Symmetric Catalyst Design Employing Ir Nanoparticles on Black WO_3‐x Nanofiber Support for Boosting Water Electrolysis

Abstract The efficient evolution of gaseous hydrogen and oxygen from water is required to realize sustainable energy conversion systems. To address the sluggish kinetics of the multielectron transfer reaction, bifunctional catalyst materials for both the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) should be developed. Herein, a tailored combination of atomically minimized iridium catalysts and highly conductive black WO_3‐x nanofiber supports are developed for the bifunctional electrolyzer system. Atomic Ir catalysts, particularly those that activate the OER, minimize the utilization of precious metals. The oxygen‐deficient black WO_3‐x NF support, which boosts the HER, offers increased electronic conductivity and favorable nucleation sites for Ir loading. The Ir‐black WO_3‐x NFs exhibit increased double‐layer capacitance, a significantly reduced onset potential, lower Tafel slope, and stable cyclability for both the OER and HER, compared to large‐sized Ir catalysts loaded on white WO₃ nanofibers. This study offers a strategy for developing an optimal catalyst material with suitable supports for high‐performance and economical water electrolysis systems for achieving carbon‐negative targets.