The Study of Silver-catalyst of the Gas-diffusion Electrode for Chlor-alkali Electrolysis

Abstract

In order to save the energy for chlor-alkali electrolysis, the gas-diffusion has been investigated. We studied efforts of size and quantity of the silver-catalyst in electrode on the performance of electrodes. We used the fine powder of silver as size of 0.1≫1.0 µm. The performance of the electrodes prepared was evaluated by the measurement of the potential for the oxygen reduction in 32% NaOH at 80°C and 1 atm O₂. The condition of silver-catalyst in electrode prepared was evaluated by SEM images and specific resistance. It was found that the electrode prepared with the size of 0.3 µm as silver-catalyst showed the highest performance and that the catalyst of this electrode was found most dispersed by SEM images. Finally, from this date it was believed that the great number of three-phase zone was formed by the dispersing effect and the best condition to prepare the maximum three-phase zone was found to be 2 mg/cm² Ag. Less than this amount, the performance was lower, maybe due to the lowered number of the points of three-phase zone. On the other hand, when the electrode was loaded more than 17 mg/cm² Ag, the performance also lowered, probably because the surface of the electrode had hydrophilicity. It was concluded that the best condition to prepare the oxygen reduction electrode for chlor-alkali electrolysis was to load 2 mg/cm² Ag whose size was 0.3 µm and with this electrode, the electrolysis was taken place at 2.2 V-0.3 A/cm².