Direct conversion of solar to chemical energy has gained renewed interest in the recent years. Plants uptake atmospheric CO2 to produce sugar by the process of photosynthesis. Recreating this process requires materials which can absorb light and convert it into energy. Plasmonic nanoparticles of silver and gold are excellent candidates for photocatalysis due to their high absorption cross section. In my talk, I will show that under light irradiation, silver nanoparticles catalyze CO2 reduction reaction. Spatially resolved single particle surface enhanced Raman spectroscopy shows formation of intermediate such as HOCO* as well products such as carbon monoxide and formic acid. Further, binding geometry of HOCO* plays decisive role in directing the reaction either towards carbon monoxide or formic acid.
Although catalytic reaction on plasmonic nanostructures is fairly well studied, the fate of metal nanoparticles post photocatalysis is largely unknown. We found that plasmon-assisted CO2 reduction reaction induces significant directional restructuring on catalyst surface. In the second part of the talk, I will show you how these structural changes in plasmonic catalysts also gives an insight into the mechanism of photocatalytic activation, the distribution of active sites on nanoparticle surface and the definite role of light.