Designing a Z-scheme system based on photocatalyst panels towards separated hydrogen and oxygen production from overall water splitting

Photocatalytic water splitting on particulate semiconductors is a promising approach for large-scale hydrogen production. However, the mixing of H 2 and O 2 whether through traditional one-step or two-step photocatalytic overall water splitting requires additional steps for their separation, which limits its practical application. Herein, a tandem photocatalytic system consisting of an O 2 -evolution photocatalyst panel and a H 2 -evolution photocatalyst panel is established to address the above issue. The two photocatalyst panels are spatially isolated in an O 2 -evolution compartment and a H 2 -evolution compartment while being electrically linked with the aid of redox couples based on a Z-scheme design. Overall water splitting to produce H 2 and O 2 stoichiometrically was realized with a SrTiO 3 :Rh-based H 2 evolution photocatalyst panel and a BiVO 4 -based O 2 evolution photocatalyst panel as a demonstration. The two photocatalyst panels are aligned in a tandem manner, which allows more efficient utilization of solar irradiation. An apparent quantum efficiency of 0.2% at 420 nm for overall water splitting is obtained after optimization. More impressively, separated H 2 and O 2 evolution can be realized, demonstrating the advantages of the present Z-scheme system based on photocatalyst panels. Based on this tandem system, gases evolved in the ZOWS process can be separated spontaneously.