Synthesis of plasmonic W18O49 interconnected nanowire frameworks with strong photo-enhanced hydrogen evolution reaction activity

Abstract

The synthesis of high-order tungsten oxide nanowire frameworks (NWFs) is achieved using an unordinary stable molecular precursor formed by mixing tungsten hexachloride with methanol. The solvothermally obtained NWFs are well characterized with diffraction, microscopy, and nitrogen adsorption techniques. Time-resolved absorption spectroscopy and proton activity measurements reveal the stability of tungsten precursors in methanol. In butanol, the precursor decomposes rapidly into solid hydrated tungsten oxide and leads to the formation of freestanding nanowires (FNWs) after the solvothermal treatment. The NWFs show a blue shift in their characteristic plasmonic absorption wavelength when compared with FNWs. Such phenomenon is attributed to the high population of connecting nodes, which are postulated to be the plasmonic hot spots where the light-induced electromagnetic fields are amplified. The photo-deposition of palladium nanoparticles was hence selectively formed on these connecting nodes on the NWFs while showing no apparent selectivity on the FNWs. Furthermore, when applied as an electrode catalyst for the hydrogen evolution reaction, the NWFs demonstrated a much stronger photo-induced enhancement compared with the FNWs. The photo-induced effects demonstrate the advantage of plasmonic field enhancement through connected nanowires which can be obtained through a facile synthesis process.