Electrochemical hydrogen pumping was investigated with a cell consisting of a CsH2PO4/SiP2O7 composite electrolyte at 200 degrees C. When humidified hydrogen was fed to the anode, the evolution rate of hydrogen at the cathode obeyed Faraday's law up to a current density of 1000 mA cm(-2). In this system, the water-gas shift reaction (WGSR) was promoted electrochemically at the anode during polarization with a feed of humidified carbon monoxide. The overpotential was much higher in humidified carbon monoxide than in humidified hydrogen. With the reactor for the catalytic WGSR located upstream of the anode gas, the overpotential significantly depended on the temperature and space velocity of the reactor. The bilayered electrode composed of a Cu spinel oxide and a Pt catalyst exhibited a low overpotential at low current densities due to the formation of hydrogen over the Cu spinel catalyst. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3232302] All rights reserved.