Contrasting room-temperature hydrogen sensing capabilities of Pt-SnO₂ and Pt-TiO₂ composite nanoceramics

Contrasting room-temperature hydrogen sensing behaviors have been revealed for Pt-TiO₂ and Pt-SnO₂ composite nanoceramics. In the case of the Pt-TiO₂ nanoceramics, the ultrahigh hydrogen sensitivities are lost abruptly when the oxygen/hydrogen concentration ratio in ambient atmosphere reaches a critical value. However, in the case of the Pt-SnO₂ nanoceramics, such a phenomenon does not occur, and the extraordinary room-temperature hydrogen sensing capabilities are observed in the presence of oxygen in air. Our combined experimental and theoretical investigations establish a unified mechanism for both the systems, which is rooted in hydrogen chemisorption on the surface and interstitial lattice sites of SnO₂ and TiO₂; the difference in stability of the chemisorbed hydrogen on SnO₂ and TiO₂ is considered responsible for the contrasting hydrogen sensing capabilities. The central findings are helpful in enriching our microscopic understanding of hydrogen interaction with various metal oxide semiconductors (MOSs) at room temperature in varying mixed gaseous concentrations, and they could be instrumental in developing reliable room-temperature hydrogen sensors based on bulk MOSs.