Abstract
Mo-doped TiO2 nanotube arrays are prepared successfully by a combined method of direct current (DC) magnetron sputtering and anodic oxidation. The doping amount of Mo can be modified by changing the number of molybdenum blocks on the Ti target while a Ti–Mo alloy film is prepared by magnetron sputtering on a metal Ti substrate, following a Mo-doped TiO2 nanotube array grown by anodization. Morphology test shows that the doping of Mo could inhibit the phase transition and growth of crystal of TiO2. X-ray photoelectron spectroscopy (XPS) results show that Mo has successfully been embedded in the TiO2 crystal lattice and mainly exists in the valence states of Mo6+. Mo-doping samples show slightly increased visible light absorption as the red shift of TiO2 absorption edge with the band gap dropping from 3.24 to 3.16 eV with 0.5 at.% Mo doping. The enhanced photocurrent is demonstrated for a 0.5 at.% Mo-doped TiO2 electrode. Through photoelectric performance testing under UV-visible light irradiation, the nanotube array film with a Mo-doped content of 0.5% produced the maximum photocurrent density, which is about four times the undoped TiO2 nanotube array film, exhibiting a considerable photoelectric effect gain. The controllable Mo doping TiO2 nanotube array film prepared by this combining technique is expected as a promising material for efficient applications in photoelectric conversion.
Highlights
The efficient utilization of solar energy occupies the essential position for addressing energy and environmental conflicts
The controllable Mo doping TiO2 nanotube array film prepared by this combining technique is expected as a promising material for efficient applications in photoelectric conversion
The fabricated TiO2 nanotube array is observed with an approximate length of 300 nm, rinsed in pure water afterwards, dried with an air stream, and annealed at 500 °C for 2 h under which indicates that Ti–Mo film deposited on the Ti substrate is not completely etched
Summary
The efficient utilization of solar energy occupies the essential position for addressing energy and environmental conflicts. Liao et al [21] found that doping with Mo in a sol-gel method can improve the electrochemical performance of TiO2 This is mainly due to the induction of electrons in the conduction band, as well as oxygen defects including vacancies in the band gap increasing the conductivity. The enhanced photoelectrochemical performance was demonstrated for the Mo-TiO2 nanotubes as photoelectrode This combination of magnetron sputtering and electrochemical oxidation method of preparing doped TiO2 with nanotubular morphology aligned perpendicular to the surface of substrates provides some advantages for carrier transport performance among nanotubes as well as between the interfaces of semiconductor and the metal substrate resulting in accelerated separation of photogenerated carriers
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