(237g) Significant Role of Oxygen Dopant in Photocatalytic Pfca Degradation over h-BN
AIChE Annual Meeting
Tuesday, November 16, 2021 - 9:12am to 9:30am
Perfluorocarboxylic acids (PFCAs, CnF2n+1COOH) are among fluorine-rich soil and water resilient contaminants that is practically challenging to be degraded by natural mechanisms including microbiological treatment. Among PFCAs there is perfluorooctanoic acid (PFOA, C7F15COOH), which is known as a dangerous pollutant that causes serious health problems .1 UV-based photolysis has been shown to be able to decompose PFOA, with extremely slow rate making it not quite feasible. Surprisingly, h-BN which is practically an insulator, owing to its very wide bandgap (), was recently shown capable of PFOA decomposition upon irradiation with UV light at room temperature, with an impressive fourfold performance compared to TiO2.2 The of photonic energy provided by irradiation is not sufficient to overcome the huge bandgap of pristine h-BN, yet the photocatalysis is observed. The nature and properties of the active sites, plausible mechanisms and also kinetics of the reaction remain to be explored. Motivated by the recent work by Duan et al.,2 we employ density functional theory to investigate different aspects of degradation of the PFCAs family over h-BN. This work presents a detailed and careful mechanistic study on CF3COOH (Trifluoroacetic acid, the shortest member of PFCAs family) degradation to CFOOH, focusing on the (C(sp3)-F) bond activation. We believe the insight provided by this work can effectively be generalized to understand photocatalytic decomposition of PFCAs with longer carbon chain, particularly PFOA, over h-BN. Our results clearly show the necessity of vacancies and oxygen interstitials to activate h-BN for photocatalytic reactions and more importantly, their ability to facilitate activation of C(sp3)-F bond, which is typically the strongest C-F bond in PFCAs. This study presents vivid theoretical evidence for the significant role of oxygen-filled nitrogen-vacancies, which interestingly promote single-atom photocatalytic PFCA degradation over h-BN.
(1) Environ. Eng. Sci. 2016, 33, 615â649.
(2) Environ. Sci. Technol. Lett. 2020, 7, 613â619.