Surface restructuring of Cu-based single-atom alloy catalysts under reaction conditions: the essential role of adsorbates.

The stabilities and catalytic performances of single-atom alloy (SAA) structures under the reaction conditions of acetylene hydrogenation are thoroughly examined utilizing density functional theory (DFT) calculations. Four Cu-based alloys with stable SAA structures reported before, namely PdCu, PtCu, RhCu and NiCu alloys, are investigated here. We find that the SAA structures of PdCu and PtCu are stable during the reaction, whilst the RhCu-SAA and NiCu-SAA structures are thermodynamically unstable upon acetylene adsorption and surface restructuring through the aggregation of the Rh and Ni atoms on the surfaces may also happen. It is also found that all the investigated structures of RhCu and NiCu alloys may give rise to the further hydrogenation of ethylene. However, desorption of ethylene is favored over the PdCu-SAA and PtCu-SAA surfaces, indicating that acetylene could be selectively hydrogenated to ethylene over these two surfaces, which is consistent with the experimental observations reported in the literature. Our work provides new understandings regarding SAA surface structures under reaction conditions and their catalytic reaction performances upon aggregation of the doped metal atoms.