In the past years there has been a great interest in self-doped TiO2 nanotubes (blue TiO2 nanotubes) compared to undoped ones owing to their high carrier density and conductivity. In this study, blue TiO2 nanotubes are investigated as photoanode materials for photoelectrochemical water splitting. Blue TiO2 nanotubes were fabricated with enhanced photoresponse behavior through electrochemical cathodic polarization on undoped and annealed TiO2 nanotubes. The annealing temperature of undoped TiO2 nanotubes was tuned before cathodic polarization, revealing that annealing at 500 °C improved the photoresponse of the nanotubes significantly. | Turkish Journal of Chemistry Turk J Chem 2020 44 1642-1654 http chem TÜBİTAK Research Article doi kim-2004-85 Blue TiO2 nanotube arrays as semimetallic materials with enhanced photoelectrochemical activity towards water splitting 1 1 2 Naeimeh Sadat PEIGHAMBARDOUST Umut AYDEMIR 1 Boron and Advanced Materials Application and Research Center Koç University İstanbul Turkey 2 Department of Chemistry College of Sciences Koç University İstanbul Turkey Received Accepted Published Online Final Version Abstract In the past years there has been a great interest in self-doped TiO2 nanotubes blue TiO2 nanotubes compared to undoped ones owing to their high carrier density and conductivity. In this study blue TiO2 nanotubes are investigated as photoanode materials for photoelectrochemical water splitting. Blue TiO2 nanotubes were fabricated with enhanced photoresponse behavior through electrochemical cathodic polarization on undoped and annealed TiO2 nanotubes. The annealing temperature of undoped TiO2 nanotubes was tuned before cathodic polarization revealing that annealing at 500 C improved the photoresponse of the nanotubes significantly. Further optimization of the blue TiO2 nanotubes was achieved by adjusting the cathodic polarization parameters. Blue TiO2 nanotubes obtained at the potential of V vs. SCE with a duration of 10 min exhibited twice more photocurrent response mA cm 2 compared to the undoped TiO2 nanotube arrays mA cm 2 . Oxygen vacancies formed through the cathodic polarization decreased charge recombination and enhanced charge transfer rate therefore a high photoelectrochemical activity under visible light irradiation could be achieved. Key words Blue TiO2 nanotubes cathodic polarization self-doping photoelectrochemical properties water splitting 1. Introduction Recent research activities on water splitting have focused on photocatalyst PC and photoelectrochemical PEC systems. Due
