First-Principles Study of NO Reduction by CO on Cu₂O(110) and Pd₁/Cu₂O(110) Surfaces

Selective catalytic reduction of NO by CO (CO-SCR) is considered as one of the most effective methods for simultaneous removal of two pollutants. The main challenge to achieve this goal is to develop a low-cost, highly effective, and stable catalyst. In this work, on the basis of experimental study, we designed a Pd₁/Cu₂O­(110) single-atom catalyst to improve the selectivity of Cu₂O to N₂. The reaction mechanisms of NO reduction by CO on the undoped Cu₂O­(110) and Pd₁/Cu₂O­(110) were studied by using density functional theory and microkinetic models, and the catalytic performance of the two catalysts was compared. The results showed that both surfaces have high CO oxidation activity. Pd doping improves the adsorption strength of NO and CO and changes the preferential configuration of NO on the surface with oxygen vacancies. Possible reaction pathways for the formation of N₂ and N₂O were located. Microkinetic analysis showed that the overall NO conversion rate and CO₂ formation rate on Pd₁/Cu₂O­(110) are much higher than those on Cu₂O­(110). Compared with the 100% selectivity of N₂O on Cu₂O­(110) at 300–450 K, doping a single Pd atom into the top layer of Cu₂O­(110) can obtain 100% N₂ selectivity in the whole temperature of 300–1000 K. It is further confirmed that the reaction proceeds via the different mechanism on the undoped and Pd-doped surfaces. N₂O is formed on Cu₂O­(110) via the intermediate NNO, while N₂ is formed on Pd₁/Cu₂O­(110) via the dimer ONNO. This study is expected to provide a clue for the design of oxide-supported single-atom catalysts for NO reduction.