Electrochemical fabrication of lanthanum-doped TiO2 nanotube array electrode and investigation of its photoelectrochemical capability

Highly ordered lanthanum-doped (La-doped) TiO2 nanotube arrays were prepared by electrochemical anodization process on a Ti sheet, followed by cathodic electrochemical process using lanthanum nitrate solution as the La source, and at last were analyzed by SEM, XPS, FTIR, XRD, and DRS characterization techniques. The analytical results demonstrated that the La doping could promoted phase transformation of TiO2 from the anatase to rutile. Red shifted and enhanced absorption intensities of certain peaks in both UV and visible light regions were also observed. Moreover, a new state of Ti3+ was founded after calcinations. The photoelectrochemical results indicated that La doping can significantly enhance the photoconversion efficiency of the TiO2 nanotube array electrode. The maximum photoconversion efficiency was 0.598%, which was obviously more than 2-fold higher than the undoped one (0.257%) under the same supporting electrolyte solution. The photoelectrocatalytic (PEC) degradation result of p-nitrophenol (PNP) was used to investigate the PEC activities of the as-prepared electrode. The La-doped TiO2 nanotube array electrode showed much higher degradation efficiencies (99.33%) than the undoped TiO2 nanotube array electrode (70.16%) under the same condition. (c) 2013 Elsevier Ltd. All rights reserved.