Electrochemical studies of a nickel–copper electrode for the oxygen evolution reaction (OER)

The electrochemical behavior of Ni-30 at% Cu electrode has been investigated in 30 wt% KOH electrolyte by cyclic voltammetry at 300 and 325 K. In the cyclic voltammograms, a couple of anodic and cathodic peaks have been observed. These peaks appeared for the electrochemical transformation of M(II) oxide ⇌M(III) oxide. With increasing cycling time, peak potentials continuously shifted to the cathodic direction and the peak currents increased remarkably. No steady-state voltammogram was appeared even after cycling up to 110 min. Increase in anodic peak current showed a gradual increase of current for the oxygen evolution reaction (OER). Compared with Ni electrode, remarkably low cathodic potentials for M(II) oxide ⇌M(III) oxide transformation and OER have been observed. Increase in temperature showed positive effects on peak currents and peak potentials for the OER, and oxygen evolution potential shifted to the cathodic direction. The Tafel plots showed two well-defined Tafel regions. The exchange current density (io) value increased remarkably and Tafel slope (b) value increased a little with increasing temperature. The observed io value and current density (i) showed a good performance of this electrode for OER over Cu, Co-20 at% Cu, NiCo2O4 and Ni electrodes.