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

Area of Science:

• Environmental Chemistry
• Materials Science
• Electrochemistry

Background:

• Per- and polyfluoroalkyl substances (PFAS) are persistent organic pollutants due to strong carbon-fluorine bonds.
• Catalytic degradation of PFAS is challenging, necessitating advanced treatment strategies.
• Electrochemical reduction offers a promising pathway for PFAS C-F bond cleavage and defluorination.

Purpose of the Study:

• To develop a comprehensive theoretical framework for screening transition metal (TM) catalysts for PFAS electrochemical degradation.
• To identify effective TM catalysts by incorporating essential electrochemical factors often overlooked in theoretical assessments.
• To evaluate the catalytic potential of 27 TMs across 81 surface facets for degrading perfluorobutanoic acid (PFBA).

Main Methods:

• Development of a rigorous theoretical screening protocol for TM catalysts.
• Inclusion of critical electrochemical factors: hydrogen evolution reaction, surface oxidation, fluorine poisoning, and physisorption exclusion.
• Application of the protocol to assess C-F bond cleavage in PFBA using 27 TMs and 81 surface facets.

Main Results:

• Identification of 14 promising TM surface facets capable of meeting the stringent requirements for PFBA degradation.
• Demonstration that C-F bond cleavage difficulty correlates with electron density accumulation at the carbon site.
• Observation of reduced charge transfer and increased reaction energies in later defluorination steps.

Conclusions:

• The developed screening protocol provides a realistic assessment of TM catalysts for PFAS electrochemical degradation.
• The findings highlight the importance of considering multiple electrochemical factors for effective catalyst design.
• A simple electronic descriptor can predict the energetic challenges in C-F bond cleavage during PFAS defluorination.