Gas sensing capabilities of TiO2 porous nanoceramics prepared through premature sintering

Abstract

Pure and noble metal (Pt, Pd, and Au) doped TiO 2 nanoceramics have been prepared from TiO 2 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 m 2 /g. At room temperature, only Pt-doped samples showed obvious response to hydrogen, with sensitivities as high as ~500 for 1000 ppm H 2 in N 2 ; 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.

Nanowires-assembled WO3 nanomesh for fast detection of ppb-level NO2 at low temperature

“…Triple-shelled WO 3 spheres synthesized by ultrasonic spray pyrolysis showed a large resistance (>1 GΩ) when exposed to NO 2 gas at low operating temperature [16]. A general strategy to solve this problem is surface functionalization with noble metals (Au, Ag, and Pt) [8,[17][18][19][20]. Gao's group reported Ag-loaded mesoporous WO 3 showed excellent response to NO 2 at 75 ℃ [17].…”

Room-Temperature Hydrogen-Sensing Capabilities of Pt-SnO2 and Pt-ZnO Composite Nanoceramics Occur via Two Different Mechanisms

“…For both kinds of composite nanoceramics, there is no noticeable shrinkage in diameter after sintering. As a matter of fact, densification should be avoided for the sintering of ceramics intended for gas-sensing applications [ 5 ].…”

“…However, they all have to work at elevated temperatures (~500 °C) [ 1 ], which leads to increased energy consumption, shortened service life, and increased safety risks [ 2 ]. In order to develop room-temperature metal oxide (MOX) gas sensors, nano-materials of various MOXs have been synthesized and impressive room-temperature gas-sensing capabilities have been observed for many of them, including SnO 2 [ 3 ], TiO 2 [ 4 , 5 ], WO 3 [ 6 ], Fe 2 O 3 [ 7 , 8 ], ZnO [ 9 , 10 , 11 , 12 , 13 , 14 ]. It is generally believed that the large specific surface of nano-structured MOXs is the key for them to be room-temperature gas sensitive.…”

Study on the Electronic Structure and Enhanced Photoelectrocatalytic Performance of RuxZn1-xO/Ti Electrodes

“…However, the high recombination rate of photogenerated electron-hole pairs and oversized band gap have significantly limited its application. Hence, how to reduce the recombination rate and enlarge the light-absorption area have received much attention [11,12].…”

“…Under its effect, the aforementioned recombination rate was reduced, and more electrons and holes were allowed to participate in the reaction of oxidative cracking of organic dye as the photogenerated electrons were forced to move to the counter electrode through an external circuit, while the holes remained in the valence band thanks to the external electric field. In addition, Shaoce et al designed a dual cocatalysts for spatial separation, of which Co-Pi as the outmost hole-transfer layer and Pt as the bottom electron collector and transport layer, thereby photogenerated electrons-holes pairs were separated effectively and twice higher current density was obtained [12]. However, neither the external bias potential nor the electron collector could increase the yield of photogenerated electron-hole pairs, the light-absorption range was still relatively narrow.…”