DFT and microkinetic study of acetylene transformation on Pd(111), M(111) and PdM(111) surfaces (M = Cu, Ag, Au)

Density functional calculations and microkinetic simulations were performed on the transformation network of acetylene on Pd(111), M(111) and PdM(111) (M = Cu, Ag, Au) surfaces. It is demonstrated that the adsorption energies on alloy surfaces linearly correlate with the values on the pure metal surfaces. A good linear relationship between the co-adsorption energies of initial states and transition states is revealed with which the barriers of most elementary steps in the reaction network were estimated. To shed light on the transformation of acetylene, microkinetic simulations were conducted on the network. The results show that CHCH and H are dominant species on the surfaces and CCH, CCH₂ and CCH₃ are the main intermediates. Analysis indicates that introduction of coinage metals into Pd reduces the activity, but promotes the selectivity by lowering the barrier of CHCH₂ → CH₂CH₂. The present work provides a comprehensive overview of acetylene transformation on palladium, coinage metals and their alloy surfaces. The linear relationship of adsorption energies between the component metal and alloy surfaces and usage of the TSS relationship to evaluate barriers for microkinetic simulations are worthy of being further studied and extended to other systems.