Calculations based on the first-principles density functional theory (DFT) were performed to study the possible transformation pathways of ethylene on PdAu( 1 0 0) surface to investigate the effect of Au atom alloying with Pd on the formation of CHx (x = 0-2), which may eventually form carbon monomer and lead to the deactivation of catalysts. The energetic properties of reactions including the scission of the C-H, C-C bond and a hydrogen-shift process were determined. The C-H bond scission is confirmed to be prone to happen on the studied surface, while it is difficult for the C-C bond scission to occur due to relatively high barriers, the values of which are as high as 2.72-4.62 eV. The activation barriers for all related reactions except for the dehydrogenation of vinyl, vinylidene and acetenyl demonstrate that it is harder for the conversion of ethylene to occur on PdAu( 1 0 0) surface than on Pd( 1 0 0) surface, especially for the C-C bond scission. All the results indicate that the alloying of Au atom with pure Pd catalyst can prevent the formation of carbon monomer, which may notably affect properties of catalysts. (C) 2015 Elsevier B.V. All rights reserved.