Due to the excellent thermal and chemical stability, PFCs are widely used in industrial production, for example, in the fields of polymer synthesis, papermaking, textiles, electroplating and fire retardants (Renner, R. Growing Concern over Perfluorinated Chemicals. Environ. Sci. Technol. 2001, 35, 154A-160A; Moody, C. A.; Field, J. A. Perfluorinated Surfactants and the Environmental Implications of Their Use in Fire-Fighting Foams. Environ. Sci. Technol., 2000, 34(18), 3864-3870; and Giesy, J. P.; Kannan, K. Perfluorochemical Surfactants in the Environment. Environ. Sci. Technol., 2002, 36(7), 146A-152A). With the increasing production and use, some PFCs, particularly perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are extensively detected in the environment (water, soil, and dust), and even in the serum and breast milk of human at a high concentration (Giesy, J. P.; Kannan, K. Global distribution of perfluorooctane sulfonate in wildlife. Environ. Sci. Technol., 2001, 35(7), 1339-1342; A. Quantitative Characterization of Trace Levels of PFOS and PFOA in the Tennessee River. Environ. Sci. Technol., 2002, 36(4), 545-551; and Hansen, K. J.; Johnson, H. O.; Eldridge, J. S.; Butenhoff, J. L.; Dick, L. A. Exploring Indirect Sources of Human Exposure to Perfluoroalkyl Carboxylates (PFCAs): Evaluating Uptake, Elimination, and Biotransformation of Polyfluoroalkyl Phosphate Esters (PAPs) in the Rat. Environ Health Perspect., 2011, 119(3), 344-350). This class of substances is persistent pollutants. Research suggests that PFOA and PFOS can cause liver damage, and have genotoxicity, reproductive toxicity, and carcinogenicity. They can be enriched in the food chain, and pose a great threat to human and animal health (Midgette, K.; Peden-Adamsb, M. M.; Gilkesonc, G. S.; Kamenc, D. L. In vitro evaluation of the effects of perfluorooctanesulfonic acid (PFOS) and perfluorooctanoic acid (PFOA) on IL-2 production in human T-cells. J. Appl. Toxicol., 2015, 35, 459-465).
PFCs cannot be degraded by conventional chemical and biological treatment process due to the high C-F reduction potential (F+e−→F−, E0=3.6V) and the large bond energy (Vecitis, C. D.; Park, H.; Cheng, J.; Mader, B. T.; Hoffman, M. R. Treatment technologies for aqueous perfluoro octane sulfonate (PFOS) and perfluorooctanoate (PFOA). Frontiers of Environmental Science & Engineering in China. 2009, 3(2), 129-151). Researchers have proposed many methods for the degradation of PFCs such as electrochemical oxidation, ultrasonic degradation, photocatalytic oxidation, and reduction with hydrated electrons (Moriwaki, H.; Takagi, Y.; Tanaka, M.; Tsuruho, K.; Okitsu, K.; Maeda, Y. Sonochemical Decomposition of Perfluorooctane Sulfonate and Perfluorooctanoic Acid. Environ. Sci. Technol., 2005, 39(9), 3388-3392; Lin, H.; Niu, J. F.; Ding, S. Y.; Zhang, L. L. Electrochemical degradation of perfluorooctanoic acid (PFOA) by Ti/SnO2—Sb, Ti/SnO2—Sb/PbO2 and Ti/SnO2—Sb/MnO2 anodes. Water. Research, 2012, 46(7), 2281-2289; Qu, Y., Zhang, C. J.; Li, F.; Chen, J.; Zhou, Q. Photo-reductive defluorination of perfluorooctanoic acid in water. Water. Research. 2010, 44(9), 2939-2947; and Song, Z.; Tang, H. Q.; Wang, N.; Zhu, L. H. Reductive defluorination of perfluorooctanoic acid by hydrated electrons in a sulfite-mediated UV photochemical system. Journal of Hazardous Materials. 2013, 262, 332-338). In these methods, electrochemical oxidation and reduction with hydrated electrons have a high application prospect. Studies show that the PFCs can be rapidly degraded and mineralized on the anode during degradation by electrochemical oxidation. However, the electrochemical process also suffers from notorious disadvantages, for example, short electrode life and the need for adding a high concentration of background electrolyte during the degradation process. The reduction with hydrated electrons has advantages of thorough degradation for PFCs and high defluorination rate. For example, Chinese Patent Application No. 200910051114.8 published on Nov. 17, 2010, discloses a method for degrading PFCs by defluorination through photoreduction, that is, a method for degrading PFCs by reduction with hydrated electrons produced from KI under irradiation. In the method, the PFCs are placed in a reaction vessel fitted with a UV lamp, then a reductive material is fed to the reaction vessel via a feed port, and the PFCs are degraded and defluorinated by reacting with the reductive material under UV irradiation. Under optimum conditions, the degradation rate for PFOA is nearly 100%, and the defluorination rate is 95% or higher. However, in the degradation of PFCs in this patent, an anaerobic condition is needed, and the reaction solution is required to be alkaline, which increases the treatment cost in effective pollution treatment and reduces the operability considerably. Therefore, there is a need for developing a method for efficiently degrading PFCs, which is convenient for use in practice.