The DFT calculation of CO hydrogenation was studied based on the reaction of co-adsorbed CO and 2H(2) on beta-Mo2C(100) and Co-Mo carbide slabs. The hydrogenation of CO occurred on the two carbide slabs; undissociative adsorbed CO reacted with three dissociative H's to successively yield CHO, CH2O and CH2OH adsorbed on the beta-Mo2C(1 00) slab, while the fourth hydrogen attack produced the adsorbed CH2 and H2O. On the other hand, the Co-Mo carbide slab produced the adsorbed CH3, O and H through CHO and CH2O but not through CH2OH. CH3OH was not produced on both the beta-Mo2C(100) and Co-Mo carbide slabs, which corresponded to the mass spectroscopic measurement results of no CH3OH formation. Furthermore, electronic structure calculations revealed the CO hydrogenation mechanism. A strong peak of the density of states on the Mo contributes to the CO activation, and the addition of Co increases the number of electrons around this peak position, which improves the CO activation. (C) 2012 Elsevier B.V. All rights reserved.