Plasmonic platinum nanoparticles-tungsten oxide nanoarchitectures as visible light photocatalysts for highly efficient overall water splitting

Visible plasmonic Pt nanoparticles (NPs) have rarely been used as a photosensitizer for the semiconductor photocatalysis of overall water splitting (OWS), while they show higher probabilities of electron-hole (e-h) pair excitations and Pt catalysts are highly active for both water reduction and oxidation in comparison with plasmonic Au and Ag. Herein, we fabricate a tungsten oxide (WO 3 ·0.5H 2 O-WO 3 ) superstructure decorated by a series of visible plasmonic Pt NPs with a uniform diameter (120, 130, 145, and 160 nm) on nickel foam (NF) substrate. These monolithic composite Pt-WO 3 ·0.5H 2 O-WO 3 photocatalysts are capable of efficiently harvesting visible light for more efficient solar-hydrogen conversion due to the narrow bandgap of WO 3 ·0.5H 2 O-WO 3 (2.4 eV) coupled with an extension of light absorption even up to above 800 nm contributed by Pt NPs. In particular, our Pt-WO 3 ·0.5H 2 O-WO 3 photocatalysts exhibit favorable band edge positions relative to water redox potentials and intrinsic Pt catalytic activity and thus achieve an exceptional activity towards photocatalytic OWS (POWS) with apparent quantum efficiencies (AQE) of more than 10% within the range of visible light and a solar-to-hydrogen (STH) conversion efficiency of 7.6%. The dependence of the photocatalytic activity of Pt-WO 3 ·0.5H 2 O-WO 3 on the diameter of Pt NPs is attributed to a trade-off between optical absorption range and probability for interband damping of localized surface plasmon resonance (LSPR) into e-h excitations. Plasmon-enhanced Pt-WO 3 ·0.5H 2 O-WO 3 photocatalysts were prepared for photocatalytic overall water splitting under visible light and simulated sunlight irradiation. Exceptional STH efficiency (7.6%) and AQEs of higher than 10% have been achieved.