Inverse-catalyst-effect observed for nanocrystalline-doped tin oxide sensor at lower operating temperatures

Nanocrystalline In2O3-doped SnO2 thin film sensor is synthesized via sol-gel dip-coating technique. This nanocrystalline thin film is successfully utilized to sense hydrogen (H2) gas with the concentration as low as 50 ppm at lower operating temperatures (25-100 °C). For short test-duration (30 min), the H2 sensitivity of the Pt-sputtered sensor is observed to be higher than that of the non-Pt-sputtered film. An “inverse-catalyst-effect” on the H2 gas sensitivity is, however, newly observed when the test-duration is increased to 24 h. The presence of H2O molecules, which remain adsorbed and get accumulated on the sensor surface, during the long test-duration, are primarily attributed to the reduced H2 gas sensitivity of the Pt-sputtered sensors, relative to that of non-Pt-sputtered sensors, at lower operating temperatures (25-100 °C).