Oxygen-plasma-assisted formaldehyde adsorption mechanism of SnO ₂ electrospun fibers

Abstract

Chemisorbed oxygen acts a crucial role in the redox reaction of semiconductor gas sensors, and which is of great significance for improving gas sensing performance. In this study, an oxygen-plasma-assisted technology is presented to enhance the chemisorbed oxygen for improving the formaldehyde sensing performance of SnO ₂ electropun fiber. An inductively coupled plasma device was used for oxygen plasma treatment of SnO ₂ electrospun fibers. The surface of SnO ₂ electrospun fibers was bombarded with high-energy oxygen plasma for facilitating the chemisorption of electronegative oxygen molecules on the SnO ₂ (110) surface to obtain an oxygen-rich structure. Oxygen-plasma-assisted SnO ₂ electrospun fibers exhibited excellent formaldehyde sensing performance. The formaldehyde adsorption mechanism of oxygen-rich SnO ₂ was investigated using density functional theory. After oxygen plasma modification, the adsorption energy and the charge transfer number of formaldehyde to SnO ₂ were increased significantly. And an unoccupied electronic state appeared in the SnO ₂ band structure, which could enhance the formaldehyde adsorption ability of SnO ₂. The gas sensing test revealed that plasma-treated SnO ₂ electrospun fibers exhibited excellent gas sensing properties to formaldehyde, low operating temperature, high response sensitivity, and considerable cross-selectivity. Thus, plasma modification is a simple and effective method to improve the gas sensing performance of sensors.