Development of Energy-saving Process of Chlor-Alkali Membrane Cell with Gas-diffusion Electrode

气体扩散电极氧去极化阴极由于具有节能减排的优点，有望成为纯碱电解的一种优良方法。用氧阴极代替析氢阴极显著降低了电池电压，这是这些电极反应的电势差。使用氧阴极可以节省30 - 40%的能源。然而，使用气体扩散电极的氧阴极尚未实际应用。作为原因之一，当气体扩散电极在高温下在高浓度碱性溶液中使用时，电解液在电解期间渗透到气体扩散电极中的气体供应层。碱性溶液的渗透改变了电极性能，因为在反应位点处的气-液-固相的界面面积减小。氧在气体扩散电极上还原的动力学已被广泛研究，B ...更多信息 但是，由于关于电极特性或电极劣化机理的定量数据不充分，因此还没有获得开发新的气体扩散电极的基本数据。因此，有必要对电极退化进行量化。本研究的目的是提高气体扩散电极在高温高浓度碱性溶液中的稳定性。用交流阻抗法研究了氧在气体扩散电极上还原的阴极特性。用电荷转移电阻和双电层电容定量地测定了电解质对气体扩散电极的渗透作用。比较使用不同寿命的Ag和Pt催化剂的电极，阴极电位和奈奎斯特曲线的直径随着寿命的增加而增加。使用Ag催化剂的电极特性比使用Pt催化剂的电极特性更优异。通过XPS分析气体扩散电极的表面。碳、聚四氟乙烯和银电极表面脱落，吸附钠和氧。通过阴极过电位模拟对电极的劣化机理进行了探讨。薄膜厚度的增加对阴极过电位的增加的影响大于电解质渗透到气体扩散层的影响。少

Oxygen depolarized cathodes with gas-diffusion electrode has been expected as an excellent method for soda electrolysis because of its energy-saving and CO_2-reducing. Replacing hydrogen-evolving cathodes with oxygen cathodes significantly reduces cell voltage, which is the potential difference of these electrode reactions. The use of oxygen cathodes can lead to energy saving of 30 to 40 %. However, oxygen cathodes using gas diffusion electrode have not been practically applied yet. As one of the reasons, when a gas diffusion electrode is used in high concentrated alkaline solution at high temperature, the electrolyte solution penetrates to the gas supply layer in the gas diffusion electrode during electrolysis period. The penetration of the alkaline solution changes the electrode performance because of the decrease in the interface area of the gas-liquid-solid phase at the reaction site. The kinetics of oxygen reduction on a gas diffusion electrode has been extensively investigated, b … More ut basic data in developing the new gas diffusion electrode have not been obtained because of the quantitative data on the electrode characteristic or the mechanism of the electrode degradation are not sufficient. Therefore, it is necessary to have quantification of the electrode degradation. The purpose of this study is to improve the stability of gas-diffusion electrode for high concentrated alkaline solution at high temperature. The cathodic properties of oxygen reduction on the gas diffusion electrode were examined by AC impedance method using an equivalent circuit. The effect of the penetration of the electrolyte into gas diffusion electrode was determined quantitatively by using charge-transfer resistance and the double-layer capacitance. Comparing the electrodes using Ag and Pt catalysts of different life time, the cathode potentials and the diameter of the Nyquist plots were increased with increasing life time. The electrode characteristics using Ag catalyst was more excellent than using Pt catalyst. The surfaces of the gas diffusion electrodes were analyzed by XPS. The surfaces of the electrodes on carbon, PTFE and silver were failed away and adsorbed sodium and oxygen. The mechanism of the electrode degradation was discussed by the cathodic overpotential simulation. The increase of cathodic overpotential was affected by increasing the thickness of the thin-film than the penetration of the electrolyte into gas diffusion layer. Less