Evidence of catalytic activation of anatase nanocrystals by vanadium oxide surface layer: Acetone and ethanol sensing properties

TiO2 and TiO2-V2O5 nanocrystals were prepared by coupling sol-gel and solvothermal methods, followed by heat treatment at 400 °C, after which the nanocrystal mean size was still about 5 nm. The materials were used to process chemoresistive sensors, which were tested to ethanol and acetone, with concentrations ranging from 100 to 500 ppm and from 25 to 100 ppm, respectively. The sensing data evidenced that the surface deposition of V2O5 onto the anatase TiO2 nanocrystals enhanced the sensor response up to almost two orders of magnitude for both gases. Moreover, the sensors behavior was completely inverted: with TiO2-V2O5, the highest responses were obtained at the lowest operating temperatures, contrarily to pure TiO2, which required very high operating temperatures. The comparison of the sensing data allowed concluding that the V2O5 deposition effect could be interpreted as a catalytic contribution, in terms of lowered activation energies of the involved reactions and more favored gas adsorption at lower operating temperatures with respect to pure TiO2.