Morphology Control of Energy-Gap-Engineered Nb2O5 Nanowires and the Regioselective Growth of CdS for Efficient Carrier Transfer Across an Oxide-Sulphide Nanointerface

Abstract

Semiconductor nanowires with both nano- and micrometre dimensions have been used as effective materials for artificial photosynthesis; however, a single synthesis approach to provide rational control over the macroscopic morphology, which can allow for the high-throughput screening of photocatalytic performance, and carrier transfer between oxide and sulphide nanostructures has been poorly known. Our recent findings indicate that a single parameter, Nb foil thickness, in a vapor-phase synthesis method can alter the macroscopic morphology of resulting Nb2O5 nanowires. Thick Nb foil results in a free-standing Nb2O5 film, whereas a thinner foil leads to fragmentation to give a powder. During the synthesis process, a Rh dopant was provided through metal-organic chemical vapor deposition to reduce the Nb2O5 energy gap. Upon irradiation with visible light (λ > 440 nm), the free-standing nanowire film [Nb2O5:Rh-NW(F)] showed photoanodic current with a Faradaic efficiency of 99% for O2 evolution. Under identical irradiation conditions, the powdered counterpart [Nb2O5:Rh-NW(P)] showed activity for O2 evolution in the presence of an electron acceptor. The poor water-reduction ability was greatly enhanced by the Au-catalysed vapor-liquid-solid (VLS) growth of H2-evolving CdS onto the reduction sites of Nb2O5:Rh-NW(P) [Au/CdS/Nb2O5:Rh-NW(P)].