Photoelectrochemical H evolution on WO/BiVO enabled by single-crystalline TiO overlayer modulations.

Tungsten oxide/bismuth vanadate (WO/BiVO) has emerged as a promising photoanode material for photoelectrochemical (PEC) water splitting owing to its facilitated charge separation state differing significantly from single phase materials. Practical implementation of WO/BiVO is often limited by poor stability arising from the leaching of V from BiVO during PEC operations. Herein, we demonstrate that the synthesis of a tungsten oxide/bismuth vanadate/titanium oxide (WO/BiVO/TiO) heterostructure onto a fluorine-doped tin oxide-coated glass substrate through a combined simple hydrothermal-spin coating strategy will advance PEC performance while slowing water oxidation kinetics and improving photostability. We show that surface postmodification with a nanometer-thick layer of (1 0 1) monofacet-selective single-crystalline TiO provides stable photocurrent density, up to 1.04 mA cm at 1.23 V (compared to a reversible hydrogen electrode in 0.5 M NaSO), with excellent quantum efficiency (45% at 460 nm) and long-term photostability (24 h). Interestingly, crystalline TiO activation layers behave differently from previous TiO amorphous layers, blocking surface defects while improving corrosion resistance, photostability, and the electron transfer process. These results indicate a ≈2.5 times enhancement in photoelectrocatalytic activity related to referenced WO/BiVO photoanodes, encouraging the use of single-crystalline TiO modulations to develop a range of materials for PEC/photocatalytic applications.