The low temperature reduction of a NiO catalyst by CH4 was performed in a coaxial double dielectric barrier discharge (DBD) reactor for the first time. The reduction involves active surface carbon which is produced via plasma decomposition of CH4. On the reduced Ni catalyst, activation of CH4 and its fragments to form H-2 and carbon nanofibres occurred at 330 degrees C. CH4 conversions of 37%were achieved in the plasma-catalytic reaction at atmospheric pressure, with 99% selectivity towards H-2 and solid carbon. These results demonstrate a synergistic effect where both the plasma and catalyst are vital for the production of H-2 and carbon nanofibres. In the absence of the catalyst stable plasma could not be ignited with a pure CH4, flow and thermal studies showed that in the absence of the plasma CH4 conversion was minimal. (C) 2011 Elsevier By. All rights reserved.