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

摘要

The oxygen-depolarized cathode has become attractive by reducing energy consumption and also CO_2 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 for a 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.