Influence of the Au particle size on the catalytic performance of plasmonic Au/TiO2 nanocatalysts in the sunlight-powered reverse water gas shift reaction

Abstract

Plasmon catalysis for endothermic reverse water-gas shift (rWGS) reaction making use of sunlight and renewable hydrogen is a low temperature alternative to the conventional thermal process. 1 A plasmonic catalyst consists of plasmonic nanoparticles dispersed on a supporting oxide, which can be semiconducting or insulating. The plasmonic nanoparticles exhibits localised surface plasmon resonance (LSPR) upon illumination. This results in the catalyst exhibiting following pathways to catalyse reactions: 2-Local heat generation (fig. A)-Near field enhancement (fig. B)-Hot electron injection (fig. C)-Charge separation over Schottky barrier (if semiconducting support) (fig. D)-Band gap activity of semiconductor (if semiconducting support) (Fig. E) To investigate which catalytic effects contribute to rWGS reaction: Au was chosen as plasmonic nanoparticle for a high selectivity towards CO production and strong plasmonic resonance. P25 TiO 2 was chosen as semiconducting oxide with a band gap in the near UV and good photocatalytic properties. In order to investigate the catalytic effects at play, as well as the impact of plasmonic nanoparticle size, smaller (5.5 nm) and larger (16 nm) particles were synthesised on the TiO 2 support and tested for catalytic activity in both light and dark conditions.