Iridium-Based Perovskites as Efficient Oxygen Evolution Reaction Catalysts in Acid Media

Abstract

A series of perovskite-based catalysts were synthesized for oxygen evolution reactions (OERs), primarily intended for anodic reactions in the zinc electrowinning process. OER represents a significant portion of the energy consumption in the zinc electrowinning process, and our objective is to explore the possibility of using Ir-based perovskite catalysts to reduce this energy consumption. Ba–Ir perovskite was used as the starting point, and it was doped by other cations (M) to achieve BaM x Ir1–x O3 perovskites. Solid-state reaction (SSR) was employed to prepare the catalytic compounds. The crystalline structure of materials was investigated using X-ray diffraction (XRD). Potentiodynamic polarization and electrochemical galvanostatic tests were used to assess the performance of the synthesized materials with respect to the OER. Morphology and surface chemical composition of the optimized compound were evaluated, respectively, using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis methods. The results reported here show that, compared to the benchmark IrO2 catalyst, the catalytic performance of Ir in a perovskite structure was significantly improved, while its Ir content was substantially lower. However, the activity of these compounds in sulfuric acid media is reduced over time. We found that the main deactivation mechanism of the catalysts is related to the formation of the Ba sulfate on the catalyst. The deactivation rate is highly dependent on the doped cation (M). BaNb0.2Ir0.8O3, with 42% less iridium content, was found to be the best catalyst among the synthesized formulations, satisfying the requirements of catalytic activity and longevity in highly acidic environments.