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 elongated the lifetime of the photocatalysts by preventing the
agglomeration of Au25 cocatalysts.
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