In the copper–chlorine (Cu–Cl) thermochemical cycle of hydrogen production,a series of chemical reactions are used to decompose water into its constituents (oxygen and hydrogen).Four main chemical reactions are involved in this cycle,in which three aredriven thermally and one electrochemically.Oxygen is produced during one of these chemical reactions.This reaction is an endothermicthermolysisprocess that requires a temperature of 530 ℃ which is the highest temperature in the Cu-Cl cycle.