Tunable Catalytic Performance on Iridium Clusters-Interspersed CoxSy-CoO Nanosheet-Built Hollows for Enhanced Water Splitting

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.