Abstract
Lanthanum cobaltate and its strontium-substituted products have been prepared using a novel stearic acid sol–gel method at 600 °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 ≅ 65 mV/decade) at low and the other ( b 2 ≅ 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 ( Δ H # 0 ) and standard entropy of activation ( Δ S # 0 ) were ∼ 126 kJ mol - 1 and ∼ 112 J deg - 1 mol - 1 and ∼ 109 kJ mol - 1 and ∼ 144 J deg - 1 mol - 1 on the base oxide and La 0.6Sr 0.4CoO 3, respectively.
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