Oxygen reduction electrodes in chlor-alkali electrolysis

Oxygen reduction electrodes, containing non-noble metal catalysts supported on high surface area carbon, bonded by PTFE were tested under practical reaction conditions for the chlor-alkali electrolysis. Doublelayer gas diffusion electrodes were prepared by rolling the active layer and diffusion layer on a nickel wire screen. Electrochemical measurements of the half-cells were conducted in 8M NaOH with pure oxygen supply at 80oC and at a constant current load of 300 mA/cm2. Moreover, a cell with a DS anode and doublelayered cathode was assembled, where 4.8M NaCl and pure oxygen were supplied for the production of chlorine and NaOH. Thermodynamics of the half-cell reactions in comparison to the conventional method using hydrogen-evolving cathode, the temperature increase for the reaction, performances as well as stability were investigated. By replacing the high power consuming hydrogen evolving reaction and adopting highly active electrocatalysts as cathode materials, energy savings of more than 30% could be realized. (author)