Solar-Driven Z-scheme Water Splitting Using Modified BaZrO3-BaTaO2N Solid Solutions as Photocatalysts

A two-step photocatalytic water splitting (Z-scheme) system consisting of a modified BaZrO3-BaTaO2N solid solution, a paired photocatalyst and a. reversible donor/acceptor pair (i.e., redox mediator) was constructed BaZrO3-BaTaO2 (Zr/Ta = 0.05) having a band gap of 1.8 eV has sufficient potential to reduce and oxidize water by absorbing, visible photons of up to 660 nm. Upon suitable modification of this material with nanoparticulate cocatalysts, both H-2 and O-2 were evolved individually the presence of reversible redox couples (viz., IO3-/I- and Fe3+/Fe2+), although O-2 evolution from aqueous solution containing Fe3+ was negligible. Among various combinations tested, BaZrO3-BaTaO2N modified with Pt nanoparticles was the most suitable for H-2 evolution in the presence of an IO3-/I- pair, achieving Z-scheme water splitting into H-2 and O-2 in combination with either PtOx/WO3 or TiO2 rutile as an O-2 evolution photocatalyst even under simulated sunlight.