title: Degradation mechanism of a high-performance real micro gas sensor, as determined by spatially resolved XAFS.
abstract: Of late, battery-driven high-performance gas sensors have gained acceptability in practical usage, whose atomic-scale structure has been revealed by μ-fluorescence X-ray absorption fine structure analysis. We studied the chemical distribution of Pd species in the Pd/Al2O3 catalyst overlayer in the real gas sensor at various degrees of deterioration. In a freshly prepared sensor, all Pd species were in the PdO form; in a heavily deteriorated sensor, Pd/Al2O3 in the external region changed to metallic Pd particles, while the PdO structure in the inner region near the heater remained unchanged. The Pd species distribution was in agreement with the simulated thermal distribution. Temperature control was crucial to maintain the high performance of the gas sensor. The improved sensor allows homogeneous heating and has a lifetime of more than 5 years.
authors.affiliation: Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo 113-8549, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Wada
authors.forename: Naoyoshi
authors.initials: N
authors.lastname: Murata
authors.forename: Hiromitsu
authors.initials: H
authors.lastname: Uehara
authors.forename: Takuya
authors.initials: T
authors.lastname: Suzuki
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nitani
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Niwa
authors.forename: Motohiro
authors.initials: M
authors.lastname: Uo
authors.forename: Kiyotaka
authors.initials: K
authors.lastname: Asakura