The mechanisms of CHx(x = 1-3) formation from CO hydrogenation on Cu(111) surface have been systematically investigated using periodic density functional calculations. The activation barriers and reaction energies for all the elementary steps involved in CHx(x = 1-3) formation is presented here. CO hydrogenation and its dissociation have been discussed. Our results show that the CO dissociation route is less energetically favored on Cu(1 1 1) surface than CO hydrogenation to form CHO and COH, in which CO mainly goes through hydrogenation to form CHO, meanwhile, the formation of CHO is more favorable both kinetically and thermodynamically than that of COH. Starting from CHO, we further investigate the formation of CHx(x = 1-3), two conditions, without H-assisted and with H-assisted, are considered. As a result, we seek out the optimal paths of CHx(x = 1-3) formation and the corresponding activation barrier of rate-controlled step on Cu(111) surface, moreover, among all CHx(x = 1-3) species, CH2 and CH3 are the most favored monomer for CO hydrogenation on Cu(1 1 1). In addition, our results show that CH3OH is also easily formed by CO hydrogenation, and the formations of CH2, CH3 and CH3OH by CO hydrogenation compete with each other on Cu(1 1 1) surface. (c) 2012 Elsevier B. V. All rights reserved.