Preparation And Properties Of Noble Metals Confined In Mesoporous Silica

Nano noble metals have been widely applied in the field of catalysis. Byloading noble metal in mesoporous silica, the dispersive and size of metal particlescan be controlled by the restriction of pores in mesoporous silca, which willsignificantly enhance their catalytic performance. In this paper, noble metalnanoparticles were confined in the channel of mesoporous silica, and investigated ascatalytic filter of gas sensors and catalytic degradation of organic dye.Herein, the noble nanoparticles were encapsulated in the channels ofmesoporous silica after inner and external surface modification of mesoporous silica.The external and inner surface of mesoporous silica was separately modified withmethyl group and amino group. The purpose of introduction amino into the innersurface is to anchor metal precursors ions in to channels by static electricityinteraction. The ions were then reduced into metal nanoparticles with NaBH4.Samples were characterized with XRD, TEM, FT-IR, and N2absorption. The resultsshowed that metal nanoparticles have been successfully loaded in the channel ofmesoporous silica, which exhibited uniform dispersion and small size (about2nm).It was also found that loading amount of various metals can be controlled byaccommodate precursor concentration.The mesoporous silica loaded with noble metal samples synthesized in ourexperiment were investigated as catalytic filter of gas sensor. CH4was used as targetgas and CO was interfered gas. The selectivity of sensors on CH4/CO was inspectedby changing the operate temperature and gas concentration. It was found that theselectivity (C) of sensors on CH4/CO was raised from0.727to9.28after coating ofcatalytic filter, with selectivity improved about13times. The selectivity tendency offilter loaded with different metals was CPt> CPd> CAu. The enhancement ofselectivity was resulted from the catalytic oxidation of CO into CO2by noble metals, which prevent CO from reaching the sensitive layer of gas sensor. Taking advantageof this, CH4can be detected in a mixture gas containing interfered CO gas.Mesoporous silica loaded with noble metal samples synthesized in ourexperiment was further investigated as catalyst to catalyze reduction of RhB, a kindof organic dye. It was illustrated that RhB cannot be reduced in the absence ofcatalyst. In the presence of catalysts (SBA-15, SBA-16and MCM-41loaded withnoble metals), RhB can be easily reduced by NaBH4. The SBA-15loaded catalystsexhibited better catalytic performance than that loaded on SBA-16and MCM-41.Among all the investigated catalysts, Au-SBA-15showed the best catalytic activity,with RhB reduction rate of98%and K of0.133min-1.