Influence of Photodeposition Sequence on the Photocatalytic Activity of Plasmonic Ag–Au/TiO₂ Nanocomposites

Abstract

Bimetallic Ag–Au/TiO2 nanocomposites were synthesized by sequentialphotodeposition in order to investigate the effect of surface plasmon resonance (SPR) properties on photocatalytic activity for solar water splitting and methylene blue (MB) degradation. The photodeposition times were optimized formonometallic Ag/TiO2 and Au/TiO2 nanocomposites to yield maximum SPR absorption in the visible range. It was found that the photocatalytic activity ofbimetallic Ag–Au/TiO2 nanocomposites outperformed monometallic nanocomposites only when Au was photodeposited first on TiO2, whichwas attributed to Au-core–Ag-shell nanoparticle morphology. In contrast, reversing the photodeposition order resulted in Ag–Au alloy nanoparticle morphology, which was mediated by the galvanicreplacement reaction during the second photodeposition. Alloying was not beneficial to thephotocatalytic activity. These results demonstrate alloying during sequential photodeposition providingnew insights for the synthesis of TiO2-based photocatalysts with plasmon-enhanced absorption in thevisible range.