UW-Madison researchers have developed a tandem electrochemical process for the near complete degradation of PFAS. Their process cycles between activation and degradation to avoid over producing radicals. At the anode, sulfate is oxidized to persulfate, which is then activated with iron to a sulfate radical to extract an electron from the perfluoroalkyl chain and initiate the PFAS degradation process. Then, electro-Fenton at the cathode produces hydroxyl radicals that can attack the activated PFAS chain but are not capable of this electron extraction step. These two processes are not typically compatible in an undivided cell. Using a decoupled process mediated by redox active materials, the inventors temporally separate the two electrochemical half reactions in the same cell with high energy efficiency. When cycled, their electrochemical cell can degrade even the more recalcitrant perfluorooctanesulfonic acid (PFOS) molecules effectively.