Au25-Loaded BaLa4Ti4O15 Water-Splitting Photocatalyst with Enhanced Activity and Durability Produced Using New Chromium Oxide Shell Formation Method

We report herein remarkable improvement of activity and stability of an Au25-loaded BaLa4Ti4O15 water-splitting photocatalyst. We first examined the influence of refining the gold cocatalyst on the individual reactions over the BaLa4Ti4O15 photocatalyst in this water-splitting system. The results revealed that refining the gold cocatalyst accelerates not only the hydrogen generation reaction, but also oxygen photoreduction reaction, which suppresses the H2 generation via photoreduction of protons. This finding suggests that photocatalytic activity will be enhanced if the O2 photoreduction reaction can be selectively suppressed by covering Au25 with a Cr2O3 shell which is impermeable to O2 but permeable to H+. Then, we developed new method for the formation of the Cr2O3 shell onto Au25. Our method utilizes the strong metal–support interaction between them. Water-splitting photoactivity of Au25–BaLa4Ti4O15 was improved by 19 times under an optimized coverage of the Cr2O3 shell. The Cr2O3 shell also elongate...