Efficient difunctional photocatalyst prepared: In situ from Prussian blue analogues for catalytic water oxidation and visible-light absorption

The photocatalytic water oxidation reaction (WOR) usually requires the use of a noble metal catalyst as well as a photosensitizer, therefore developing new types of non-noble metal and photosensitizer-free catalysts is of great significience for the photocatalytic WOR. In this paper, a facile paradigm for designing photosensitizer-free difunctional catalysts from old fashioned cubic MOFs as Prussian blue analogues (PBAs) is presented. The as-prepared Co(OH)₂-modified CuO (Co(OH)₂/CuO) nanoparticles displayed robust catalytic efficiency (3567 μmol h^-1 g^-1) toward visible-light-driven water oxidation reaction (WOR). Intriguingly, insights into the WOR pathway indicated that the Co(OH)₂/CuO nanoparticles could serve as both water oxidation catalysts and visible light absorption centers and they still showed photocatalytic performance under monochromatic light at 765 nm and maintained 64.2% oxygen evolution compared to the case with light cutting off at 420 nm. The Co(OH)₂/CuO nanoparticles were shown to be quite stable in the reaction system via characterizing their properties before and after the reactions. While the synergetic effect between Co(OH)₂ and the CuO clusters was found to be key to the abnormal photocatalytic activity of this catalyst in the complicated WOR process. We hope that this contribution will serve as a useful template for other researchers to design new transition metal catalysts for WOR.