Hydrogen chloride (HCl) by-product is often produced from chlorine-consuming processes. Traditional electrochemical processes for converting HCl to chlorine (Cl-2) are completed by anodic oxidation reaction coupled with cathodic reduction reactions (two major types: hydrogen evolution reaction and oxygen reduction reaction). Herein, a triiodide (I-3(-))/ iodide (I-) redox-mediated cathode is implemented for the first time for converting HCl to Cl-2. The iodide (I-) can be converted back to triiodide (I-3(-)) by air in a reactor external to the eletrolyzer. The desirable redox potential and facile kinetics of I-3(-)/I- offer a substantially lower operational cell voltage, reducing energy consumption by 20%-25% at a typical current density of 4 kA m(-2) and improving the efficiency of Cl-2 recovery.