Electrochemical Evolution of Ru‐Based Polyoxometalates into Si,W‐Codoped RuO_x for Acidic Overall Water Splitting

Abstract Despite intensive studies over decades, the development of electrocatalysts for acidic water splitting still relies on platinum group metals, especially Pt and Ir, which are scarce, expensive, and poorly sustainable. Because such problems can be alleviated, Ru‐based bifunctional catalysts such as rutile RuO₂ have recently emerged. However, RuO₂ has a relatively low activity for hydrogen evolution reactions (HER) and low stability for oxygen evolution reactions (OER) under acidic conditions. In this study, the synthesis of a RuO_x‐based bifunctional catalyst (RuSiW) for acidic water splitting via the electrochemical evolution from Ru‐based polyoxometalates at cathodic potentials is reported. RuSiW consists of the nanocrystalline RuO₂ core and Si,W‐codoped RuO_x shell. RuSiW exhibits outstanding HER and OER activity comparable to Pt/C and RuO₂, respectively, with high stability. Computational analysis suggests that the codoping of RuO_x with W and Si synergistically improves the HER activity of otherwise poor RuO₂ by shifting the d‐band center and optimizing atomic configurations beneficial for proper hydrogen adsorption. This study provides insights into the design and synthesis of unprecedented bifunctional electrocatalysts using catalytically inactive and less explored elements, such as Si and W.