NO2 sensing properties of Cr2O3 highlighted by work function investigations

Gas sensing peculiarities of chromium oxide (Cr2O3) nanoparticles, obtained by hydrothermal reaction at moderate temperature and subsequent thermal annealing, were studied. The structure and morphology of the obtained Cr2O3 samples were investigated by X-ray diffraction and transmission electron microscopy techniques. Gas sensing measurements revealed their selective sensitivity to nitrogen dioxide (NO2) at 200 °C relative to carbon monoxide (CO), both in dry and humid air. Higher selectivity towards NO2 is attributed to the material surface reactivity even at low operating temperatures. This property was experimentally highlighted by work function changes, as a complementary investigation method to basic electrical resistance. Thus, it was observed that the surface reactivity of Cr2O3 (calcinated at 1000 °C) towards NO2 is higher compared to CO and less influenced by the relative humidity of the surrounding atmosphere. The present study reveals possible applications in the selective detection of NO2 based on Cr2O3. - Highlights: ► Gas sensing properties of Cr2O3 were studied. ► The structure and morphology of Cr2O3 samples were investigated. ► The selective sensitivity to NO2 both in dry and humid air was revealed. ► In order to explain the sensing behaviour, complementary evaluations were done. ► Work function investigations revealed the gas-sensing properties of p-type Cr2O3.