Plasmon photocatalytic CO 2 reduction reactions over Au particles on various substrates.

Surface plasmonic effects have been widely used in photocatalytic reactions like CO 2 conversion in the past decades. However, owing to the significant controversy in the physical processes of plasmon photocatalytic reactions and difficulty in realizing CO 2 reduction, the influence mechanism of the plasmon effect on the CO 2 photoreduction is still under debate. In this study, Au particles deposited on various substrates were employed to acquire insights into the plasmon photocatalytic CO 2 reduction, including SiO 2 , n-Si, p-Si, TiO 2 -SiO 2 , TiO 2 -n-Si, and TiO 2 -p-Si. It was found that the plasmon resonant enhancement (PRE) effect of Au-SiO 2 caused by the Au plasmon was stronger than that of Au-TiO 2 -SiO 2 and Au-n-Si (Au-p-Si) in the visible-light range, while it was weaker for Au-n-Si (Au-p-Si) samples than Au-TiO 2 -n-Si (Au-TiO 2 -p-Si). The simulation results agree with the experimental conclusions. The photocatalytic results indicated that the catalytic activity of Au-n-Si (Au-p-Si) samples was lower than that of Au-TiO 2 -n-Si (Au-TiO 2 -p-Si), and Au-SiO 2 was lower than Au-TiO 2 -SiO 2 and Au-n-Si (Au-p-Si) samples, suggesting that the direct electron transfer (DET) mechanism was dominant here compared with the PRE mechanism.