The supported Rh-based catalysts exhibit the excellent catalytic performances for syngas conversion to C-2 species. In this study, all possible elementary steps leading to C-2 species from syngas have been explored to identify the role of support and its surface hydroxyls over Rh/gamma-Al2O3 catalyst; Here, the results are obtained using density functional theory (DFT) method. Two models: Rh4 cluster supported on the dry gamma-Al2O3(110) surface, D(Rh4), and on the hydroxylated gamma-Al2O3(110) surface, H(Rh4), have been used to model Rh/gamma-Al2O3 catalyst. Our results show that CO prefers to be hydrogenated to CHO, subsequently, starting from CHO species, CH and CH2 species are the dominate monomers among CH chi(chi = 1-3) species rather than CH3 and CH3OH on D(Rh4) and H(Rh4) surfaces, suggesting that gamma-Al2O3-supported Rh catalyst exhibits the high selectivity towards CH chi formation compared to the pure Rh catalyst. On the other hand, D(Rh4) is more favorable for C-2 hydrocarbon (C2H2) formation, whereas H(Rh4) surface easily produces C-2 hydrocarbon (C2H2) and C-2 oxygenates (CHCO,CH2CHO), indicating that the surface hydroxyls of support can affect the selectivity of C-2 species over Rh/gamma-Al2O3 catalyst in syngas conversion. Moreover, compared to the pure Rh(111) surface, Rh/gamma-Al2O3 catalyst can achieve the excellent catalytic performances for syngas conversion to C-2 species. (C) 2016 Elsevier B.V. All rights reserved.