Catalytic oxidation of dichloromethane over phosphate-modified Co3O4: Improved performance and control of byproduct selectivity by Co3O4 defects and surface acidity

• Published in: Applied surface science Vol. 606; p. 154924
• Main Authors: Xu, Shuang, Ma, Yu-Kun, Zhang, Ke-Feng, Jia, Ai-Ping, Chen, Jian, Luo, Meng-Fei, Wang, Yu, Lu, Ji-Qing
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 30.12.2022
• Subjects: Chlorinated volatile organic compounds; Cl-containing byproducts; Co-based catalysts; Phosphate modification; Reaction mechanism; Co-based catalysts; Reaction mechanism; Cl-containing byproducts; Phosphate modification; Chlorinated volatile organic compounds
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2022.154924

[Display omitted] •Phosphoric acid etching created more oxygen vacancies on Co3O4.•Phosphate modification on Co3O4 generated strong surface acid sites.•Phosphate modified Co3O4 were highly active and stable for CH2Cl2 oxidation.•Phosphate modified Co3O4 produced negligible Cl-containing organic byproducts. The catalytic oxidation of chlorinated volatile organic compounds (CVOCs) is an important topic in environmental catalysis, but the design of highly effective catalysts remains challenging. In this work, phosphate – modified Co3O4 oxides gave higher activity, better durability and much lower selectivities to Cl-containing byproducts (e.g., CH3Cl and CHCl3) compared to the pristine Co3O4 in the catalytic oxidation of dichloromethane (CH2Cl2). Such phosphate modification created more oxygen vacancies on the Co3O4 and thus enhanced reducibility. On the other hand, the presence of phosphate generated abundant surface Brønsted acid sites and suppressed surface basicity. The improved performance was related to the promoted adsorption/activation of CH2Cl2 on the surface acid sites, and synergistically facile oxidation of the reactive intermediates by the oxygen species activated on the oxygen vacancies. Moreover, on the modified catalyst, the fast oxidation of the reaction intermediate (i.e., CH3O-) inhibited the formation of CH3Cl. Meanwhile, the low surface basicity of the catalyst was probably responsible to the low selectivity to CHCl3.