A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma-catalytic dry reforming of CH4 and CO2 into higher value synthesis gas (syngas). The influence of reaction conditions (e.g. CO2/CH4 molar ratio and total feed flow rate) and supported metal catalysts M/gamma-Al2O3 (M = Ni, Co, Cu and Mn) on the performance of the plasma process has been investigated in terms of the conversion of feed gases, the selectivity and yield of major gas products, and the energy efficiency of the plasma process. The combination of plasma with the Ni/gamma-Al2O3 and Mn/gamma-Al2O3 catalysts significantly enhanced the conversion of CH4 and exhibited a plasma-catalytic synergy for this and the overall energy efficiency of the process. The maximum CH4 conversion of 19.6% was achieved for the plasma-catalytic dry reforming over the Ni/gamma-Al2O3 catalyst at a discharge power of 7.5 W and a gas flow rate of 50 ml min(-1). However, the presence of any of these catalysts in the plasma did not show any synergy for CO2 conversion. In addition, the integration of plasma and the gamma-Al2O3 supported catalysts was found to enhance the yield of CO and H-2, whilst the Ni/gamma-Al2O3 catalyst exhibited the best activity for syngas production. (C) 2015 Elsevier B.V. All rights reserved.