Hydrogen is separated from a hydrogen/nitrogen/carbon dioxide mixture by an electrochemical separation method. By applying a direct current to a proton-conducting membrane, hydrogen can be electrochemically dissociated on the platinum catalyst of the anode, transported across the hydrated cation exchange membrane, and then recovered on the catalytic cathode. The operating principles and advantages of the electrochemical hydrogen separation method are described. The effects of temperature and pressure are examined and the optimum operating conditions are determined. Increase in cell temperature enhances the purity of hydrogen and the power efficiency. The pressure of the feeding gas increases both the performance and the amount of hydrogen product, but decreases the purity of the hydrogen because of the increasing permeation flux of impurities, i.e., nitrogen and carbon dioxide. High purity, (99.72%) hydrogen can be achieved from a low purity (30%) feed via a two-stage separation process at 700 mA cm(-2). (C) 2004 Elsevier B.V. All rights reserved.