Electrochemically Modifying the Electronic Structure of IrO₂ Nanoparticles for Overall Electrochemical Water Splitting with Extensive Adaptability

Abstract Designing the electrocatalysts that are stable and active for extensively adaptable water splitting is highly desirable for developing hydrogen based energy. IrO 2 is a promising and widely used catalyst for the oxygen evolution reaction in commercial applications, but is rarely used for the hydrogen evolution reaction (HER), due to the high Gibbs free energy for hydrogen adsorption (Δ G H* ). Herein, an approach to modify the electronic structure of IrO 2 via cyclic voltammetry is proposed. In this process, Ir(+4) is partially reduced and trace Pt is simultaneously deposited on IrO 2 , which greatly lowers the Δ G H* and thus accelerates the reaction kinetics. The as‐prepared Pt–IrO 2 /CC with low noble metal loading (36.6 µg cm −2 (Ir+Pt) ) exhibits excellent HER activity with overpotentials of 5, 22, and 26 mV at 10 mA cm −2 in 0.5 m H 2 SO 4 , 1 m KOH, and 1 m phosphate buffer solution, respectively, making it possible to organize an all‐IrO 2 based water electrolyzer. The Pt–IrO 2 /CC||IrO 2 /CC couple exhibits a promising activity and stability in pH‐universal conditions as well as natural seawater for H 2 production. Density function theory calculations reveal that the optimized electronic structure of IrO 2 balances the Δ G H* , resulting in a much enhanced HER performance.