Activation of Water-Splitting Photocatalysts by Loading with Ultrafine Rh-Cr Mixed-Oxide Cocatalyst Nanoparticles.

The activity of many water-splitting photocatalysts could be improved by the use of Rh-III-Cr-III mixed oxide (Rh2-xCrxO3) particles as cocatalysts. Although further improvement of water-splitting activity could be achieved if the size of the Rh2-xCrxO3 particles was decreased further, it is difficult to load ultrafine (<2 nm) Rh2-xCrxO3 particles onto a photocatalyst by using conventional loading methods. In this study, a new loading method was successfully established and was used to load Rh2-xCrxO3 particles with a size of approximately 1.3 nm and a narrow size distribution onto a BaLa4Ti4O15 photocatalyst. The obtained photocatalyst exhibited an apparent quantum yield of 16 %, which is the highest achieved for BaLa4Ti4O15 to date. Thus, the developed loading technique of Rh2-xCrxO3 particles is extremely effective at improving the activity of the water-splitting photocatalyst BaLa4Ti4O15. This method is expected to be extended to other advanced water-splitting photocatalysts to achieve higher quantum yields.