Electrocatalytic properties of perovskite-type La1-xSrxCoO3 (0 ≤ x ≤ 0.4) obtained by a novel stearic acid sol-gel method for electrocatalysis of O2 evolution in KOH solutions

Lanthanum cobaltate and its strontium-substituted products have been prepared using a novel stearic acid sol-gel method at 600 degrees C. The oxide catalysts followed the rhombohedral hexagonal crystal geometry. Sr-substitution (0.2-0.4 mol) increased the oxide roughness as well as the apparent electrocatalytic activity greatly. The oxygen evolution on each oxide catalyst showed two Tafel slopes, one (b(1) congruent to 65 mV/decade) at low and the other (b(2) congruent to 103 mV/decade) at higher overpotentials. The reaction order w. r. t. OH- concentration was approximately unity. Values of thermodynamic parameters for the oxygen evolution reaction (OER), namely, the standard enthalpy of activation (Delta H-#0) and standard entropy of activation (Delta S-#0) were similar to 126 U mol(-1) and similar to 112 J deg(-1) mol(-1) and similar to 109 kJ mol(-1) and similar to 144 J deg(-1) mol(-1) on the base oxide and La0.9Sr0.4CoO3, respectively. (c) 2004 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.