A periodic DFT study of CO adsorption over Pd–Cu alloy (111) surfaces

Recently, a catalyst for the conversion of bioethanol to butan-1-ol and hexan-1-ol on the nanoparticles of Pd_xCu_y alloy on the γ-Al₂O₃ support was proposed. The catalyst possesses 90% selectivity and high activity with a conversion rate of 40–45%, together with high stability of operation – 20 cycles of 5-h catalytic runs at 275 ^∘C. The key factor of its stability is the resistance to the CO poisoning. In the present work, we attempted to understand the effect of copper doping on the CO adsorption energy of the bimetal surface using density functional theory. We used the virtual crystal approximation to estimate the influence of the electronic structure of the bimetal as a whole and compared the results with the supercell approach. It was found that the shift of the d band center relative to the Fermi energy does not correlate with a decrease in adsorption energy with the increasing dopant (copper) content. At the same time, the changes in the surface structure and surroundings of the active center do decrease the calculated energy of CO adsorption, and this effect is achieved with a copper content of more than 60% atomic, which coincides with the copper content in the bimetallic particles of the working catalyst.