Splitting CO2 into CO and pure O-2 at high temperature through solid oxide electrolyzers (SOEs) could provide an efficient way for energy storage and CO2 utilization. Tubular solid oxide electrolysis cells, with yttrium-stabilized-zirconia (YSZ) as electrolyte, strontium-doped lanthanate (LSM) as anode, cermet of Ag-GDC (gadolinium-doped-ceria) as cathode, is fabricated and operated as SOEs for electrolysis of pure CO2. Such an SOE shows a minimum electrolyzing voltage of 0.70 V and a current density of 1359 mA cm(-2) at 2 V. Its CO production rates are 3.1, 6.6 and 10.0 mL min(-1) at electrical currents of 0.5, 1.0 and 1.5 A, respectively, at 800 degrees C. The corresponding Faraday efficiencies are 88.6%, 94.3%, and 95.2%, and the electrical energy conversion efficiencies are 75.4%, 65.2%, and 56.5%, respectively. An SOE with Ag-GDC electrode is steadily operated at 1.59 V for pure CO2 electrolysis at 800. C for 18 h, suggesting that Ag-GDC is a promising cathode material for SOEs of CO2 electrolysis. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.