Lithium metal-mediated electrochemical reduction of per- and poly-fluoroalkyl substances.

Per- and poly-fluoroalkyl substances (PFAS) have substantial environmental and health hazards. Unfortunately, current degradation routes require high temperatures or corrosive conditions and/or lead to incomplete defluorination and the generation of shorter alkyl chains. Inspired by the lithium-metal battery literature, here we develop an electrochemical degradation process that leverages reactive metals and highly reducing environments. We show that electrodeposited lithium metal can enable 95% degradation and 94% defluorination of perfluorooctanoic acid to LiF without forming any shorter C2-C6 PFAS as end products. Using computational simulations, we find that electron transfer from lithium to perfluorooctanoic acid leads to rapid C-F bond cleavage, fluoride formation and carbon chain fragmentation. We expand the scope to other PFAS compounds and demonstrate substantial degrees of degradation on over 22 different PFAS, plus complete mineralization to inorganic fluorides. Finally, we use the mineralized F- as a fluorine source for the synthesis of fluorinated non-PFAS compounds to complete a circular fluorine loop from waste to valuable product.