Ar Plasma-Treated In₂O₃ Microtubes With Rich Oxygen Vacancies, High Surface Area, and Large Pores for Enhanced Formaldehyde Detection

Abstract

In this article, porous In2O3 microtubes with rich oxygen vacancies, high surface area, and large pores were successfully designed by the hydrothermal method combined with Ar plasma treatment (0, 30, 60, and 90 min). The microstructure/nanostructure and morphologies of the as-prepared samples were analyzed. Furthermore, the gas sensing properties of these samples toward formaldehyde were systematically evaluated and compared. The experimental results indicated that with the prolongation of Ar plasma treatment time, the oxygen vacancies content, the surface area, and the pore size increased, which was consistent with the change trend of sensing properties. In particular, sensor based on In2O3 microtubes treated with Ar plasma for 90 min exhibited unparalleled formaldehyde sensitivity ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{a}/{R}_{g}=186.4$ </tex-math></inline-formula> toward 100 ppm), fast gas response speed (1 s), low detection limit (0.5 ppm), and superior selectivity against other interfering gases at 200 °C. These results introduce a promising principle for the future development of practical gas sensors based on pure oxide semiconductors.