Gold nanoparticles immobilized on crystalline titanate fibres and shuttling effect of charges in solar photocatalysis

This study focuses on understanding the intriguing nature of charge transfer processes between immobilized gold nanoparticles (AuNPs) and bi-crystalline titanate nanofiber substrates in solar light photocatalysis. Colloidal AuNPs with an average diameter of 20 nm were stably immobilized on titanate bi-crystals via casein-derived peptide linkers. The peptide linking method was adopted in order to attach the same amount of AuNPs onto two different bi-crystalline titanate fibres, i.e., H-titanate fibres with anatase patches (Ti^H-A) and TiO₂-B fibres with anatase patches (Ti^B-A). The peptide cap surrounding the AuNPs was removed by combustion at 200 °C, leaving the AuNPs firmly bound to the titanate fibres. A pronounced charge transfer effect was observed in the photocatalysis investigation of the two types of bi-crystalline fibres. Facile shuttling of photoexcited charges between the anatase sheathed TiO₂-B fibres and AuNPs contributed significantly to the solar photocatalytic performance. In contrast, anatase sheathed H-titanate fibres were ineffective for enhancing the photoactivity after immobilization of gold particles. H-titante and TiO₂-B phases are known to be photocatalytically inactive under visible irradiation; however, alignment of the conduction band of TiO₂-B with anatase in the decorated fibres facilitated shuttling of charges by precluding fast recombination of electrons and holes. When the TiO₂-B phase was present in the bi-crystals, solar driven photocatalysis was enhanced, as evidenced by phenol degradation and photocurrent measurements.