Dual CoS-Modified Tungsten Disulfide Double-Heterojunction Electrocatalyst for Efficient Hydrogen Evolution in All-pH...

The rational design and preparation of a heterogeneous electrocatalyst for hydrogen evolution reaction (HER) has become a research hotspot, while applicable and pH-universal tungsten disulfide (WS₂)-based hybrid composites are rarely reported. Herein, we propose a novel hybrid catalyst (WS₂/Co₉S₈/Co₄S₃) comprising two heterojunctions of WS₂/Co₄S₃ and WS₂/Co₉S₈, which grow on the porous skeleton of Co, N-codoped carbon (Co/NC) flexibly applicable to all-pH electrolytes. The effect of double heterogeneous coupling on HER activity is explored as the highly flexible heterojunction is conducive to tune the activity of the catalyst, and the synergistic interaction of the double heterojunctions is maximized by adjusting the proportion of heterojunction components. Theoretical calculations show that both WS₂/Co₉S₈ and WS₂/Co₄S₃ heterojunctions have a Gibbs free energy of H reaction (|ΔG_H*|) close to 0.0 eV and a facile decomposition water barrier. As collective synergy of dual CoS-modified WS₂ double heterojunction, WS₂/Co₉S₈/Co₄S₃ greatly enhances HER activity compared to bare Co₉S₈/Co₄S₃ or single heterojunction (WS₂/Co₉S₈) in all-pH media. Besides, we have elucidated the unique HER mechanism of the double heterojunction to decompose H₂O and confirm its excellent activity under alkaline and neutral conditions. Thus, this work provides new insights into WS₂-based hybrid materials potentially applied to sustainable energy.