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 (Rh_2-x Cr_x O₃ ) particles as cocatalysts. Although further improvement of water-splitting activity could be achieved if the size of the Rh_2-x Cr_x O₃ particles was decreased further, it is difficult to load ultrafine (<2 nm) Rh_2-x Cr_x O₃ particles onto a photocatalyst by using conventional loading methods. In this study, a new loading method was successfully established and was used to load Rh_2-x Cr_x O₃ particles with a size of approximately 1.3 nm and a narrow size distribution onto a BaLa₄ Ti₄ O₁₅ photocatalyst. The obtained photocatalyst exhibited an apparent quantum yield of 16 %, which is the highest achieved for BaLa₄ Ti₄ O₁₅ to date. Thus, the developed loading technique of Rh_2-x Cr_x O₃ particles is extremely effective at improving the activity of the water-splitting photocatalyst BaLa₄ Ti₄ O₁₅ . This method is expected to be extended to other advanced water-splitting photocatalysts to achieve higher quantum yields.