Modification of carbon nanotube surfaces with precious metal and transition metal oxide nanoparticles using thin silica layers

• Thin silica layers were formed on CNT surfaces using 3-aminopropyltriethoxysilane.
• Thin silica layers on CNTs stabilize Pt metal particles smaller than 2 nm.
• Pt metal on CNT with very thin silica layers is electrochemically active.
• CNT surfaces with silica layers can be covered with transition metal oxide layers.

The surfaces of carbon nanotubes (CNTs) were covered with thin silica layers through the application of 3-aminopropyltriethoxysilane (APTES) in order to enhance the deposition of precious metal and transition metal oxide nanoparticles. Pt metal particles smaller than 2 nm in diameter could be deposited, using a conventional impregnation method, on CNTs coated with silica layers, whereas Pt particles supported on bare CNT surfaces were approximately 3 nm in diameter. Thus, coating CNTs with thin silica layers enhanced the catalytic activity of the Pt catalysts. In addition, CNTs with thin silica layers could be uniformly covered with transition metal oxide layers (ZrO2, Nb2O5 and Ta2O5) by hydrolysis of the corresponding metal alkoxides. In contrast, metal oxides were very difficult to deposit on bare CNTs. The thin silica layers produced on the CNTs via the use of APTES evidently function as adsorption sites for precursor metals and metal oxides, as well as nucleation sites for metals and metal oxides, allowing the formation of precious metal-CNT and transition metal oxide-CNT composites.

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