Oxygen vacancy–rich K-Mn3O4@CeO2 catalyst for efficient oxidation degradation of formaldehyde at near room temperature

• Published in: Journal of colloid and interface science 2025-01, Vol.677 (Pt B), p.417-428
• Main Authors: Xing, Gang, Liu, Xuan, Jia, Yazhen, Wu, Jialin, Chai, Liming, Zhai, Wenjie, Wu, Zhaojun, Kong, Jing, Zhang, Jianbin
• Format: Article
• Language: English
• Subjects: Active oxygen species; Formaldehyde; K-Mn3O4@CeO2; Oxygen vacancies; Room temperature degradation
• ISSN: 0021-9797; 1095-7103; 1095-7103
• DOI: 10.1016/j.jcis.2024.08.085

[Display omitted] •Oxygen vacancy-rich K-Mn3O4@CeO2 catalyst.•Excellent catalytic oxidation activity for HCHO at near room temperature.•Addition of K species influences the chemical valence state of Mn from +4 to +8/3.•Lower oxygen vacancy formation energy and adsorption energy for aqueous HCHO solution.•The possible HCHO catalytic oxidation pathway on the K-Mn3O4@CeO2 catalyst. Synthesis of catalysts with high catalytic degradation activity for formaldehyde (HCHO) at room temperature is highly desirable for indoor air quality control. Herein, a novel K-Mn3O4@CeO2 catalyst with excellent catalytic oxidation activity toward HCHO at near room temperature was reported. In particular, the K addition in K-Mn3O4@CeO2 considerably enhanced the oxidation activity, and importantly, 99.3 % conversion of 10 mL of a 40 mg/L HCHO solution at 30 °C for 14 h was achieved, with simultaneous strong cycling stability. Moreover, the addition of K species considerably influenced the chemical valence state of Mn from +4 (ε-MnO2) to +8/3 (Mn3O4) on the surface of CeO2, which obviously changed the tunnel structure and the number of oxygen vacancies. One part of K species is uniformly dispersed on K-Mn3O4@CeO2, and the other part exists in the tunnel structure of Mn3O4@CeO2, which is mainly used to balance the negative charge of the tunnel and prevent collapse of the structure, providing enough active sites for the catalytic oxidation of HCHO. We observed a phase transition from tunneled KMnO2 to Mn3O4 to tunneled MnO2 with the decreasing K+ content, in which K-Mn3O4@CeO2 exhibited higher HCHO oxidation activity. In addition, K-Mn3O4@CeO2 exhibited lower oxygen vacancy formation and HCHO adsorption energies in aqueous solution based on density functional theory calculations. This is because the K species provide more active oxygen species and richer oxygen vacancies on the surface of K-Mn3O4@CeO2, promote the mobility of lattice oxygen and the room-temperature reduction properties of oxygen species, and enhance the ability of the catalyst to replenish the consumed oxygen species. Finally, a possible HCHO catalytic oxidation pathway on the surface of K-Mn3O4@CeO2 catalyst is proposed.