Low-voltage gaseous HCl electrolysis with an iron redox-mediated cathode for chlorine regeneration

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Zhao, Yun
Gu, Shuang
Gong, Ke
Zheng, Jie
Wang, Junhua
Yan, Yushan

Y. Zhao, S. Gu, K. Gong, J. Zheng, J. Wang, Y. Yan, Angew. Chem. Int. Ed. 2017, 56, 10735


Gaseous HCl as a by-product is often produced from chlorination processes using Cl-2 gas. Onsite Cl-2 regeneration from HCl is highly desirable as it eliminates the need to buy new Cl-2 and dispose HCl waste. A gaseous HCl electrolysis with Fe3+/Fe2+ redox-mediated cathode is demonstrated for Cl-2 regeneration. HCl is oxidized to generate Cl-2 and protons in the anode while Fe3+ is reduced to Fe2+ in the cathode. Simultaneously Fe3+ is regenerated by chemical oxidation of Fe2+ by oxygen (air) that also produces water. A low operational voltage and high coulombic efficiency are achieved by using a novel composite porous membrane and hydrophobic anode. Specifically, a cell voltage of only 0.64 Vis needed at the typical current density of 4 kA m(-2), leading to a low energy consumption of 483 kWh per ton of Cl-2 (124 kJ mol(Cl2)(-1)) which is about 50-55% of state-of-the-art HCl electrolysis processes.

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