W${}^{5+}$-W${}^{5+}$ pair induced LSPR of W${}_{18}$O${}_{49}$ to sensitize ZnIn${}_2$S${}_4$ for full-spectrum solar-light-driven photocatalytic hydrogen evolution

The localized surface plasmon resonances (LSPR) effect makes W${}_{18}$O${}_{49}$ 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 W${}^{5+}$-W${}^{5+}$ pairs in the unique structure of W${}_{18}$O${}_{49}$ by density-functional theory calculation, which gives W${}_{18}$O${}_{49}$ 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 W${}_{18}$O${}_{49}$-sensitized photocatalytic composite into enhancing the light absorbance of W${}_{18}$O${}_{49}$ and screening photocatalytic semiconductors with suitable energy band potentials. To this end, hierarchical-structure W${}_{18}$O${}_{49}$ microflowers with high absorbance have been coated with ZnIn${}_2$S${}_4$ nanosheets to achieve cocatalyst-free photocatalytic composite, which presents an outstanding H${}_2$ 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 W${}_{18}$O${}_{49}$ to ZnIn${}_2$S${}_4$ 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. (© 2022 Wiley‐VCH GmbH)