Single Atoms in Photocatalysis: Low Loading Is Good Enough!
Shanshan Qin, Johannes Will, Hyesung Kim, Nikita Denisov, Simon Carl, Erdmann Spiecker, Patrik Schmuki
Abstract
We disperse Pt single atoms (SAs) with different loading densities on anatase TiO 2 thin films and evaluate the photocatalytic H 2 generation as a function of the incident light intensity. We show that under common illumination intensities (such as terrestrial solar illumination), a minuscule Pt SA loading of ∼10 5 atoms μm –2 (surface Pt content ∼0.1 at.%) is sufficient to achieve a maximized H 2 production rate. This results in a maximum turnover frequency at a single Pt atom site of ∼300 H 2 molecules s –1 . For a vast majority of illumination conditions and a suitable surface configuration, it is not the density of co-catalytic sites that is rate-determining (a high loading is not needed!), but the charge carrier generation (and flux of photoelectrons to the co-catalytic centers) determines the overall reaction rate. This is in stark contrast to SA catalysis of classic chemical reactions where generally a maximum loading of reactive SA delivers a maximum activity.