The simultaneous removal mechanisms of H2S and Hg-0 on the perfect and oxygen-deficient ZnO (1 010) surfaces are systematically investigated using periodic density functional theory (DFT) calculations. The most stable adsorption modes of Hg and HgS are located. It is determined that Hg is weakly adsorbed on the two ZnO (1 01 0) surface, while HgS is strongly bound to the surface, which implies that the oxidized form of mercury is in favor of removing mercury from coal gas. For the reaction, the dissociation of H2S is occurred firstly, which is almost not affected by the adsorbed Hg atom on the ZnO (1 01 0) surface comparing with that on the clean ZnO (1 01 0) surface. The dissociated S easily captures Hg in gas or adsorbed on the perfect surface leading to the formation of HgS, which shows that the perfect ZnO (1 01 0) surface is efficient to remove H2S and Hg in coal gas simultaneously and H2S is indispensable to remove Hg. However, the activation energies of the formation of HgS on the oxygen-deficient ZnO (1 010) surface are higher than that on the perfect surface. So the removal efficiency of Hg on the oxygen-deficient ZnO (1 010) surface is lower than that on the perfect surface. (C) 2013 Elsevier B.V. All rights reserved.