Nanocrystalline In2O3-based H2S sensors operable at low temperatures

Abstract 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 °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 °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.