Enhanced photocatalytic activities of Ta, N co-doped TiO2 thin films under visible light

Ta, N co-doped TiO2 thin films in an anatase form were fabricated by radio-frequency (RF) magnetron sputtering method, and their photoelectrochemical and photocatalytic properties were compared to those of non-doped TiO2 and N-doped TiO2 thin films. The incident photon-to-current conversion efficiency (IPCE) spectra indicated the suppression of the isolated N 2p band formation but the enhancement hybridization of valence band with N 2p band in Ta, N co-doped TiO2, compared to N-doped TiO2. The changes in IPCE spectra in the presence of reductants, such as SCN−, Br− and I−, clearly proved that the holes produced in the N 2p band of Ta, N co-doped TiO2 under visible light had higher oxidation power than those of N-doped TiO2. Moreover, it was shown that the photocatalytic oxidation activity evaluated by the oleic acid decomposition and photoinduced hydrophilic conversion were enhanced by the Ta, N co-doping under visible light, when compared to N single doping. The enhancement of photocatalytic performances by the Ta, N co-doping under visible light was also supported by the first principle calculation, indicating the positive shift of the N 2p band in Ta, N co-doped TiO2, compared to N-doped TiO2.