TEM and XPS studies to reveal the presence of cobalt and palladium particles in the inner core of carbon nanofibers

Abstract

In this paper, the presence of a considerable number of Co (3-4 nm) and Pd (1-4 nm) particles in the inner tube (4-9 nm inner diameter) of carbon nanofibers is demonstrated with TEM and XPS. Oxidation of freshly grown fibers in nitric acid resulted in opening of the inner tube of the fibers and in creating adsorption sites on the internal and external surface of the fibers needed for anchoring of the metal precursors. It is demonstrated that analysis with TEM tilt series is a very powerful tool to locate the actual position of the metal particles, i.e. on the external or internal surface of the fibers. The fraction of metal present in the inner core of the fibers varied from 10-15% for Pd to 28-34% for Co, depending on the synthesis method.

Carbon nanotubes prepared by anodic aluminum oxide template method

“…A knotty problem is that foreign maters may deposit onto the outer surface of CNTs during the filling procedure by using either incipient wetness impregnation method or sublimation method [116,117]. Therefore, the removal of foreign materials from the outer surface of CNTs is required.…”

Hydrotalcites supported on carbon nanofibers as solid base catalysts for the synthesis of MIBK

“…A somewhat smaller mean pore diameter was found with the HT/CNF samples due to coverage of the carbon nanofibers. We attribute the main part of the pore volume to the open space between the cylindrical fibers, although a minor part could be due to the presence of inner tubes [36,37]. Table 1 shows the results derived from nitrogen physisorption of the various HT/CNF materials and HT act .…”

“…The use of a suitable Ni on silica catalyst would be beneficial, because SiO 2 is easily removed in a solution of NaOH. Subsequent treatment of CNF in nitric acid removes exposed Ni and introduces oxygen-containing surface sites [36,37].…”

Supported Hydrotalcites as Highly Active Solid Base Catalysts.

“…20,21 Mg-Al hydrotalcite was deposited on CNF by incipient wetness impregnation of an aqueous solution of Mg(NO 3 ) 2 (1.4 M) and Al(NO 3 ) 3 (0.7 M) and after drying at 393 K followed by impregnation of a solution containing NaOH (8.3 M) and Na 2 CO 3 (0.56 M). After aging for 24 h at 333 K, the material was thoroughly washed and dried at 393 K. Activation of the hydrotalcite materials was performed by heat treatment at 773 K in N 2 flow and rehydration at 293 K with a water-saturated N 2 flow for 72 h. The condensation of acetone (1.8 mol) at 273 K with 1 g of catalyst was analyzed by taking samples over time and analysed with gas chromatography.…”