Bimetallic organic framework-derived SnO2/Co3O4 heterojunctions for highly sensitive acetone sensors

Abstract

Porous structures and heterogeneous compositions are highly desirable to achieve improved sensing performance. Herein, a SnO₂/Co₃O₄ composite with catalytic sites and abundant oxygen vacancies has been successfully synthesized by pyrolyzation of Sn- and Co-based bimetallic organic frameworks (bMOFs). The composites demonstrate desirable p–n heterojunctions, which was confirmed by diffuse reflection ultraviolet–visible spectroscopy (DRS) and Mott–Schottky (M–S) plots. Gas-sensing experiments reveal that the response of SnO₂/Co₃O₄ composites (Sn/Co = 2 : 1, atomic ratio) reaches 498 to 50 ppm acetone, which is about 5 times higher than that of the pure SnO₂. Moreover, the composites exhibit better selectivity and stability at an operating temperature of 275 °C. This excellent performance is attributed to the synergistic effect of catalysis of Co³⁺ and the formation of p–n heterojunctions at the interface between Co₃O₄ and SnO₂.