Evolution of Gold Species in an Au/CeO_2 Catalyst and Its Impact on Activity for CO Oxidation  

作　　者：SUN Yong-an SHEN Yue-nian JIA Mei-lin GUO Jin-ling 

机构地区：[1]College of Chemistry and Chemical Engineering, Inner Mongolia University for Nationalities, Tongliao 028043, P. R. China [2]College of Chemistry and Chemical Engineering, Inner Mongolia University, Hohhot 010021, P. R. China [3]College of Chemistry and Environmental Science, lnner Mongolia Normal University, Hohhot 010020. P. R. China

出　　处：《Chemical Research in Chinese Universities》2010年第3期453-459,共7页高等学校化学研究（英文版）

基　　金：Supported by the National Natural Science Foundation of China(No.20563003);the Inner Mongolia Education Depart-ment Fund(No.NJZY07013)

摘　　要：An Au/ceria（0.44%, mass fraction） catalyst containing gold ions was prepared by a modified deposition precipitation method, and the evolution of gold ions in the catalyst and its influence on the catalysis of CO oxidation were investigated. It was found that the as-prepared catalyst containing gold ions with high valence could fully oxidize CO at -10 ℃ initially but was deactivated gradually at low temperatures during the reaction with CO or treatment by unpurified air. The deactivation of the catalyst during CO oxidation or treatment of it by unpurified air was independent and progressive at low temperatures while the activity of the catalyst at relatively high temperatures was maintained well. During the reaction with CO or treatment by unpurified air, the XPS results indicate that gold species evolved from high valence to low valence and the diffuse reflectance UV-Vis spectra show that high valence gold was reduced to charged gold clusters, gold clusters grew to small gold crystals and small gold crystals grew to large gold particles. Accordingly, the high valence gold corresponded to the activity at low temperatures and the metallic gold was active and relatively stable at high temperatures. The turnover frequencies（TOF） of the catalysts treated by different methods at 273 K decreased with the evolution of gold species from high valence to low valence, no maximum of TOF was observed although gold particles in the catalyst attained to about 2-3 nm during the treatment. An Au/ceria catalyst with a gold load of 0.87% （mass fraction） maintained a good activity for CO oxidation within 18 h at room temperature. The catalysts were characterized via transmitted electronic microscopy（TEM）, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray diffraction（XRD） and BET specific surface area and UV-Vis DRS as well.An Au/ceria（0.44%, mass fraction） catalyst containing gold ions was prepared by a modified deposition precipitation method, and the evolution of gold ions in the catalyst and its influence on the catalysis of CO oxidation were investigated. It was found that the as-prepared catalyst containing gold ions with high valence could fully oxidize CO at -10 ℃ initially but was deactivated gradually at low temperatures during the reaction with CO or treatment by unpurified air. The deactivation of the catalyst during CO oxidation or treatment of it by unpurified air was independent and progressive at low temperatures while the activity of the catalyst at relatively high temperatures was maintained well. During the reaction with CO or treatment by unpurified air, the XPS results indicate that gold species evolved from high valence to low valence and the diffuse reflectance UV-Vis spectra show that high valence gold was reduced to charged gold clusters, gold clusters grew to small gold crystals and small gold crystals grew to large gold particles. Accordingly, the high valence gold corresponded to the activity at low temperatures and the metallic gold was active and relatively stable at high temperatures. The turnover frequencies（TOF） of the catalysts treated by different methods at 273 K decreased with the evolution of gold species from high valence to low valence, no maximum of TOF was observed although gold particles in the catalyst attained to about 2-3 nm during the treatment. An Au/ceria catalyst with a gold load of 0.87% （mass fraction） maintained a good activity for CO oxidation within 18 h at room temperature. The catalysts were characterized via transmitted electronic microscopy（TEM）, inductively coupled plasma optical emission spectrometry（ICP-OES）, X-ray diffraction（XRD） and BET specific surface area and UV-Vis DRS as well.

关 键 词：Gold catalyst CO oxidation UV-Vis DRS XPS Gold valence 

分 类 号：O[理学]