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

Designing the electrocatalysts that are stable and active for extensively adaptable water splitting is highly desirable for developing hydrogen based energy. IrO2 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 (ΔGH*). Herein, an approach to modify the electronic structure of IrO2 via cyclic voltammetry is proposed. In this process, Ir(+4) is partially reduced and trace Pt is simultaneously deposited on IrO2, which greatly lowers the ΔGH* and thus accelerates the reaction kinetics. The as‐prepared Pt–IrO2/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 H2SO4, 1 m KOH, and 1 m phosphate buffer solution, respectively, making it possible to organize an all‐IrO2 based water electrolyzer. The Pt–IrO2/CC||IrO2/CC couple exhibits a promising activity and stability in pH‐universal conditions as well as natural seawater for H2 production. Density function theory calculations reveal that the optimized electronic structure of IrO2 balances the ΔGH*, resulting in a much enhanced HER performance. Benefiting from the optimization of the electronic structure and the ultrafine size, the as‐prepared PtIrO2/CC||IrO2/CC electrode exhibits an attractive performance for overall electrochemical water splitting in pH‐universal conditions and even seawater (without any treatment).