reach 10 mA/cm2.