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 Au 25 -loaded BaLa 4 Ti 4 O 15 water-splitting photocatalyst. We first examined the influence of refining the gold cocatalyst on the individual reactions over the BaLa 4 Ti 4 O 15 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 H 2 generation via photoreduction of protons. This finding suggests that photocatalytic activity will be enhanced if the O 2 photoreduction reaction can be selectively suppressed by covering Au 25 with a Cr 2 O 3 shell which is impermeable to O 2 but permeable to H + . Then, we developed new method for the formation of the Cr 2 O 3 shell onto Au 25 . Our method utilizes the strong metal–support interaction between them. Water-splitting photoactivity of Au 25 –BaLa 4 Ti 4 O 15 was improved by 19 times under an optimized coverage of the Cr 2 O 3 shell. The Cr 2 O 3 shell also elongated the lifetime of the photocatalysts by preventing the agglomeration of Au 25 cocatalysts.