Influence of the photodeposition sequence on the photocatalytic activity of plasmonic Ag-Au/TiO 2 nanocomposites.

Bimetallic Ag-Au/TiO 2 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/TiO 2 and Au/TiO 2 nanocomposites to yield maximum SPR absorption in the visible range. It was found that the photocatalytic activity of bimetallic Ag-Au/TiO 2 nanocomposites outperformed monometallic nanocomposites only when Au was photodeposited first on TiO 2 , 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 TiO 2 -based photocatalysts with plasmon-enhanced absorption in the visible range.