Customized Electronic Modulations of Transition Metal Chalcogenide Electrodes Via Heterointerfacing/High‐Valence Doping Toward High‐Performance Water Electrolysis with Ampere‐Level Current Density

Abstract Electrochemical water splitting offers an advancing approach to producing highly pure hydrogen and oxygen, motivated by the prevalence of a low‐carbon economy and the goal of a sustainable future. The customized modulation of electronic structures enables the electrocatalyst to directionally promote hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), which is a promising shortcut to overall water splitting (OWS). Herein, 3D homologous WSeS/CoSeS heterojunction nanoarrays (WSeS/CoSeS NAs) and W‐doped CoSeS nanoarrays (W‐CoSeS NAs) are investigated. Abundant heterointerfaces within WSeS/CoSeS NAs facilitate HER kinetics, boosting mass diffusivity, and increasing carrier separation and transfer process. High‐valence W⁶⁺ doping into CoSeS prevents phase separation and stabilizes Co sites by charge offset effect, leading to enhanced OER. Consequently, the WSeS/CoSeS NAs and W‐CoSeS NAs reach 10 mA cm⁻² at an overpotential of 43.8 and 233.3 mV in 1.0 m KOH electrolyte for HER and OER, respectively. Moreover, when asymmetrically engaged as an electrolyzer, this configuration exhibits extraordinary electrocatalytic performances (cell voltage of 1.51 V at 10 mA cm⁻²) with satisfying stability and mechanical robustness (over 1000 h at 1000 mA cm⁻²). The modulation and manufacture of reaction‐property‐oriented materials are experimentally and theoretically validated potential, illuminating the light of inspiration for multiple applications.