Synthesis of N doped titania nanotube arrays photoanode using urea as nitrogen precursor for photoelectrocatalytic application

Addition of urea as nitrogen precursor during synthesis of TiO2 nanotube arrays photocatalyst has been investigated. This study aimed to increase the visible light photo response of TiO2 by applying nitrogen doped titania nanotube arrays (N-TNTAs) for photoanode preparation in the photoelectrocatalytic process. Nitrogen doped titania nanotube arrays (N-TNTAs) was synthesized by a one-step electrochemical anodization method at 50 V for 2 hour, in the electrolyte solution containing water, ammonium fluoride, glycerol and specified amounts of urea as nitrogen precursor followed by annealing at 500°C for 3 h to induce crystallization. Amount of urea (0.1, 0.2 and 0.4 wt%) in electrolyte solution and annealing atmosphere (air and N2) were varied to enhance visible light photo response. SEM analysis showed that TNTAs and N-TNTAs were successfully synthesized with diameters of 64-320 nm but the morphologies did not show a significant difference. The XRD results showed an identical pattern dominated by the anatase phase. The size of N-TNTAs crystallite is larger than the undoped TNTAs. UV-DRS analysis showed that N-TNTAs have smaller bandgap energy. The smallest bandgap energy was obtained 2.84 eV from N-TNTAs using 0.2% urea with N2 gas annealing (N-TNTAs 0.2% U-N2). Measurement of photocurrent density showed better activity under visible light with smaller bandgap energy.