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

Abstract

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 H₂ and O₂ without adding any cocatalyst and sacrificial agent. The H₂-production rate of CaNb₂O₆ NFs was ∼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 ∼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.