Promoted CF4 Decomposition via Enhanced Tricoordinated Al Active Sites

Tetrafluoromethane (CF4), as a typical perfluorocarbon (PFC), has a remarkable global warming potential (GWP) of 7390 and an ultralong lifetime of 50 000 years, making its effective treatment crucial for mitigating environmental impact. Catalytic hydrolysis is a promising way for its effective decomposition, in which Al-based materials have been widely used as efficient catalysts. However, the deficiency of strong Lewis acidic-tricoordinated Al (AlIII) sites strongly limits their catalytic performance. In this work, efficient CF4 decomposition was achieved via promoting AlIII sites over ZnAl2O4 through a facile acid treatment strategy. Among various acid treatments, it was found that H2SO4 treated ZnAl2O4 could achieve 100% CF4 decomposition under a relatively low temperature of 600 °C and kept above 70% removal for over 160 h running. The 27Al magic angle spinning nuclear magnetic resonance (MAS NMR) spectra demonstrated that the proportion of AlIII was increased from ∼0% of the pristine one to 7.5% after H2SO4 treatment. Pyridine-infrared (Py-IR) spectroscopy and NH3 temperature-programmed desorption (NH3-TPD) and CF4-TPD tests indicated that the amount of acid sites and the adsorption capacity of CF4 were dramatically improved after acid treatment. This work proposes a new strategy to improve CF4 decomposition.