Electrochemical dechlorination of PCE catalyzed by B₁₂ in homogeneous and heterogeneous systems

Electrochemical dechlorination of harmful perchloroethylene by the homogeneous aquacobalamin (vitamin B_12a) system and heterogeneous lipophilic B₁₂ modified electrode system in neutral to alkaline water under aerobic conditions by controlled-current electrolysis were reported. Aquacobalamin effectively catalyzed the dechlorination of perchloroethylene, converting it into trichloroethylene, dichloroethylene (cis/trans), vinyl chloride and ethylene in neutral to alkaline water. The lipophilic B₁₂ derivative with peripheral propyl ester modification was immobilized with Nafion^® membrane on a carbon electrode by a spin coating method and characterized by SEM-EDX, 3D laser scanning microscopy and cyclic voltammogram analysis. The B₁₂ modified electrode with a high water durability catalyzed the dechlorination of perchloroethylene in alkaline water, effectively affording the corresponding dechlorinated products, trichloroethylene, dichloroethylenes, etc., with the 152 turnover number. The electrolysis of perchloroethylene in a D₂O solvent instead of the H₂O solvent and in the presence of N,N-dimethylformamide-d₇ as a hydrogen radical source in standard alkaline water indicated the involvement of a protonation process for dechlorinated product formation during the electrolysis.