Ni and Ru impregnated carbon nanofibers (CNFs) have been for the first time successfully applied to an Y2O3-stabilized ZrO2 (YSZ) solid electrolyte to form a catalyst-electrode cell. The catalytic and electrocatalytic properties of this composite Ni or Ru CNFs have been investigated in the CO2 hydrogenation reaction under atmospheric pressure and at temperatures 200-440 degrees C. The only products observed are methane and CO under open circuit and electrochemical promotion conditions. Ni based catalyst-electrodes show methane selectivity up to 55% at 300 degrees C, while the Ru based catalyst exhibits selectivity up to 75% at 390 degrees C. Negative applied potential enhances mildly the hydrogenation rate and the selectivity to CH4 in the case of Ni catalyst-electrodes. Ru based catalyst exhibit under negative applied potential an enhanced hydrogenation rate with no further remarkable improvement of methane selectivity. (C) 2011 Elsevier B.V. All rights reserved.