Fabrication of efficient TaON and Ta₃N₅ photoanodes for water splitting under visible light irradiation

Efficient TaON and Ta₃N₅ photoanodes for water splitting were fabricated on conducting glass support (FTO). A necking treatment, which forms effective contacts between TaON (or Ta₃N₅) particles, afforded a significant increase in the photocurrent. Furthermore, loading of IrO₂·nH₂O nanoparticles as a cocatalyst for water oxidation improved the photocurrent of the TaON (or Ta₃N₅) photoanode. The incident photon to charge carrier efficiencies (IPCEs) of the TaON and Ta₃N₅ photoanodes were calculated to be ca. 76% at 400 nm and ca. 31% at 500 nm, respectively, at 1.15 V vs. reversible hydrogen electrode (RHE) in aqueous Na₂SO₄ solution. Overall water splitting into H₂ and O₂ under visible light was demonstrated using an IrO₂·nH₂O-loaded TaON (or Ta₃N₅) photoanode combined with a Pt electrode under an externally applied bias (TaON: > 0.6 V, Ta 3 N 5 : > 1.0 V).