Synthesis and density functional theory study of free-standing Fe-doped TiO2 nanotube array film for H2S gas sensing properties at low temperature

Abstract To analyze the sensing performance of the TiO2 nanotube (TiNT) array film gas sensor to H2S at low working temperature, the free-standing Fe-doped TiNT array films were synthesized using the one-step anodic oxidation method followed by immersion and annealing processes. The results obtained from the field emission scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectra and ultraviolet-visible spectra methods indicate that the lattice of TiO2 was doped by iron ions. Subsequently, compared with undoped TiO2, the response intensity, response and recovery times of the gas sensor based on Fe-doped TiNT array film to 50 ppm H2S at 100 °C were improved. Furthermore, the improved selectivity and stability to H2S were also obtained with the Fe-doped TiNT gas sensor. Finally, based on the Density Functional Theory (DFT), the band structure of Fe-doped TiO2 and the electronic density of states of H2S and the compared gases are calculated and used for the systematical analysis of sensing and selectivity mechanisms of the Fe-doped TiNT gas sensor at low working temperature.