Z-scheme water splitting under visible light irradiation over powdered metal-complex/semiconductor hybrid photocatalysts mediated by reduced graphene oxide

Abstract

A powdered Z-scheme system for the photocatalytic water splitting reaction under visible light irradiation was successfully demonstrated utilizing a combination of a metal-complex catalyst, reduced graphene oxide (RGO), and semiconductor photocatalysts. A Ru-complex electrocatalyst, [Ru (2,2′-bipyridine)(4,4′-diphosphonate-2,2′-bipyridine)(CO)₂]²⁺, linked with SrTiO₃ : Rh (Rh: 4 at%) as a H⁺ reduction photocatalyst was coupled with BiVO₄ as a water oxidation photocatalyst and RGO as a solid-state electron mediator. H₂ and O₂ evolved stoichiometrically under visible light irradiation (λ > 420 nm) and the turnover number for the Ru-complex was calculated to be 450 after 8.5 h of irradiation time, which indicates that this Z-scheme system splits water photocatalytically and the Ru-complex functions as an efficient cocatalyst for hydrogen evolution by water splitting.