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

The stoichiometric water splitting using a solar-drivenZ-schemeapproach is an emerging field of interest to address the increasingrenewable energy demand and environmental concerns. So far, the reportedZ-scheme must comprise two populations of photocatalysts. In the presentwork, only tungsten oxides are used to construct a robust Z-schemesystem for complete visible-driven water splitting in both neutraland alkaline solutions, where sodium tungsten oxide bronze (Na0.56WO3-x ) is used as aH(2) evolution photocatalyst and two-dimensional (2D) tungstentrioxide (WO3) nanosheets as an O-2 evolutionphotocatalyst. This system efficiently produces H-2 (14 & mu;mol h(-1)) and O-2 (6.9 & mu;molh(-1)) at an ideal molar ratio of 2:1 in an aqueoussolution driven by light, resulting in a remarkably high apparentquantum yield of 6.06% at 420 nm under neutral conditions. This exceptionalselective H-2 and O-2 production is due to thepreferential adsorption of iodide (I-) on Na0.56WO3-x and iodate (IO3 (-)) on WO3, which is evidencedby both experiments and density functional theory calculation. Thepresent liquid Z-scheme in the presence of efficient shuttle moleculespromises a separated H-2 and O-2 evolution byapplying a dual-bed particle suspension system, thus a safe photochemicalprocess.