Plasmon-enhanced photocatalytic overall water-splitting over Au nanoparticle-decorated CaNb2O6 electrospun nanofibers

The design and construction of wide-bandgap semiconductor nanostructures is a promising way to achieve photocatalytic overall water-splitting, because their redox potentials easily simultaneously satisfy the thermodynamic requirements of water reduction and oxidation. However, the narrow light-harvesting range and the fast charge recombination of wide-bandgap semiconductors tremendously limit their photocatalytic activities. Herein, we developed a novel wide-bandgap semiconductor photocatalyst of CaNb2O6 nanofibers (NFs) fabricated by an electrospinning technique, followed by calcination. Upon UV-visible light irradiation, the as-electrospun CaNb2O6 NFs could split water into H-2 and O-2 without adding any cocatalyst and sacrificial agent. The H-2-production rate of CaNb2O6 NFs was similar to 7.7 times higher than that of CaNb2O6 nanoparticles (NPs). It is because the CaNb2O6 NFs with the NP-packed 1D nanostructure possess abundant homogeneous interfaces to facilitate inter-particle continuous charge migration, thereby prolonging the lifetimes of photoinduced electrons and holes toward both water reduction and oxidation. Notably, the introduction of Au NPs into the CaNb2O6 NFs could extend light absorption from the UV to the visible light range. The optimal sample of 1.0 at% Au NP-decorated CaNb2O6 NFs exhibited similar to 13.1-fold enhancement of photocatalytic activity for overall water splitting as compared to CaNb2O6 NFs. This remarkable enhancement is attributed to an interesting plasmonic sensitization process, during which the visible-light-excited hot electrons in plasmonic Au NPs are able to transfer to the interband-excited CaNb2O6 across their hetero-interface for enhancing the photocatalytic water reduction. Meanwhile, the hot holes left in the Au NPs possess a longer lifetime for fulfilling the photocatalytic water oxidation.