Synthesis of Tin (II or IV) Oxide Coated Multiwall Carbon Nanotubes with Controlled Morphology

How to obtain tin oxide (SnO or SnO 2 ) coated multiwall carbon nanotubes (MWNTs) by a simple SnCl 2 solution method and finely control the coverage rate and particle size of SnO 2 deposits is reported. We find that the amount of HCl added plays a key role in the synthesis. Without adding HCl, SnO but not SnO 2 coated MWNTs is obtained due to the hydrolysis of the SnCl 2 in water. In the case of adding the minimum amount of HCl, which can completely suppress the hydrolysis, a continuous SnO 2 coating is formed on MWNTs with abundant surface graphitic edges. Due to the inhibition effect of HCl on SnO 2 growth, increasing the amount of HCl added leads to the formation of uniformly dispersed and discontinuous SnO 2 nanoparticles with smaller sizes of 2−4 nm and higher crystallinities on the MWNTs. Surface graphitic edges on MWNT side walls causing high surface energy facilitate the deposition of SnO 2 nanoparticles. For MWNTs with perfect surface structure, few SnO 2 nanoparticles are deposited on the nanotubes and the agglomeration of SnO 2 nanoparticles is prone to happen.