Cathodic behaviour of RuO2-doped Ni/Co3O4 electrodes in alkaline solutions:: hydrogen evolution

RuO2-doped Co3O4 electrodes were prepared by thermal decomposition of the corresponding nitrates using Ni as a support. The RuO2 content was varied between 0 and 20 mol %. The kinetics of hydrogen evolution from alkaline solution was studied by recording quasisteady state polarization curves at several NaOH concentrations. A mechanism is proposed on the basis of Tafel slopes and reaction orders. The electrocatalytic activity of the mixed oxides has been found to go through a maximum at intermediate RuO2 contents. Some evidence of instability has emerged.