Photogenerated charge carrier dynamics on Pt-loaded SrTiO3 nanoparticles studied via transient-absorption spectroscopy

Abstract

Loading cocatalysts on semiconductor-based photocatalysts to create active reaction sites is a preferable method to enhance photocatalytic activity and a widely adopted strategy to achieve effective photocatalytic applications. Although theoretical calculations suggest that the broad density of states of noble metal cocatalysts, such as Pt, act as a recombination center, this has never been experimentally demonstrated. Herein, we employed pico–nano and nano–micro second transient absorption spectroscopy to investigate the often overlooked photogenerated holes, instead of the widely studied electrons on Pt- and Ni-loaded SrTiO₃ to evaluate the effects of cocatalysts as a recombination center. It is demonstrated that Pt serves as the recombination center with no sacrificial agent; recombination can be suppressed by a hole scavenger, while recombination is not significant on Ni with localized density of states. It is also found that photo-generated holes in SrTiO₃ tend to migrate to Pt within 400 ps, and photo-generated holes generated in the bulk gradually migrate to Pt cocatalysts in a micro-second regime.