Tailored mesoporous Ir/TiOx: Identification of structure-activity relationships for an efficient oxygen evolution reaction

Abstract The depletion of fossil resources coupled with an increasing demand in both sustainable and renewable energy sources further strengthen the development of highly efficient electrocatalytic water splitting catalysts. Iridium oxide is well known for its excellent activity and stability during acidic oxygen evolution reaction (OER). However, high prices and rare abundance demand the most efficient utilization. We report a new synthesis approach for iridium/titanium-based mixed oxides with a tailored mesopore structure employing iridium acetate and titanium chloride as precursors. The new Ir/TiO x system outperforms OER catalysts based on other titanium precursors by a factor of up to two. The material is used as a model system to investigate the impact of synthesis and structural parameters on OER performance. We find that calcination temperature and iridium content are the main synthesis parameters to achieve tailored structures and superior electrochemical activity. The highest surface area and OER-activity are attained for samples with a fully developed mesoporous network and small crystallite sizes obtained by a moderate calcination around 400 °C. A minimum content of iridium is required to achieve sufficient electrical conductivity, whereas at higher iridium content the OER performance scales approximately linearly.