Gas Phase Electrolysis of Anhydrous HCl for Dry H2 Production

Abstract

Chlorine (Cl2) is an important feedstock used in a variety of industry processes [1]. Hydrogen (H2) and chlorine gas (Cl2) can be produced by the electrochemical oxidation of hydrogen chloride (HCl) anhydrous gas. Previously, a gas phase hydrogen bromine (HBr) electrolyzer showed better performance than aqueous phase due to a significant increase in reactant diffusion rate [2-5]. Furthermore, sulfonated polybenzimidazole (s-PBI) membranes have shown promising performance in this application because they can be operated in strong acid environments and at high temperature [6].The propose of this work was to elucidate the role of the polymer membrane, the efficiency and durability of cathode catalyst (Pt vs IrRuOx), and the optimal operating parameters (temperature, flow rate, and cell potential). We found that the s-PBI gel membrane doped in 50 wt% H2SO4 showed significantly better performance than NafionTM membranes, regardless of their thickness, due to a reduction in membrane resistance and a decrease in chloride ion crossover. We considered as well how crossover of Cl- from anode to cathode can poison the cathode catalyst, affecting the durability of the electrolyzer. We also discuss how the cell temperature and HCl flow rate affect the performance of the electrolyzer, with a focus on reducing the cell potential required to electrolyze HCl by increasing the reaction temperature.