Progress of international program on hydrogen production with the copper–chlorine cycle

This paper highlights and discusses the recent advances in thermochemical hydrogen production with the copper–chlorine (Cu–Cl) cycle. Extended operation of HCl/CuCl electrolysis is achieved, and its performance assessment is conducted. Advances in the development of improved electrodes are presented for various electrode materials. Experimental studies for a 300 cm2 electrolytic cell show a stable current density and production at 98% of the theoretical hydrogen production rate. Long term testing of the electrolyzer for over 1600 h also shows a stable cell voltage. Different systems to address integration challenges are also examined for the integration of electrolysis/hydrolysis and thermolysis/electrolysis processes. New results from experiments for CuCl–HCl–H2O and CuCl2–HCl–H2O ternary systems are presented along with solubility data for CuCl in HCl–H2O mixtures between 298 and 363 K. A parametric study of multi-generation energy systems incorporating the Cu–Cl cycle is presented with an overall energy efficiency as high as 57% and exergy efficiency of hydrogen production up to 90%. •Recent advances in thermochemical hydrogen production with the Cu–Cl cycle.•Performance of CuCl/HCl electrolytic cell for over 1600 h of operation.•Improved electrodes and results for Silane and 2 Nafion/polypyrrole membranes.•Multi-generation integrated Cu–Cl cycle and improvements of the exergetic efficiency.