Enhanced Oxygen Evolution Reaction Activity of a Cerium Oxide-Modified Lanthanum Manganese Oxide Perovskite Catalyst in an Anion Exchange Membrane Water Electrolyzer.

Abstract

There has been significant interest in the development of oxygen evolution reaction (OER) catalysts without the use of precious metals, in order to reduce the cost of electrolyzers for green hydrogen production. Herein, different weights (up to 20%) of CeO₂ added to lanthanum manganese perovskite oxide were synthesized by using the sol-gel method, followed by calcination at 900 °C in air. The phase purity of the prepared CeO₂-lanthanum manganese perovskite oxide electrocatalysts were investigated by using X-ray diffraction (XRD), followed by Rietveld analysis. The results confirmed that only perovskite and CeO₂ phases were present without extra impurity phases. An iodometric titration technique was employed to determine the chemical formula and the average oxidation state of Mn in the prepared electrocatalysts. The optimized electrocatalyst containing ∼10 wt % of CeO₂ content with lanthanum manganese perovskite (LCM-0.1) showed improved OER activity, achieving a greater than 22-fold increase in generated current density at 1.9 V versus RHE (reversible hydrogen electrode) in 0.1 M KOH compared to pure LaMnO₃. The electrocatalysts were tracked via in-operando Raman spectroscopy and ex-situ XPS spectroscopy, which evidenced reconstruction of the catalyst surface. The seen electrocatalytic activity improvement has been attributed to restructuring of the catalyst surface to form the MnOOH structure. A water electrolyzer was fabricated using the optimized LCM-0.1 electrocatalyst, and the device performance was evaluated with different loadings of the LCM-0.1 catalyst in the anode. The results suggest that the incorporation of cerium oxide in perovskite-based catalysts can be utilized as a method to promote OER electrocatalytic activity.