We systematically studied the thermochemical behaviors of alkali metals under the carbon dioxide (CO2) atmosphere and first investigated the hydromethanation performance of the alkali metal carbonate@carbon product formed in the reaction of CO(2)with alkali metals. The on-set reaction temperature of alkali metals with CO(2)is at about 466, 584, and 595 degrees C, respectively, following Li < Na < K. The experimental results indicate that COx-free methane can be selectively and efficiently generated by hydrogenation of these carbonate@carbon composites at 450 degrees C without a catalyst. Among these carbonate@carbon composites, the Li2CO3@carbon composite shows superior methanation performance. The selectivity of methanation is near 100%. The yield and content of methane are able to reach 30.3% and 26.6 mol%, respectively. This work provides an alternative method to produce methane, utilizing CO(2)resources.