Perfluorooctanoic acid (PFOA) persists in the natural environment because of its chemical stability, exhibit carcinogenicity and endocrine disrupting potential, and has been found to accumulate in wildlife and humans. Unfortunately, past studies suggest that traditional water treatment processes including chemical oxidation are not effective in breaking strong C-F bond (485 kJ mol-1) in PFOA. We here report a single-atom Pt-loaded SiC (Pt1/SiC) photocatalyst that exhibits exceptional photocatalytic performance for C-F bond activation and subsequent PFOA degradation. Pt1/SiC was synthesized through a facile, scalable wet-chemical method based on anchor-site and photoreduction techniques, by which we achieved highest single-atom Pt loading (up to 1.6 wt%) reported to date. The high catalytic activity of Pt1/SiC is attributed to effective hydrogen spillover from isolated Pt to the SiC surface where enhanced Si-H bond formation leads to C-F bond activation via Si-H/C-F substitution (into Si-F/C-H) on SiC surface. The overall mechanism of photoinduced hydrodefluorination involves: (1) transformation of PFOA into perfluoroalkyl radical (CnF2n+1) via Photo-Kolbe decarboxylation (i.e., direct photon attack on terminal carboxylic group); and (2) subsequent transformation of CnF2n+1 into short-chain perfluorocarboxylic acids (PFCAs) via the hydrodefluorination by Si−H/C−F redistribution.

Single-atom platinum on silicon carbide for photocatalytic PFOA degradation

256th National Meeting (2018)

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