Oxygen vacancy enabled mesoporous Mn–Co oxide material for high-performance formaldehyde sensor worked at room temperature

Abstract

In recent years, the exploration of hazardous gases at room temperature (RT) has remained one of the key focuses in the research field of the semiconductor gas sensors. Herein, mesoporous manganese-cobalt (Mn–Co) oxides with abundant oxygen vacancies were synthesized by the combustion method assisted with the green reducing agent l-Ascorbic acid (LA). The synthesized Mn–Co oxides were performed by X-ray spectroscopy (XPS) and Raman spectrometer to research their chemical state of surface elements. The results manifested that the Mn–Co oxides with LA adding during preparation possessed abundant oxygen vacancies. Additionally, the gas sensitivity tests indicated that the Mn–Co oxides with a mole ratio of LA to metal elements (MCO-0.3L) exhibited best formaldehyde sensing properties compared to other prepared Mn–Co oxides in the concentration of 0.25–30 ppm at RT. Notably, its response to 5 ppm formaldehyde at RT was more than 7 times of that of the Mn–Co oxides prepared without LA adding (8.1 vs 1.1). The MCO-0.3L sensor has a limit of detection (LOD) as low as 5.2 ppb. It also showed good selectivity and reliability. The improved formaldehyde sensitivity of the Mn–Co oxides sensors is supposed as the synergistic action of the abundant oxygen vacancies and the mesoporous structure.