Theoretical Guidelines for Electrochemical C-F Bond Cleavage in Perfluorobutanoic Acid Using Transition Metal Catalysts.

Per- and polyfluoroalkyl substances (PFAS) are persistent pollutants with highly stable carbon-fluorine bonds, which makes catalytic degradation difficult. Among various catalytic strategies, electrochemical reduction has emerged as a practical alternative because it promotes C-F cleavage and H/F exchange. Transition metals (TMs) are particularly attractive for this process, since their conductivity and d-orbitals facilitate electron transfer into the C-F bond. Yet many theoretical studies overlook essential electrochemical factors; these include the hydrogen evolution reaction, surface oxidation, fluorine poisoning, and physisorption exclusion, and neglecting them limits realistic assessment of TM catalysts for PFAS degradation. Consequently, no theoretical framework exists to systematically screen catalysts under such rigorous constraints. To bridge this gap, we developed a theoretical screening protocol and applied it to 27 TMs, evaluating 81 surface facets. Specifically, this approach evaluates the viability of each metal surface for the electrochemical C-F cleavage in perfluorobutanoic acid (PFBA), chosen as a representative short-chain PFAS. Our screening incorporates all four essential electrochemical criteria, enabling the identification of 14 promising TM surface facets that satisfy the demanding requirements for PFBA degradation. An interesting trend emerging from this screening is that the difficulty of C-F cleavage is closely tied to how effectively electron density accumulates on the reacting carbon site. As defluorination progresses, later cleavage steps show sharply reduced charge transfer and correspondingly higher reaction free energies. This relationship suggests that a simple electronic descriptor can anticipate when C-F cleavage becomes energetically demanding.