In Situ Synthesis of Mesoporous TiO₂ Nanofibers Surface-Decorated with AuAg Alloy Nanoparticles Anchored by Heterojunction Exhibiting Enhanced Solar Active Photocatalysis

We designed an electrospinning synthesis protocol to obtain in situ, the mesoporous TiO₂ nanofibers, which are surface-decorated with plasmonic AuAg nanoparticles (AuAg-mTNF-H). Such alloy nanoparticles are found to be partially exposed on the surface of the nanofibers. Characterization by HRTEM and EDS confirmed the formation of 1:1 AuAg alloy nanoparticles on the surface of TiO₂ nanofibers with heterojunction at the interfaces. On the basis of electron microscopic characterization, we proposed that, during the formation of the nanofibers, the incorporated metal ions with surface capping of negative charges migrated toward the outer surface of the nascent fibers under the influence of high positive voltage required for electrospinning. As a result, after the subsequent thermal treatment, the crystallization of TiO₂ nanofibers and the formation of alloy nanoparticles took place, leading to the formation of a deep heterojunction through partial embedment of the nanoparticles. The formation of AuAg alloy also restricted the oxidation of Ag, thus making the nanoparticles highly stable in ambient condition. Accordingly, such unique AuAg-mTNF-H photocatalyst shows strong light absorption property covering the entire range of visible wavelengths with stability. The solar light harvesting property of AuAg-mTNF-H was verified by monitoring solar light induced H₂ evolution via water splitting and photodecomposition of MB. In both the cases AuAg-mTNF-H showed excellent H₂ evolution and photodecomposition of dye.