Customized structural reconstruction for an IrOx catalyst using Ni–Co dual coordination towards enhanced water electrolysis in PEM electrolyzers

Abstract

Efficient and robust electrocatalysts applicable to acid water electrolysis are crucial for the development of high-performance PEM (proton exchange membrane) electrolyzers. Herein, a customized structural reconstruction strategy is developed to tackle the activity-stability paradox of the IrO_x electrocatalyst for acid water electrolysis. By tuning the structural reconstruction of the NiCoIr alloy, a crystallized NiCo–IrO_x catalyst with a 3D nanoporous structure is obtained. At Ir loading as low as 0.62 mg cm⁻², the NiCo–IrO_x catalyst achieves a record low overpotential of 209 mV for oxygen evolution and 37 mV for hydrogen evolution to reach 10 mA cm⁻². Negligible degradation is observed for operating over 100 h at a current density of 100 mA cm⁻². The NiCo–IrO_x catalyst showcases superior performance and considerable potential in proton exchange membrane (PEM) electrolyzer application. In situ analysis combined with theoretical simulations reveals a distinct modulation mechanism of Ni and Co on the reconstruction of Ir sites. The deployment of Ni primarily augments the exposure of active sites, while Co doping modifies the electronic structure of Ir sites, optimizes the adsorption energy of reaction intermediates and suppresses the participation of lattice oxygen during the oxygen evolution reaction. The coordination of Ni and Co balances the geometric and electronic effects, thus enhancing the activity and stability of the IrO_x catalyst simultaneously.