CO2 methanation over supported nickel catalysts attracts an increasing attention. However, the mechanism with it is still in debate. It is confirmed here that the structure of Ni/TiO2 catalyst has a significant effect on CO2 methanation. The catalyst with Ni (111) as the principal exposing facet shows higher activity with higher methane selectivity. The maximum activity for CO2 methanation is obtained at 350 degrees C with a CO2 conversion of 73.2% and a CO2 conversion rate of 1.56 mol(co2)g(cat)(-1)h(-1) at a high GHSV of 60,000 h(-1). This rate is higher than those reported CO2 conversion rates in the literature. According to the FTIR analysis, CO2 methanation over catalyst with Ni (111) as the principal exposing facet follows the mechanism via CO intermediate, while the catalyst with multi-facets takes the pathway of the direct hydrogenation of formate, with which nickel is only functional for hydrogen dissociation.(C) 2016 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.