Electrolysis of HCl exhibits promise for large-scale production of hydrogen with the additional benefit of converting a low-value byproduct (HCl) into a more valuable feedstock (Cl₂). However, most of the available publications in literature use aqueous phase HCl as the electrolyte [1-3]. Previously, gas phase hydrogen bromide (HBr) was shown to electrolyze at current densities an order of magnitude greater than that of aqueous HBr [4]. Aqueous HBr electrolysis was limited by slow diffusion in the liquid phase. We show here that gas phase HCl also exhibits higher reactions rates, as reflected by higher current densities, when compared to aqueous phase.

The purpose of this work was to study the efficiency and durability of the anode catalyst (RuO₂ and IrRuO₂), the role of the polymer membrane (Nafion vs. polybenzimidazole), and the operating parameters (temperature, HCl flow rate, and current density) in a proton exchange membrane (PEM) electrolyzer. We found that crossing over of chorine from anode to cathode can poison the catalyst at the cathode, resulting in less durability and shorter lifetime of the electrolyzer. We also discuss how operating temperature, HCl flow rate, and hydration affect the performance of the electrolyzer.

References:

1. Huskinson, J. Rugolo, S.K. Mondal, M.J. Aziz, Energy & Environmental Science. 5 (2012) 8690.
2. Mohammadi , S.N. Ashrafizadehb, A. Sattari, Chemical Engineering Journal 155 (2009) 757–762.
3. Barmashenko and J. Jo"Rissen, Journal of Applied Electrochemistry 35 (2005) 1311–1319
4. Sivasubramanian, R.P. Ramasamya, F.J. Freireb, C.E. Hollanda, J.W. Weidner, International Journal of Hydrogen Energy 32(4) (2007) 463-468.