Robust Alkaline Hydrogen Evolution From Ru‐degenerate Doped WS ₂ /WSe ₂ <i>p‐n</i> Junction Heterostructure Electrocatalyst

ABSTRACT Heterostructure engineering has emerged as a promising strategy for the development of highly efficient electrocatalysts for water splitting applications among numerous design principles for novel catalysts. The strong built‐in potential, large surface‐active sites, and interfacial electronic structure coupling promote the charge transfer process of the heterostructures, making them ideal catalysts for electrochemical energy generation. Nonetheless, the hydrogen evolution reaction (HER) performance of the van der Waals heterostructure catalysts significantly lags behind that of commercial Pt group catalysts, especially under alkaline conditions. Herein, we successfully developed a Ru‐degenerate doped WS 2 /WSe 2 (Ru‐WS 2 /WSe 2 ) p‐n junction heterostructure catalyst, demonstrating its exceptional HER activity and good stability in an alkaline medium. The WS 2 /WSe 2 and Ru‐WS 2 /WSe 2 heterostructures, with ideal factors of 1.8 and 1.7, display rectification behavior, indicating the formation of a p‐n junction diode. The Ru‐WS 2 /WSe 2 p‐n junction heterostructure catalyst delivers a 10 mA cm − 2 current density at a remarkable overpotential of 47 mV vs. RHE with a low Tafel slope of 25 mV dec − 1 , outperforming the standard Pt/C catalyst in 1 m KOH electrolyte. Further, the same electrode required 1.43 V to deliver a 10 mA cm −2 current density in a symmetric full cell water electrolyzer. This work opens the pathway for the development of 2D materials‐based low‐cost and highly efficient heterostructure catalysts for electrochemical energy generation.