Abstract
The stoichiometric water splitting using a solar-driven Z-scheme approach is an emerging field of interest to address the increasing renewable energy demand and environmental concerns. So far, the reported Z-scheme must comprise two populations of photocatalysts. In the present work, only tungsten oxides are used to construct a robust Z-scheme system for complete visible-driven water splitting in both neutral and alkaline solutions, where sodium tungsten oxide bronze (Na(0.56)WO(3-x)) is used as a H(2) evolution photocatalyst and two-dimensional (2D) tungsten trioxide (WO(3)) nanosheets as an O(2) evolution photocatalyst. This system efficiently produces H(2) (14 μmol h(-1)) and O(2) (6.9 μmol h(-1)) at an ideal molar ratio of 2:1 in an aqueous solution driven by light, resulting in a remarkably high apparent quantum yield of 6.06% at 420 nm under neutral conditions. This exceptional selective H(2) and O(2) production is due to the preferential adsorption of iodide (I(-)) on Na(0.56)WO(3-x) and iodate (IO(3)(-)) on WO(3), which is evidenced by both experiments and density functional theory calculation. The present liquid Z-scheme in the presence of efficient shuttle molecules promises a separated H(2) and O(2) evolution by applying a dual-bed particle suspension system, thus a safe photochemical process.