In-situ monitoring of plasmon-induced nanoscale photocatalytic activity from Au-decorated TiO2 microflowers

Noble-metal-decorated semiconductor photocatalysts have attracted noticeable attention due to their enhanced photocatalytic activity. Herein, we have synthesized the pure rutile phase of TiO2 nanorods, with microflower morphology, using a hydrothermal method and decorated them with Au to observe plasmon-induced enhanced photocatalytic efficiency. The optical bandgap engineering through Au-decorated TiO2 introduces midgap states that help with charge compensation during photodegradation studies. The surface plasmonic resonance peak of Au is observed together with the defect peak of TiO2, extending the absorption of the solar spectrum from the UV to the visible region. The quenching in photoluminescence intensity with increased Au thickness indicates the formation of a Schottky junction at the interface of Au and TiO2 that helps to reduce photogenerated charge carrier recombination. The softening of the E- g Raman mode and photothermal effects originate from the nonradiative decay of localized surface plasmons through electron-phonon and phonon-phonon relaxation. The photocatalytic degradation of Rhodamine 6G is monitored by exposing the sample to UV and visible light sources under Raman spectroscopy. The Au decoration plays a crucial role in promoting charge separation, Schottky junction creation, photothermal effects, and UV to visible light absorption to enhance photocatalytic activity, which can be explained on the basis of the charge transfer mechanism. Our in-situ photodegradation study at the interface of noble metal and semiconducting materials will pave the way toward improving the understanding of plasmon-enhanced photocatalytic applications.