Oxygen reduction electrodes for electrolysis in chlor-alkali cells

Oxygen reduction electrodes, containing non-noble metal catalysts supported on high surface area carbon and wet-proofed with PTFE were tested under reaction conditions for the chlor-alkali electrolysis. Double-layer gas diffusion electrodes were prepared by rolling of an active layer and diffusion layer on a nickel wire screen, compressed and sintered at 300 degrees C. Electrochemical measurements for substantiating the activity and stability of the half-cells were conducted in 8 M NaOH by supplying oxygen at a cell temperature of 70 degrees C and a constant current load of 300 mA cm(-2). An electrolysis cell with a dimensionally stable anode (DSA) and double-layered cathode was assembled, where 4.8 M NaCl and oxygen were supplied, respectively, for the production of chlorine and NaOH. The cell performances as well as stability of the electrodes were investigated at about 80 degrees C. This study shows that by replacing the high voltage consuming hydrogen-evolving reaction and by adopting highly active electrocatalysts as cathode materials, energy savings of more than 30% could be realized. (c) 2005 Elsevier Ltd. All rights reserved.