Influence of the photodeposition sequence on the photocatalytic activity of plasmonic Ag–Au/TiO2 nanocomposites

Abstract

Bimetallic Ag–Au/TiO₂ nanocomposites were synthesized by sequential photodeposition 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 for monometallic Ag/TiO₂ and Au/TiO₂ nanocomposites to yield maximum SPR absorption in the visible range. It was found that the photocatalytic activity of bimetallic Ag–Au/TiO₂ nanocomposites outperformed monometallic nanocomposites only when Au was photodeposited first on TiO₂, which was 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 galvanic replacement reaction during the second photodeposition. Alloying was not beneficial to the photocatalytic activity. These results demonstrate alloying during sequential photodeposition providing new insights for the synthesis of TiO₂-based photocatalysts with plasmon-enhanced absorption in the visible range.