Synthesis of cobalt-iron bimetallic nanocrystals supported on mesoporous silica using different templates

CoFe bimetallic samples containing 25 wt% total of metal content were prepared by incipient wetness impregnation of cobalt nitrate and iron nitrate salts over hexagonal mesoporous silica (HMS). A series of HMS silicas have been prepared by a neutral assembly pathway using two types of structure director: dodecylamine (DDA) and tetradecylamine (TDA). The effect of different templates in the formation of HMS mesoporous silica and bimetallic CoFe supported samples has been investigated and characterized by N-2 physisorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), hydrogen chemisorption, thermogravimetric (TGA) and differential thermal (DTA) analyses. The amount of incorporated metal was estimated by atomic absorption spectroscopy (AAS). Also, a series of supported monometallic cobalt/iron samples were synthesized and compared to bimetallic ones. The textural properties revealed a lower percentage decrease in BET area and total pore volume for the CoFe/HMS (DDA) sample. XRD results showed alpha-Fe2O3 phase formation and higher Co3O4/CoFe2O4 crystallite sizes for CoFe/HMS (TDA) sample. The latter also presented lower reduction temperatures and a slightly lower dispersion (%) compared to CoFe/HMS (DDA). (C) 2010 Elsevier B.V. All rights reserved.