Single Molecular Catalysis Identifying Activation Energy of Intermediate Product and Rate-Limiting Step in Plasmonic Photocatalysis

Plasmon mediated photocatalysis provides a novel strategy for harvesting solar energy. Identification of rate determining step and its activation energy in plasmon mediated photocatalysis plays critical roles for understanding the contribution of hot carriers that facilitates rational designing catalysts with integrated high photo-chemical conversion efficiency and catalytic performance. However, it remains a challenge due to a lack of research tools with spatiotemporal resolution that capable of capturing intermediates. In this work, we used a single molecular fluorescence approach to investigate a localized surface plasmon resonance (LSPR) enhanced photocatalytic reaction with sub-turnover resolution. By introducing variable temperature as an independent parameter in plasmonic photocatalysis, the activation energies of tandem reaction steps, including intermediate generation, product generation and product dissociation, were clearly differentiated, and intermediates generation was found to be the rate-limiting step. Remarkably, the cause of plasmon enhanced catalysis performance was found to be its ability of lowering the activation energy of intermediates generation. This study gives new insight into the photo-chemical energy conversion pathways in plasmon enhanced photocatalysis and sheds light on designing high performance plasmonic catalysts.