The Effects of Co-catalyst on Water-splitting Photocatalyst: A DFT Analysis*

Water splitting photocatalysts are getting a lot of attention due to their ability to produce H₂ by utilizing solar energy. One of the promising way to boost their efficiency is to load co-catalysts such as noble metal nanoparticles on the photocatalysts. Co-catalysts are believed to separate photogenerated electrons and holes by forming a Schottky barrier at the metal-semiconductor interface, at which O₂ and H₂ evolution reaction (OER, HER) are thought to occur. Nevertheless, the details of the reactive sites and the reaction mechanism are still not clear due to the difficulty in detecting OER and HER experimentally.
Thus, in our research, we aimed to elucidate the role of co-catalysts in HER by means of first-principle calculations. We used Pt/SrTiO₃ as an example, and found the stable structure of dissociative adsorption of H₂O. The calculations suggested that H⁺ moves onto co-catalysts while OH^- stays on the surface around co-catalysts. We also revealed that co-catalysts donate electrons to their adsorbents. We will also investigate the changes of the charge distribution of transition states during the water splitting reaction on the surface.