A highly stable and extremely active nickel (Ni) nanoparticle catalyst, supported on porous gamma-Al2O3 particles, was prepared by atomic layer deposition (ALD). The catalyst was employed to catalyze the reaction of dry reforming of methane (DRM). The catalyst initially gave a low conversion at 850 degrees C, but the conversion increased with an increase in reaction time, and stabilized at 93% (1730 L h(-1) g (-1)(Ni) at 850 degrees C). After regeneration, the catalyst showed a very high methane reforming rate (1840 L h(-1) g (-1)(Ni) at 850 degrees C). The activated catalyst showed exceptionally high catalytic activity and excellent stability of DRM reaction in over 300 h at temperatures that ranged from 700 degrees C to 850 degrees C. The excellent stability of the catalyst resulted from the formation of NiAl2O4 spinel. The high catalytic activity was due to the high dispersion of Ni nanoparticles deposited by ALD and the reduction of NiAl2O4 spinel to Ni during the DRM reaction at 850 degrees C. It was verified that NiAl2O4 can be reduced to Ni in a reductive gas mixture (i.e., carbon monoxide and hydrogen) during the reaction at 850 degrees C, but not by H-2 alone. (C) 2016 Elsevier B.V. All rights reserved.