Tunable Catalytic Performance on Iridium Clusters‐Interspersed Co_xS_y‐CoO Nanosheet‐Built Hollows for Enhanced Water Splitting

Abstract To reach sustainable and robust green hydrogen energy production, the development of effective and long‐lasting electrocatalysts for hydrogen and oxygen evolution reactions (HER and OER) during overall electrochemical water splitting is a critical requirement. In this study, a novel hierarchical nanosheet‐based hollow heterostructure of Co_xS_y‐CoO integrated with active iridium clusters (Ir_Cs‐Co_xS_y‐CoO) is prepared by a straightforward chemical synthesis approach. The heterostructure offers extensive tunnels, and abundant mesopores, and features a high‐density active site at the interfaces, thus greatly improving the overall catalytic performance through the promotion of synergistic effects. The Ir_Cs‐Co_xS_y‐CoO catalyst demonstrates low overpotentials of 97 mV for HER and 243 mV for OER at 10 mA cm⁻², showcasing remarkable stability and efficiency. The two‐electrode cell test demonstrates reliable current response of 10 mA cm⁻² at voltage of 1.497 and 1.58 V at temperature of 75 and 25 °C, respectively. Furthermore, the Ir_Cs‐Co_xS_y‐CoO catalyst exhibits enhanced durability and performance when compared to the Pt/C₍₋₎//RuO₂₍₊₎. In practical application, significant current of 0.5/1.0 A cm⁻² at 1.8/1.97 V has been achieved in an anion exchange membrane electrolyzer stack, while maintaining high efficiency (68%) and exceptional stability (over 500 h), underscoring the promising potential for sustainable H₂ energy production.