Nanotubular Cr-doped TiO2 for use as high-temperature NO2 gas sensor

Abstract Realization of highly selective and sensitive sensors for various emission gases at higher temperatures is a demanding task of combustion related applications. One of the challenges in meeting these requirements is to develop nano-structured and smart functional materials to detect and monitor emission gases selectively. This work describes the functionalization of TiO 2 -nanotubular layers for NO 2 -sensing through homogeneously distribution of Cr 3+ -doping. Fully incorporation of Cr into the TiO 2 lattice has been demonstrated by TEM, XPS and XRD analysis. No other oxide phase separation occurred even after annealing at temperatures up to 700 °C. By Cr-incorporation into the lattice, TiO 2 -NTs display p-type semiconducting sensing behaviour. As small as 2.5% Cr-doping of TiO 2 -NTs results in improvement of the high-temperature NO 2 -sensing capability in the temperature range of 300–500 °C and in concentrations between 25 and 100 ppm. Furthermore, the cross-sensitivity to CO has been reduced by doping as demonstrated during the mixed gas detection of NO 2 .

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