Unraveling the mechanism of binary channel reactions in photocatalytic formaldehyde decomposition for promoted mineralization

• Published in: Applied catalysis. B, Environmental Environmental, 2020-01, Vol.260, p.118130, Article 118130
• Main Authors: Li, Jieyuan, Cui, Wen, Chen, Peng, Dong, Xing’an, Chu, Yinghao, Sheng, Jianping, Zhang, Yuxin, Wang, Zhiming, Dong, Fan
• Format: Article
• Language: English
• Subjects: Activation energy; Air pollution; Carbon dioxide; Carbon monoxide; Catalytic activity; Construction materials; Decomposition; Decomposition reactions; Degradation; Efficiency; Formaldehyde; Formaldehyde degradation; In situ DRIFTS; Indoor air pollution; Indoor environments; Mineralization; Organic compounds; Photocatalysis; Reaction mechanisms; Reaction pathways; Selectivity; VOCs; Volatile organic compounds
• ISSN: 0926-3373; 1873-3883
• DOI: 10.1016/j.apcatb.2019.118130

[Display omitted] •The reaction mechanism for over-all HCHO degradation was clarified.•The special binary channel reactions in HCHO decomposition have been firstly discovered and proposed.•Highly enhanced degradation efficiency and elevated selectivity for complete mineralization are simultaneously realized. Formaldehyde (HCHO), as one of the major volatile organic compounds emitted from industry activities and construction materials, contributing to both urban and indoor air pollution. In order to unravel the reaction mechanism to enhance the over-all HCHO decomposition efficiency and provide solid evidences to clarify the relationship between photocatalytic activity and reaction pathways, a combined experimental-theoretical approach has been developed in this work. By combining the active radical detection, in situ characterization technology and activation energy calculations, the special binary channel reactions in HCHO decomposition have been firstly discovered and proposed. Two separated reaction pathways are observed, including the pathway I of HCHO → HCOOH → H2CO3 → CO2 and pathway II of HCHO → HCOOH → CO → H2CO3 → CO2. HCOOH is the primary intermediate before HCHO can be completely oxidized into CO2, while the generation of CO is rare. It is found that the HCHO degradation efficiency is directly related to the activation energy of HCOOH transformation. By tailoring the binary channel reaction pathways and rate-determining step, highly enhanced degradation efficiency and elevated selectivity for complete mineralization are simultaneously realized. This work establishes a new method to investigate the reaction pathways for elevating the photocatalysis performance in volatile organic compounds degradation.