Synthesis of (La, Sr)CoO3 perovskite films via a sol–gel route and their physicochemical and electrochemical surface characterization for anode application in alkaline water electrolysis

Abstract

Physicochemical and electrocatalytic properties of perovskite-type La_{1 –x}Sr_xCoO₃(x= 0, 0.1, 0.2, 0.3, 0.5) synthesized by a low-temperature sol–gel process have been studied. Films were p-type semiconducting with a flat-band potential of approximately 0.30 V (Hg/HgO/1 mol dm^–3 KOH). The cyclic voltammogram between 0 and 0.65 V exhibited a pair of redox peaks (E⁰= 0.43 V) prior to the onset of O₂ evolution at the oxide film in 1 mol dm^–3 KOH. Among the oxide catalysts prepared, La_0.7Sr_0.3CoO₃ was the most active electrocatalytically. The Tafel slope and the reaction order for electrolytic evolution of oxygen were found to be 65–72 mV decade^–1 and ca. 1, respectively. Strontium substitution for La in the mixed-oxide lattice enhanced the electrochemically active area; the effect being greatest with 0.3 mol strontium.