(Invited) Optimizing Iridium Utilization for Oxygen Evolution Reaction – Viability of the Supported Ir Oxide Nanoparticles Strategy

Abstract

Determining the relationships between structure, oxidation state and oxygen evolution reaction (OER) activity is fundamental to design improved anode catalysts for polymer electrolyte membrane water electrolyser (PEMWE) devices. To date, Ir-based electrocatalysts are the best compromise between activity and stability. According to the scarcity of Ir on the Earth crust, the deployment of PEMWE technology cannot overlook an optimized utilization of Ir loading. Following the successful approach in proton-exchange membrane fuel cells (PEMFC) consisting of using carbon-supported Pt nanoparticles instead of Pt-blacks, we investigated supported Ir oxide nanoparticles. The nature of the support appears to be crucial since high-surface area carbon supports are rapidly degraded in the operating conditions of a PEMWE anode (E > 1.6 V vs. the reversible hydrogen electrode, T = 80 °C). We opted for alternative support materials based on doped tin oxide. In this contribution, a wide and sound library of Ir oxide materials differing from each other by the presence/absence of support and by the Ir architecture has been studied by identical location transmission electron microscopy, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometry and electrochemical techniques (Figure 1). It allowed us to establish trends on the viability of supported Ir oxide catalysts in the harsh PEMWE operating conditions [1].[1] F. Claudel, L. Dubau, G. Berthomé, L. Sola-Hernandez, C. Beauger, L. Piccolo, F. Maillard, ACS catal., 2019, 9 (5), 4688–4698.