Monoclinic SrIrO₃: An Easily Synthesized Conductive Perovskite Oxide with Outstanding Performance for Overall Water Splitting in Alkaline Solution

Fabricating efficient bifunctional catalysts for both hydrogen/oxygen evolution reactions (HER/OER) in an easy and mass-productive way is highly attractive for alkaline water electrolyzers. Perovskite oxides show compositional flexibility and high property tunability, while poor electrical conductivity and relatively low HER activity hamper their application in overall water splitting. Here, a conductive monoclinic SrIrO₃ perovskite is developed as an excellent alkaline electrocatalyst with bifunctionality which can be easily synthesized under normal conditions. Toward the HER, it experiences progressive surface self-reconstruction during the activation process because of lattice Sr²⁺ leaching, eventually leading to a remarkable apparent activity with an approximately 11-fold enhancement at 200 mV overpotential relative to the fresh sample. Experimental and theoretical evidence reveals that etching of lattice Sr²⁺ in relatively less-stable SrIrO₃ compared to IrO₂ is crucial for triggering this self-reconstruction. Toward the OER, no obvious surface reconstruction occurs, and an overpotential of only 300 mV is required to realize 10 mA cm_geo^–2, significantly lower than that for most perovskites reported previously (340–450 mV). The activated SrIrO₃ from HER operation can be used alternatively as an OER electrocatalyst with further improved performance. A SrIrO₃-based two-electrode water-splitting cell shows exceptional performance, that is, 1.59 V@10 mA cm_geo^–2 with negligible performance degradation over 10 h.