Tomohisa Suzuki

New Catalysts for a Zero-Gap Type Gas-Diffusion Electrode in Chlor-Alkali Membrane Process

Introduction It is expected that the cell voltage in chlor-alkali membrane processes could be greatly reduced by using an oxygen gas-diffusion cathode instead of a conventional hydrogen evolving cathode. To realize this new process, several kinds of electrolysis methods and gas-diffusion electrodes (GDE) have been proposed. A zero-gap type GDE with a two-compartment cell, as schematically drawn in Fig.1, has an advantage to attain good electrolytic performance because the electrodes are able to be placed close to the membrane. It also has a merit for constructing large scale cells because there is no requirement to construct a gas chamber separated from a caustic liquid chamber . It has been confirmed by using the Ag catalyst in a small-sized cell that the durable life time at 4kA m is over 5 years (2.45 V as an averaged cell voltage). However, the cell voltage gradually increased in long-term operation, which could be strongly related to the agglomeration of the Ag catalyst particles. This study deals with an excellent electrolytic performance of Ag and Pd binary catalysts that improve the catalytic activity and also inhibit agglomeration of the catalyst particles.