Single-Phase Perovskite SrIrO₃ Nanofibers as a Highly Efficient Electrocatalyst for a pH-Universal Oxygen Evolution Reaction

pH-universal electrocatalysts are desirable for high efficiency of water electrolysis. Herein, we report the facile synthesis of single-phase perovskite SrIrO₃ nanofibers (NFs) and demonstrate that SrIrO₃ NFs are promising electrocatalysts for the oxygen evolution reaction (OER) in a wide range of pH. Single-phase SrIrO₃ NFs were synthesized by electrospinning and subsequent calcination processes, and the electrocatalytic performance of SrIrO₃ NFs toward the OER was evaluated under acidic, neutral, and alkaline media. A large surface area due to the NF morphology with an average diameter of 105.5 (± 15.5) nm led to enhanced catalytic activity of SrIrO₃ NFs, representing smaller overpotentials and Tafel slopes under pH-universal conditions than IrO₂/Ir NFs and commercial Ir/C. SrIrO₃ NFs also manifested remarkably stable activity for continuous OER operation in all three electrolytes, even though a considerable amount of Sr was leached out of them. The long-lasting high OER activity of SrIrO₃ NFs could be ascribed to stable Ir cations taking B sites of the perovskite oxide structure, known as an active site for electrocatalysis. The initial perovskite crystal structure of SrIrO₃ was maintained for a certain time even after significant Sr leaching. This work is the first application of SrIrO₃ perovskite for pH-universal OER catalysis.