Determination of Hydrogen Sulphide in Air with an Indium Oxide Semiconductor Sensor

Hydrogen sulfide, a toxic gas, can be released into the air during oil and natural gas extraction, metallurgical production, and the storage and processing of industrial and household wastes. The determination of hydrogen sulfide in the atmosphere is a pertinent task in analytical chemistry. The established methods, such as chromatography or mass spectrometry, are unsuitable for continuous monitoring in hard-to-reach places. This creates a practical need for a low-cost chemical sensor that offers high sensitivity and selectivity. In this study, gas-sensitive materials based on In₂O₃ with catalytic additives—primarily palladium (as PdO) and silver (as Ag₂O)—were synthesized. The synthesis proceeded in several stages. Initially, an In(OH)₃ sol was prepared, followed by centrifugation and thermal treatment to yield indium oxide nanopowder. The material was characterized by transmission electron microscopy (TEM) and X-ray powder diffraction. Subsequently, the indium oxide nanopowder was blended with catalytic additives and a binder to form a paste. The gas-sensitive material was obtained by annealing the paste at 750°C. The sensor properties of these gas-sensitive materials were investigated with respect to hydrogen sulfide and carbon monoxide under nonstationary temperature conditions: heating to 450°C for 2 s and cooling to 100°C for 13 s. The study demonstrated that nanodispersed indium oxide-based materials exhibit high sensitivity to hydrogen sulfide and exceptional selectivity.