Photocatalytic oxygen evolution triggered by photon upconverted emission based on triplet-triplet annihilation.

A visible light responsive photocatalyst, Mo-doped BiVO4 (Mo:BVO), was shown to promote oxygen evolution from water in response to photon upconverted emission based on triplet-triplet annihilation (TTA) in the same aqueous dispersion. Composites comprising a triplet sensitizer (Pt(ii) octaethylporphyrin; PtOEP) and a singlet emitter (9,10-diphenylanthracene; DPA) intercalated in a layered clay compound (montmorillonite or saponite) were prepared using a facile but versatile solvothermal method. These composites were capable of converting green incident light (λ = 535 nm) to blue light (λ = 430 nm) even in air. The host layered clay as well as the co-intercalated surfactant evidently functioned as barriers against water and oxygen to prevent the quenching of the active compounds. The TTA upconversion driven photocatalytic oxygen evolution using the aqueous mixture of the dyes-clay composite and particulate photocatalysts can be a potential approach to eliminate the undesired optical losses and thus be a breakthrough for future industrial and large-scale installation in an inexpensive manner.