Tetra-Coordinated W₂ S₃ for Efficient Dual-pH Hydrogen Production

Two-dimensional (2D) transition-metal dichalcogenides (TMDs) have emerged as promising catalysts for the hydrogen evolution reaction (HER) that play a crucial role in renewable energy technologies. Breaking the inherent structural paradigm limitations of 2D TMDs is the key to exploring their fascinating physical and chemical properties, which is expected to develop a revolutionary HER catalyst. Herein, we unambiguously present metallic W₂ S₃ instead of energetically favorable WS₂ via a unique stoichiometric growth strategy. Benefiting from the excellent conductivity and hydrophilicity of the tetra-coordinated structure, as well as an appropriate Gibbs free energy value and an enough low energy barrier for water dissociation, the W₂ S₃ as catalyst achieves Pt-like HER activity and high long-term stability in both acidic and alkaline electrolytes. For application in proton exchange membrane (PEM) and anion exchange membrane (AEM) electrolysers, W₂ S₃ as the cathode catalyst yields excellent bifunctionality index (ɳ $$ =1.73 V, ɳ $$ =1.77 V) and long-term stability (471 h@PEM with a decay rate of 85.7 μV h^-1 , 360 h@AEM with a decay rate of 27.1 μV h^-1 ). Our work provides significant insight into the tetra-coordinated W₂ S₃ and facilitates the development of advanced electrocatalysts for sustainable hydrogen production.