Nanocrystalline In2O3-based H2S sensors operable at low temperatures

Nanocrystalline In(2)O(3)-based solid solutions, with different concentration of Co, with cubic structure were successfully prepared by a simple route. The as-prepared materials were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The indirect heating structure sensors based on pure and doped In(2)O(3) as sensitive materials were fabricated on an alumna tube with Au electrodes and gas-sensing properties of the sensor elements were measured as a function of concentration of dopant, operating temperature and concentrations of the test gases. The results showed that In(2)O(3) had high response towards H(2)S gas at an operating temperature 150 degrees C, while 2.5 wt.% Co-doped In(2)O(3) sensor exhibited enhance response and selectivity to H(2)S at rather lower operating temperature. Incorporation of platinum further improved the response, selectivity and response time towards H(2)S. Platinum incorporated 2.5 wt.% Co-doped In(2)O(3) (Pt: 0.5 wt.%) was able to detect 10-100 ppm of H(2)S in air at an operating temperature of 100 degrees C. The selectivity of the sensor elements for H(2)S against liquefied petroleum gas (LPG), NH(3) and H(2) gases was studied. The improved gas-sensing properties can mainly be attributed to the selectivity to oxidation of H(2)S and noble metal additive sensitization.