Nitrogen-Doped In2O3 Thin Film Electrodes for Photocatalytic Water Splitting

New visible-light photocatalysts were prepared by doping In2O3 with nitrogen from ethylenediamine (NH2(CH2)2NH2) or ammonium chloride (NH4Cl) as the nitrogen source. Nitrogen-doped In2O3 powder prepared from NH2(CH2)2NH2 shows a rhombic structure and a substitutional N-doping, while the powder prepared from NH4Cl shows a cubic structure and NH x in interstitial sites. N-doping extended the light absorption of In2O3 to the visible region (λ < ∼650 nm), narrowing the band gap from 3.5 eV to approximately 2.0 eV. The photocurrent densities of N-doped In2O3 electrodes are at least double those of undoped In2O3 and approximately 50 times better than N-doped TiO2 electrodes in the visible region, although optimization will be needed to deliver high photocurrents. This present work shows that In2O3 can be suitably doped to produce a promising photocatalyst with improved photoelectrochemical properties for solar hydrogen conversion applications.