Anodically electrodeposited Co+Ni mixed oxide electrode: preparation and electrocatalytic activity for oxygen evolution in alkaline media

Abstract

Co+Ni mixed oxides on Ni substrate were prepared through anodic electrodeposition from Co(NO3)2 and Ni(NO3)2 aqueous solutions with five different Co2+/Ni2+ ratios beside only Co2+. By the electrochemical measurements, the optimum performance in electrocatalytic activity for oxygen evolution reaction in alkaline media was obtained on the Co+Ni mixed oxide deposited from the solution containing Co2+/Ni2+ ratio of 1:1. The mixed oxide is corresponding to about 68at% Co contents with spinel-type NiCo2O4 phase and porosity surface structure. The electrochemical kinetic parameters including exchange current density, Tafel slopes, reaction order with respect to [OH−] and standard electrochemical enthalpy of activation were analyzed also. A possible mechanism involving the formation of a physisorbed hydrogen peroxide intermediate in a slow electrochemical step was presented, which accounts for the values of the experimental results.