Effects of Ni, Fe, Cu, and Cr substitutions for Co in La0.8Sr0.2CoO3 on electrocatalytic properties for oxygen evolution

Abstract

The influence of some transition metal ion substitutions in the active 0.2 mole strontium-doped lanthanum cobaltate (La0.8Sr0.2Co1-yByO3 with B = Ni, Fe, Cu, and Cr; 0.1 ≤ y ≤ 0.4) lattice was studied on the electrocatalytic properties of the oxide by cyclic voltammetry and Tafel polarization techniques. The cyclic voltammetry showed a pair of redox peaks prior to the onset of oxygen evolution, regardless of the nature of the substitution. The presence of Fe or Ni, in small quantities, enhanced the electrochemically active area. The anodic polarization studies indicated two Tafel slopes: ∼2.3 RT/F at low and ∼2(2.3 RT/F) at high overpotentials. The oxygen evolution reaction on each B-site substituted perovskite followed first-order kinetics with respect to OH- ion concentration. The La0.8Sr0.2Co0.9Fe0.1O3 and La0.8Sr0.2Co0.9Ni0.1O3 electrodes showed the highest electrocatalytic activity based on geometrical surface area. Copper and chromium substitutions had detrimental effects on the electrocatalytic activity.