Nanosized SnO 2 powders were synthesized by using the direct pyrolysis means from SnC 2O 4 .The specimens were characterized by TEM, XRD, TG-DTA, FTIR and BET. TEM and XRD showed that the SnO 2 crystallines were less ...Nanosized SnO 2 powders were synthesized by using the direct pyrolysis means from SnC 2O 4 .The specimens were characterized by TEM, XRD, TG-DTA, FTIR and BET. TEM and XRD showed that the SnO 2 crystallines were less than 8 nm in diameter together with a narrow particle size distribution. BET showed that the surface area of SnO 2 was 115.2 m 2/g. FTIR spectra revealed that the absorptions of Sn—O and —OH bonds in SnO 2 ultrafine powders were red-shifted and broadened. According to the curve of TG-DTA, SnC 2O 4 transformed into SnO 2 completely after being calcined at 250 ℃. Further gas sensing experiments testified that the response and recovery times to C 2H 5OH were shorter than those obtained by the conventional precipitation method.展开更多
Nano-particle Pd/?-Al2O3 monometallic and Pd-Cu/?-Al2O3 bimetall ic catalysts were prepared by solvated metal atom impregnation (SMAI) method. Th e results of XRD measurement indicated that Pd- Cu alloy was formed in ...Nano-particle Pd/?-Al2O3 monometallic and Pd-Cu/?-Al2O3 bimetall ic catalysts were prepared by solvated metal atom impregnation (SMAI) method. Th e results of XRD measurement indicated that Pd- Cu alloy was formed in the bim etallic catalysts and the crystalline particle size of the alloy increased as Cu contents increased with average diameters < 6.0nm for all the samples. XPS and Auger spectra showed that Pd was in zero- valent state, Cu existed mainly in z ero- valent state and partially in monovalent state Cu+. The Pd/?-Al2O3 and Pd-Cu/?-Al2O3 catalysts exhibited higher activity for CO oxidation at low temperature. The activity of Pd-Cu/?-Al2O3 bimetallic catalyst was hig her than that of Pd/?-Al2O3 monometallic catalyst. The Pd-Cu/?-Al2O3 c atalyst with Pd/Cu atomic ratio of 1∶1 showed the highest activity.展开更多
文摘Nanosized SnO 2 powders were synthesized by using the direct pyrolysis means from SnC 2O 4 .The specimens were characterized by TEM, XRD, TG-DTA, FTIR and BET. TEM and XRD showed that the SnO 2 crystallines were less than 8 nm in diameter together with a narrow particle size distribution. BET showed that the surface area of SnO 2 was 115.2 m 2/g. FTIR spectra revealed that the absorptions of Sn—O and —OH bonds in SnO 2 ultrafine powders were red-shifted and broadened. According to the curve of TG-DTA, SnC 2O 4 transformed into SnO 2 completely after being calcined at 250 ℃. Further gas sensing experiments testified that the response and recovery times to C 2H 5OH were shorter than those obtained by the conventional precipitation method.
文摘Nano-particle Pd/?-Al2O3 monometallic and Pd-Cu/?-Al2O3 bimetall ic catalysts were prepared by solvated metal atom impregnation (SMAI) method. Th e results of XRD measurement indicated that Pd- Cu alloy was formed in the bim etallic catalysts and the crystalline particle size of the alloy increased as Cu contents increased with average diameters < 6.0nm for all the samples. XPS and Auger spectra showed that Pd was in zero- valent state, Cu existed mainly in z ero- valent state and partially in monovalent state Cu+. The Pd/?-Al2O3 and Pd-Cu/?-Al2O3 catalysts exhibited higher activity for CO oxidation at low temperature. The activity of Pd-Cu/?-Al2O3 bimetallic catalyst was hig her than that of Pd/?-Al2O3 monometallic catalyst. The Pd-Cu/?-Al2O3 c atalyst with Pd/Cu atomic ratio of 1∶1 showed the highest activity.
