Preparation of carbon nanotube-supported metal nanoparticles coated with silica layers

Carbon nanotube (CNT)-supported Pt metal (Pt/CNT) was covered with silica layers using hydrolysis of 3-aminopropyl-triethoxysilane (APTES) and/or tetraethoxysilane (TEOS). The hydrolysis of APTES resulted in a uniform coverage of Pt/CNT with silica layers, but the silica layers were very thin. Pt/CNT could be coated with silica layers of a few nanometers thickness by hydrolysis of TEOS, but the thickness was not uniform. In contrast, the successive hydrolysis of APTES and TEOS resulted in a uniform coverage of Pt/CNT with silica layers of a few nanometers thickness. Pt metal particles in silica-coated Pt/CNT adsorbed CO chemically despite uniform coverage of Pt metal particles with silica layers. Therefore, silica-coated Pt/CNT demonstrated high catalytic activity in methane combustion.