NOVELTY - The electrochemical cell comprises an anode compartment comprising an anode for disposition in an anolyte, where the anolyte is cuprous chloride in hydrochloric acid, a cathode compartment comprising a cathode, where the cathode comprises an electrocatalyst, a set of ion exchange membranes arranged between the anode compartment and the cathode compartment, and a center compartment (10) that is defined by the set of ion exchange membranes and comprises an element for removal or sequestering of copper ions that cross one of the membranes from the anode compartment.    USE - The electrochemical cell is useful for producing hydrogen gas and cupric chloride (claimed) using copper chloride/hydrochloric acid electrolysis.    ADVANTAGE - The system removes the copper ions crossing the first ion exchange membrane from the anode compartment by continuously flushing the center compartment with the electrolyte containing a minimum copper ion concentration thus reducing the amount of copper species reaching the cathode and maintaining electrolysis efficiency and high performance of the cell over long periods so as to economically produce hydrogen.    DETAILED DESCRIPTION - The electrochemical cell comprises an anode compartment comprising an anode for disposition in an anolyte, where the anolyte is cuprous chloride in hydrochloric acid, a cathode compartment comprising a cathode, where the cathode comprises an electrocatalyst, a set of ion exchange membranes arranged between the anode compartment and the cathode compartment, and a center compartment (10) that is defined by the set of ion exchange membranes and comprises an element for removal or sequestering of copper ions that cross one of the membranes from the anode compartment. The set of ion exchange membranes comprise anion exchange membranes (5a) and/or cation exchange membranes (5b). The center compartment comprises gas diffusion layers positioned adjacent the ion exchange membranes of the center compartment, and an inlet and an outlet to allow flow of an electrolyte through the center compartment. The inlet and the outlet are connected to an electrolyte source to allow continuous flushing of the center compartment with an electrolyte effective to remove copper ions. The electrolyte further comprises a material that absorbs, adsorbs or reacts with the copper ions in the center compartment. The center compartment is filled with a material to remove the copper ions in the center compartment by adsorption, chelation or other chemical reaction. The center compartment is filled with reticulated vitrious carbon. Copper species are removed from the center compartment in-situ by a deposition, absorption and/or chemical reaction, or ex-situ by a chemical separation process. The set of ion exchange membranes is an ion exchange membrane consisting of actively cooled membrane, AMV, anodic stripping voltammetry, AXE or another anion exchange membranes used for desalination or electrodeionization. The hydrochloric acid concentration in the anolyte is 11 M. The cathode is disposed in a catholyte. The hydrochloric acid concentration in the catholyte is 10 M. The electrocatalyst comprises a thin film coating and is dispersed on a high surface area carbon powder. An INDEPENDENT CLAIM is included for a method for producing hydrogen gas.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic sectional view of a double membrane electrolysis cell in a wide gap configuration.    Anion exchange membrane (5a)    Cation exchange membrane (5b)    Cathode side solution outlet port (8')    Anode side solution outlet port (9')    Center compartment. (10)