CO2 methanation over sponge Ni was investigated. When CO2 methanation was carried out using sponge Ni without any pretreatment, the sponge Ni exhibited a CO2 conversion of 83% at 250 degrees C under a high space velocity (0.11 mol(CO2) g(cat)(-1) h(-1)). We think that the sponge Ni is a promising new catalyst for CO2 methanation because it showed the high activity even under the high GHSV, and we can design a small plug flow reactor compared to a conventional reactor, resulting in a low manufacturing cost for the reactor. The high activity can be derived from the great number of crystal defects of fcc-Ni in the sponge Ni. On the other hand, with high-temperature pretreatment, the sponge Ni lost its activity in CO2 methanation as well as the surface defect sites. Thus, the activity loss can be explained by the disappearance of the surface defect sites by the high-temperature pretreatment. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.