Unraveling the mechanisms of room-temperature catalytic degradation of indoor formaldehyde and its biocompatibility on colloidal TiO₂-supported MnOₓ–CeO₂

Haiwei LI, Tingting HUANG, Yanfeng LU, Long CUI, Zhenyu WANG, Chaofeng ZHANG, Shuncheng LEE, Yu HUANG, Junji CAO, Wing Kei HO

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

This work overcomes the limitations in room-temperature and moisture-dependent activity of transition metal oxide-based catalysts for sub-ppm formaldehyde removal. The active site exposure and self-assembly hydrophilicity were highlighted in MnOₓ–CeO₂ (MCO) nanospheres after the loading of colloidal 2.1 wt% TiO₂ particles (TO–MCO). Approximately 57% (relative humidity = 72%) and 41% (dry air) recycling catalytic activities at 35 °C were achieved. Our results proved that surface electron transfer, which was previously weakened because of the loss of surface oxygen species and unsuitable defect-site depositions of low active ions, in the MCO catalyst was recovered via the dispersion of hydrophilic Ti–O groups. This electron transfer was also strongly correlated with the specific surface area, porosity, and oxidation states of transition metals. The greater active site exposure derived from the cyclic electron transfer eventually enhanced the HCHO chemisorption and participation of oxygen species on the surface of TO–MCO throughout the bimetallic (Mn–Ce) dismutation reactions. The abundant superoxide radicals that were activated by these oxygen species prompted a nucleophilic attack on carbonyl bonds. Direct photoionization mass spectrometry determined formic acid, dioxirane (minor), and HOCH₂OOH (little) as intermediates governing the HCHO selectivity to CO₂. The cytotoxicity of catalysts exposed to yeast cells was evaluated for their potential environmentally friendly application indoors. Copyright © 2018 The Royal Society of Chemistry.
Original languageEnglish
Pages (from-to)1130-1139
JournalEnvironmental Science: Nano
Volume5
Issue number5
Early online dateMar 2018
DOIs
Publication statusPublished - 2018

Fingerprint

Biocompatibility
formaldehyde
Formaldehyde
formic acid
catalyst
transition element
Oxygen
Degradation
electron
oxygen
degradation
Catalysts
Transition metals
Electrons
Photoionization
Catalyst selectivity
Nanospheres
temperature
Formic acid
Hydrophilicity

Citation

Li, H., Huang, T., Lu, Y., Cui, L., Wang, Z., Zhang, C., . . . Ho, W. (2018). Unraveling the mechanisms of room-temperature catalytic degradation of indoor formaldehyde and its biocompatibility on colloidal TiO₂-supported MnOₓ–CeO₂. Environmental Science: Nano, 5(5), 1130-1139. doi: 10.1039/c8en00176f