Abstract
Doping with other elements is one of the efficient ways to modify the physical and chemical properties of TiO2 nanomaterials. In the present work, Ni-doped TiO2 nanotubes were fabricated through anodic oxidation of NiTi alloy and further annealing treatment. The hydrogen sensing properties of the nanotube sensor were investigated. It was found that the Ni-doped TiO2 nanotubes were sensitive to an atmosphere of 1,000 ppm hydrogen, showing a good response at both room temperature and elevated temperatures. A First-Principle simulation revealed that, in comparison with pure anatase TiO2 oxide, Ni doping in the TiO2 oxide could result in a decreased bandgap. When the oxide sensor adsorbed a certain amount of hydrogen the bandgap increased and the acceptor impurity levels was generated, which resulted in a change of the sensor resistance.
Highlights
There is an ever-increasing demand for gas sensors in various fields [1,2]
We demonstrate that the Ni-doped nanotubes could have a good performance with high sensitivity and quick response in detecting hydrogen atmospheres at room and higher working temperatures
The steady-state stage corresponds to a process with equal dissolution rate and formation rate of doped TiO2 film
Summary
There is an ever-increasing demand for gas sensors in various fields [1,2]. Particular attention has been devoted to the monitoring of hydrogen (H2) mainly due to the wide application of hydrogen gas in either a clean energy source or in many chemical plants. Hydrogen molecules could be chemisorbed into the grain boundaries and pick up electrons from the conduction band to create a space charge layer among the grains This will lead to the formation of Schottky barriers at the grain surfaces and a decrease of conductivity of the oxide materials [6,7,8]. As a wide bandgap n-type semiconductor material, anatase TiO2 (Eg ≈ 3.2 eV) suffers from poor conductivity and this usually causes increased resistance of electronic components when working. It is probably hard for anatase TiO2 to be considered an ideal semiconducting material for wide use in detecting hydrogen gas. We demonstrate that the Ni-doped nanotubes could have a good performance with high sensitivity and quick response in detecting hydrogen atmospheres at room and higher working temperatures
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