Alternatively, an electrochemical process can be used that as a simple modular design and mild operating conditions.  To complete the electrolysis process, anodic regeneration of Cl2 from HCl must be balanced by a cathodic reaction. There are two major types of cathodes used in HCl electrolysis process: the hydrogen evolution cathode (HEC) (Eqn. 1), and the oxygen reduction cathode, also commonly known as the oxygen depolarized cathode (ODC) (Eqn. 2). HEC-based electrolysis can produce H2as a valuable by-product but ODC-based electrolysis offers significantly lower standard cell voltage due to its high redox potential (1.23 V vs. SHE)
HCl → Cl2 + H2 (1)
4HCl → 2Cl2 + 2H2O (2)
Herein, we demonstrate a gaseous HCl electrolyzer with Fe3+/Fe2+ redox-mediated cathode (IRC) for the first time to regenerate Cl2. At the anode, gaseous HCl is oxidized to generate chlorine and protons, at the cathode, Fe3+ is electrochemically reduced to form Fe2+. Subsequently, Fe2+ is chemically oxidized to Fe3+ by oxygen in a reactor external to the electrolytic cell. Regeneration Fe2+ is recycled to the electrolyzer. Due to high standard potential (po, 0.77 VSHE) and fast kinetics (exchange current density, i0, of ~10−2 A/cm2 on glassy carbon, no catalyst was required), IRC offers substantial benefits over alternative commercial HEC and ODC cathodes. Taking advantage of IRC, a much lower cell voltage is achieved: 0.67 V vs. 1.16 V (with ODC) and 1.22 V (HEC) at a typical current density of 4 kA/cm2. Compared to the commercial HEC or ODC-based HCl electrolysis processes, it will save 45–50% of energy consumption approximately. Moreover, without the need for a precious metal cathode catalyst and a costly thick membrane, the captital cost can be reduced by 40%–50% (IRC: $2,640/m2 vs. HEC: $4,339/m2 and ODC: $5,034/m2, estimated with 4 kA/m2and current materials prices).
 J. Perez-Ramirez, C. Mondelli, T. Schmidt, et al, Energy & Environmental Science, 2011, 4, 4786.
 ThyssenKrupp, HCl electrolysis brochure.
 I. G. Martinez, T. Vidaković-Koch, R. Kuwertz, et al, Electrochimica Acta, 2014, 123, 387.
 Y. H. Wen, H. M. Zhang, P. Qian, et al, Electrochimica Acta, 2006, 51, 3769.