Calcination-influenced interfacial structures and gas-sensing properties of multi-walled carbon nanotube–tin oxide p–n heterojunctions

Abstract

Multi-walled carbon nanotube–tin oxide (MWCNT–SnO₂) p–n heterojunctions were synthesized using the SnCl₂ solution method. The influence of the calcination on the interfacial structure was investigated using scanning and transmission electron microscopy, Raman spectroscopy, X-ray diffraction, thermal analysis, and N₂ adsorption–desorption isotherms. The interfacial structure influenced gas-sensing properties were revealed. The heterojunctions calcined at 550 °C under an Ar atmosphere show the strongest interactions between the MWCNTs and SnO₂. The strong interactions favored electron transfer, and also resulted in improved gas-sensing properties. After calcination at 650 °C, the increased pore diameter and pore volume, and the improved crystallinity play key roles in the improvement of gas-sensing properties.