Nanostructured VO₂ photocatalysts for hydrogen production

Vanadium dioxide (VO₂) is a well-known semiconductor material with a band gap of 0.7 eV, and is seldom used as a photocatalyst. We report here a new crystal structure for nanostructured VO₂, with body-centered-cubic (bcc) structure and a large optical band gap of ∼2.7 eV, which surprisingly shows excellent photocatalytic activity in hydrogen production. The bcc VO₂ phase exhibited a high quantum efficiency of ∼38.7% when synthesized as nanorods. Using films of the aligned VO₂ nanorods, the hydrogen production rate can be tuned by varying the incident angle of UV light on the films and reaches a high rate of 800 mmol/m²/h from a mixture of water and ethanol under UV light, at a power density of ∼27 mW/cm², allowing possible commercial application of this material as photoassisted hydrogen generators.