Gas sensing capabilities of TiO₂ porous nanoceramics prepared through premature sintering

Pure and noble metal (Pt, Pd, and Au) doped TiO₂ nanoceramics have been prepared from TiO₂ nanoparticles through traditional pressing and sintering. For those samples sintered at 550 ℃, a typical premature sintering occurred, which led to the formation of a highly porous microstructure with a Brunauer–Emmett–Teller (BET) specific surface area of 23 m²/g. At room temperature, only Pt-doped samples showed obvious response to hydrogen, with sensitivities as high as ~500 for 1000 ppm H₂ in N₂; at 300 ℃, all samples showed obvious responses to CO, while the responses of noble metal doped samples were much higher than that of the undoped ones. The mechanism for the observed sensing capabilities has been discussed, in which the catalytic effect of Pt for hydrogen is believed responsible for the room-temperature hydrogen sensing capabilities, and the absence of glass frit as commonly used in commercial thick-film metal oxide gas sensors is related to the high sensitivities. It is proposed that much attention should be paid to metal oxide porous nanoceramics in developing gas sensors with high sensitivities and low working temperatures.