Ag-promoted Cr/MnO₂ catalyst for catalytic oxidation of low-concentration formaldehyde at room temperature

As one of the significant pollutants in indoor air, formaldehyde (HCHO) has attracted increasing attention due to its negative effects on human health. Thus, to reduce formaldehyde pollution, herein, an Ag-promoted Cr/MnO₂ catalyst (Ag/Cr/MnO₂) was obtained via a hydrothermal-calcination method, which was employed for the catalytic oxidation of low-concentration indoor HCHO (∼1 ppm) at room temperature. The Ag/Cr/MnO₂ catalyst eliminated approximately 98.62% HCHO within 14 h and maintained a high removal efficiency continuously under the dynamic test conditions. Furthermore, the catalyst exhibited good recycling stability and outstanding activity in a humid environment. Different characterization techniques were utilized to determine the physicochemical properties that contribute to improving the catalytic performance. The Ag substance contained metallic Ag (Ag⁰) as the main component and some Ag₂O, and the Ag⁰ particles provided ample active sites for the catalytic oxidation of HCHO. Besides, the incorporation of Ag increased the reducibility of the catalyst and the content of Mn⁴⁺, Cr⁶⁺ and oxygen vacancies. The abundant active sites, high reducibility, rich Mn⁴⁺, Cr⁶⁺, oxygen vacancies, and surface lattice oxygen species, and the powerful interaction between Cr/MnO₂ and Ag were the reasons for the splendid catalytic capability for HCHO by the Ag/Cr/MnO₂ catalyst. In conclusion, the Ag/Cr/MnO₂ catalyst can be a promising catalyst to degrade HCHO with practical application significance.