One-Step Rapid and Scalable Flame Synthesis of Efficient WO Photoanodes for Water Splitting.

Photoelectrochemical water splitting is a promising approach for the carbon-free production of hydrogen using sunlight. Here, robust and efficient WO photoanodes for water oxidation were synthesized by the scalable one-step flame synthesis of nanoparticle aerosols and direct gas-phase deposition. Nanostructured WO films with tunable thickness and band gap and controllable porosity were fabricated by controlling the aerosol deposition time, concentration, and temperature. Optimal WO films demonstrate superior water oxidation performance, reaching a current density of 0.91 mA at 1.24 V vs. reversible hydrogen electrode (RHE) and an incident photon-to-current conversion efficiency (IPCE) of ca. 61 % at 360 nm in 0.1 m H SO . Notably, it is found that the excellent performance of these WO nanostructures arises from the high in situ restructuring temperature (ca. 1000 °C), which increases oxygen vacancies and decreases charge recombination at the WO /electrolyte interface. These findings provide a scalable approach for the fabrication of efficient photoelectrodes based on WO and other metal oxides for light-driven water splitting.