EFFECTS OF NI, FE, CU, AND CR SUBSTITUTIONS FOR CO IN LA0.8SR0.2COO3 ON ELECTROCATALYTIC PROPERTIES FOR OXYGEN EVOLUTION

The influence of some transition metal ion substitutions in the active 0.2 mole strontium-doped lanthanum cobaltate (La0.8Sr0.2Co1-yByO3 wit h B = Ni, Fe, Cu, and Cr; 0.1 less than or equal to y less than or equ al to 0.4) lattice was studied on the electrocatalytic properties of t he 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 pr esence of Fe or Ni, in small quantities, enhanced the electrochemicall y active area. The anodic polarization studies indicated two Tafel slo pes: similar to 2.3 RT/F at low and similar to 2(2.3 RT/F) at high ove rpotentials. The oxygen evolution reaction on each B-site substituted perovskite followed first-order kinetics with respect to OH- ion conce ntration. The La0.8Sr0.2Co0.9Fe0.1O3 and La0.8Sr0.2Co0.9Ni0.1O3 electr odes showed the highest electrocatalytic activity based on geometrical surface area. Copper and chromium substitutions had detrimental effec ts on the electrocatalytic activity.