Evaluation of Ag-based gas-diffusion electrode for two-compartment cell used in novel chlor-alkali membrane process

The oxygen-depolarized cathode has become attractive by reducing energy consumption and also CO2 emissions. The initial gas-diffusion electrode was for a three-compartment cell in which the alkaline electrolyte was separated from the oxygen feeder. During the electrolysis, the electrolyte penetrated into the hydrophobic gas-diffusion layer. Thus the pores in the diffusion layer were flooded with the electrolyte and the performance decreased. We proposed a new gas-diffusion electrode (GDE) having a large pore radius for a two-compartment cell in which the GDE was pressed on the membrane, and the electrolyte was transported through the GDE. The previous electrode was used fora three-compartment cell, which contained the anolyte, catholyte and oxygen-feeder compartments. First, a model analysis was made to simulate the cathodic overpotential curves of the GDE's for the two-compartment and three-compartment cells. Experiments were made using a half cell for the cathodic polarization curve and a zero-gap cell for testing the increased durability. The two-compartment cell with Ag-CC (carbon cloth) had the highest performance among the GDE's. However, the decrease in performance during a longer period, such as 600 days, was considered to be due to catalyst aggregation and not flooding the pores based on the cathodic potential curve and the SEM images. (C) 2011 Elsevier Ltd. All rights reserved.