Synthesis and characterization of transition metal and metal oxide nanoparticles inside mesoporous carbon CMK-3

Abstract

Transition metal oxides were synthesized inside the pore system of mesoporous carbon CMK-3. By a wet impregnation, drying and calcination procedure iron, copper, nickel, cobalt, manganese and zinc oxides were formed almost exclusively within the mesopores. A reduction into the metal forms with regard to structural array in the case of zinc oxide and a reduction to manganese(II) oxide for manganese(IV) oxide was accomplished by hydrogen. Powder X-ray diffraction (PXRD), Raman spectroscopy and transmission electron microscopy (TEM) proved the preservation of the host structure during impregnation and reduction procedures. The formation of nanosized metal oxides inside the mesopore system was confirmed with PXRD and TEM. Nitrogen physisorption measurements still revealed micro- and mesoporosity for the host/guest compounds. A reduction of the surface areas and pore sizes in contrast to the host structure being an indication of the coating of the inner surfaces of the carbon walls is shown as well. Infrared and X-ray absorption spectroscopy (XAS) carried out in fluorescence mode confirm the formation of the respective oxides and metals. Furthermore, the existence of small, disordered nanoparticles was proved by XAS investigations and information on the local structure of the metals and metal oxides was obtained from these measurements.