Layered tantalum oxynitride nanorod array carpets for efficient photoelectrochemical conversion of solar energy: experimental and DFT insights.

Anodically fabricated tantalum oxide (Ta2O5) nanorod array carpets are converted into the corresponding tantalum oxynitride (TaON) through nitridation in an ammonia atmosphere. The measured optical bandgap energy of TaON is ∼2.3 eV, which is also confirmed via the density functional theory calculations. When used to photoelectrochemically split water (AM 1.5G illumination, 1 M KOH, and 0.6 V applied DC bias), the multilayer nanorod films show visible-light incident photon conversion efficiencies (IPCE) as high as 7.5%. The enhanced photochemical activity is discussed in terms of the ordered one-dimensional morphology as well as the electron effective mass in TaON and Ta2O5.