P-029

Leonard Moriau

leonard.moriau@ki.si

A. K. Surca, A. Logar, L. Suhadolnik, M. Bele, N. Hodnik

National Institute of Chemistry, Slovenia

Raman spectroscopy study of various iridium-based electrocatalyst for oxygen evolution reaction: impact of activation protocol and support

The hydrogen economy relies on the widespread commercialization of proton exchange membrane water electrolysis (PEMWE). However, the efficiency of PEMWE is limited by the oxygen evolution reaction (OER). Currently, iridium is the state-of-the-art OER catalyst, but its rarity and high cost pose significant challenges to the large-scale deployment of PEMWE. Understanding the mechanism of the OER, particularly the oxidation states of iridium, is crucial for optimizing catalyst performance, though some aspects remain debated [1]. Raman spectroscopy has emerged as a powerful tool to gain insights into the redox behavior of the Ir(III)/Ir(IV) transition and the OER process [2,3]. In this work, we apply both ex-situ [4] and in-situ Raman spectroscopy to explore iridium-based catalysts. 

We investigate commercial Ir-black and IrO2 to compare the effects of activation in different electrochemical windows, as well as iridium nanoparticles supported on Carbon and TiO2. Our results show that varying activation and degradation protocols lead to distinct Raman spectral features, which are closely linked to the oxidation state of iridium. This highlights the importance of activation protocols and their effect on the formed active sites for different catalysts. This work also demonstrates the potential of Raman spectroscopy to provide valuable insights into the oxidation states of iridium-based catalysts, even when supported on materials like Carbon and TiO2. Notably, the formation of iridium oxide from metallic iridium could be detected with Raman spectroscopy and compared to unsupported benchmarks.

References:

[1] Lončar, A.; Escalera-López, D.; Cherevko, S.; Hodnik, N. Inter-relationships between oxygen evolution and iridium dissolution mechanisms. Angew.Chemie – Int. Ed. 2022, 61, e202114437.

[2] Pavlovic, Z.; Ranjan, C.; Gao, Q; van Gastel, M.; Schlögl, R. Probing the structure of a water-oxidizing anodic iridium oxide catalyst using Raman spectroscopy. ACS Catalysis 2016, 6, 8098-8105.

[3] Saeed, K.H., Forster, M.; Li, J.F.; Hardwich, L.J.; Cowan, A.J. Water oxidation intermediates on iridium oxide electrodes probed by in situ electrochemical SHINERS. Chem. Commun. 2020, 56, 1129-1132.

[4] Moriau, L., Nazrulla, M.A., Logar, A., Pavko, L., Bele, M., Hodnik, N., Surca, A.K. Ir metal nanoparticles and IrO2 for acidic oxygen evolution reaction: Insight from Raman spectroscopy. Sust. Mater. Technol. 2024, 40, e00901.