IrO₂-ZnO Composite Nanorod Array as an Acid-Stable Electrocatalyst with Superior Activity for the Oxygen Evolution Reaction

An IrO₂-ZnO composite nanorod array with distinct morphological features was successfully fabricated through a facile method via a simple acid-base reaction, followed by a postcalcination process. A modulation in the annealing treatment time (t) generated the variation in morphology, at a constant temperature (600 °C), and the nanorod-like growth on the surfaces was revealed at t ≥ 3 h. Especially, the IrO₂-ZnO composite nanorod array exhibited superior OER catalytic activities (e.g., a potential of 1.481 V at 10 mA cm^-2(vs RHE) and a Tafel slope of 42.9 mV dec^-1). Moreover, there was no apparent potential shift with robust long-term cycling stability under acidic conditions, which were much better than those of IrO₂and commercial iridium (cIr) and comparable with those of the previously reported outstanding Ir-based OER catalysts. Considering that the nanorod array was fabricated with the loading of the Zn metal component, which showed generally low catalytic activity and poor durability, this study suggests a promising strategy with an extended synthetic methodology for preparing Zn-mixed metal oxides as highly efficient electrocatalysts.