Facile synthesis of ZnO-SnO2 hetero-structured nanowires for high-performance NO2 sensing application

Abstract

A facile strategy was designed to synthesize ZnO-SnO 2 hetero-structured nanowires followed by comprehensive studies on their sensing properties and mechanism. • ZnO-SnO 2 hetero-structured nanowires were designed and synthesized for NO 2 sensing. • ZnO-SnO 2 heterostructures were composed of ZnO nanowires and the surface-loaded SnO 2 nanoparticles. • ZnO-SnO 2 heterostructures showed overall superior sensing performance to NO 2 compared with pure ZnO nanowires. • The possible sensing enhancement mechanisms were discussed. SnO 2 nanoparticles were uniformly grown on the surfaces of ZnO nanowires by a simple hydrothermal process to form one-dimensional ZnO-SnO 2 hetero-structured nanowires. The morphology, microstructure, and composition of the pristine ZnO and ZnO-SnO 2 hetero-structured nanowires were characterized by X-ray diffraction, scanning and transmission electron microscopies and X-ray photoelectron spectroscopy. A systematic investigation on their gas sensing characteristics was performed using a static gas sensing measurement system. The ZnO-SnO 2 hetero-structured nanowires exhibited an overall enhancement in NO 2 sensing properties, which was found to be closely related to their Sn/Zn atomic ratio. The highest NO 2 response was obtained for ZnO-SnO 2 hetero-structured nanowires with Sn/Zn atomic ratio of 5% and at operating temperature of 150 °C. Compared with pristine ZnO nanowires, these hetero-structured nanowires also exhibited faster response/recovery rate and better NO 2 selectivity. The difference in sensing performance between pristine ZnO nanowires and ZnO-SnO 2 heterostructures are explained based on the surface depletion model and the potential barrier control model.