W⁵⁺–W⁵⁺ Pair Induced LSPR of W₁₈O₄₉ to Sensitize ZnIn₂S₄ for Full-Spectrum Solar-Light-Driven Photocatalytic Hydrogen Evolution

The localized surface plasmon resonances (LSPR) effect makes W₁₈O₄₉ an effective visible and near-infrared (NIR) light antenna to realize full-spectrum solar-light driven photocatalysis, yet the precise origin remains elusive. Here, the LSPR originates from the localized electron confinement around lattice W⁵⁺–W⁵⁺ pairs in the unique structure of W₁₈O₄₉ by density-functional theory calculation, which gives W₁₈O₄₉ a broad absorption ranging from visible to NIR region, independent of the particle shape and size is confirmed. This unique periodic LSPR simplifies the design of W₁₈O₄₉-sensitized photocatalytic composite into enhancing the light absorbance of W₁₈O₄₉ and screening photocatalytic semiconductors with suitable energy band potentials. To this end, hierarchical-structure W₁₈O₄₉ microflowers with high absorbance have been coated with ZnIn₂S₄ nanosheets to achieve cocatalyst-free photocatalytic composite, which presents an outstanding H₂ production rate of 902.57 µmol within 3 h under simulated solar-light. Comprehensive characterizations, including ultrafast transient absorption spectroscopy, prove the injection of hot electrons from W₁₈O₄₉ to ZnIn₂S₄ and the increase of long-lived active electrons. This work clarifies the LSPR origin of oxygen-deficient semiconductors and paves the way for the search of broad-spectrum active photocatalyst.