Tungsten Oxide-Based Z-Scheme for Visible Light-Driven Hydrogen Production from Water Splitting.

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.