Trichlorofluoromethane (CFC 11) and 1,1,2-trichloro-1,2,2-trifluoroethane (CFC 113) have been cathodically reduced in a laboratory-scale flow cell at room temperature. The electrodes, 10 cm(2) in section, were a Cu cathode and a H-2-fed gas diffusion electrode. The cell reservoir contained 0.5 dm(3) of methanol-water mixture with NH4Cl, perchlorate of tetrabutylammonium (PTBA), or both. In the case of CFC 113, 50 ppm PdCl2 was also added to the electrolyte. Electroreduction took place with the formation of dechlorinated derivatives by steps, methane and difluoroethene being the last derivatives for CFCs 11 and 113, respectively. The current efficiency in NH4Cl was about 75%. It was improved for CFC 11 to 90-95% when PTBA was employed, both with NH4Cl or alone. The use of PTBA for CFC 113 was unsatisfactory, because it interfered with Pd electrodeposition and the current efficiency decreased. However, copper corrosion during the electroreduction of both CFCs significantly decreased with the use of PTBA. The hydrogen diffusion anode appeared to be chemically stable during the process, although some concave deformation after prolonged hydrogen oxidation leading to an increase in the interelectrode gap was apparent. The improvement of its dimensional stability is discussed. (C) 2004 The Electrochemical Society.