In Situ Growth of 3D N-IrNiCoO Nanocomposite with Ultralow Ir Loading as Efficient Bifunctional Electrocatalyst for Overall Water Splitting

Reasonably developing and designing bifunctional electrocatalysts with high activity is crucial for continuously obtaining hydrogen fuel during the overall water-splitting process. Earth-abundant spinel nickel cobaltite materials have been investigated as promising oxygen evolution reaction (OER) catalysts in alkaline solution. However, its insufficient performance in the hydrogen evolution reaction (HER) significantly restricts its applicability in integrated water-splitting systems. In this study, a cationic doping and plasma nitriding strategy is employed to synthesize Ir- and N-codoped nickel cobaltite (N-IrNiCoO/CC) as a highly efficient bifunctional electrocatalyst. The incorporation of Ir and N dopants effectively modifies the electronic structure, introduces abundant oxygen vacancies, and enhances the electrical conductivity, thereby substantially improving the catalytic activity. Consequently, the optimized N-IrNiCoO/CC electrode exhibits outstanding bifunctional performance, requiring low overpotentials of 46 mV for HER and 203 mV for OER at a current density of 10 mA cm^-2. Assembled in a two-electrode configuration, the N-IrNiCoO/CC||N-IrNiCoO/CC electrolyzer delivers a low cell voltage of 1.46 V at 10 mA cm^-2, outperforming commercial Pt/C||Ir/C (1.67 V). Moreover, the electrolyzer retains over 97% of its initial activity after 50 h of operation at 50 mA cm^-2, despite a low Ir loading of only 1.36 wt %. These results highlight the strong potential of N-IrNiCoO/CC as a cost-effective and high-performance electrocatalyst for sustainable hydrogen production.