An N-defective graphitic carbon nitride-supported Ir/Fe catalyst with low Ir-content as highly efficient oxygen evolution reaction catalyst for acidic water splitting

To develop a low-cost acidic water electrolysis catalyst with high efficiency and stability and low Ir content, a catalyst with highly dispersed Ir/Fe complex sites (∼ 5 wt% Ir) was synthesized by a simple carbonization and oxidation process. N-defective g-C3N4 (NCN) was introduced to enhance the support effect between metal nanoparticles and CN bases and the intrinsic catalytic activity for the oxygen evolution reaction (OER). NCN provided more active sites and adjusted the electronic structure of CN. Compared with the original single Ir catalyst, the electrons of the Ir-Fe metal catalyst were transferred from the base to the metal, which maintained the high OER performance and stability of the catalyst. Density functional theory calculations demonstrated that the Gibbs free energy of Ir/Fe@NCN was greatly reduced during O*→OOH* as the rate-determining step. The overpotential of the Ir/Fe@NCN catalyst was 242 mV at 10 mA/cm2, and its mass activity (612.6 A/g) was much higher than that of IrO2 (88.6 A/g), showing excellent OER performance. This study provides a new strategy for the design and optimization of highly efficient and low-cost acidic Ir/transition metal OER catalysts.