Theoretical Insights into Pd-Induced Local Restructuring of CeO2 for Efficient NH3 Oxidation

Abstract

CeO₂ modified with single-atom Pd is a highly effective catalyst for ammonia oxidation. However, the geometric and electronic properties of this catalyst, and its detailed reaction mechanism remain unclear. In this work, we systematically investigate the potential configurations of single-atom Pd-modified CeO₂(111) and CeO₂(110) surfaces, and evaluate their relative stabilities using density functional theory with on-site Coulomb interaction correction (DFT+U). Our calculated results reveal that single-atom Pd-doped CeO₂ exhibits superior stability compared to single Pd atoms supported on CeO₂ surfaces. Under NH₃ oxidation conditions, Pd doping induces local surface reconstruction of CeO₂, leading to the formation of a unique planar PdO₄ unit. Notably, this planar PdO₄ structure promotes the generation of highly reactive two-coordinated oxygen (O_2C) species and enhances the electron storage capacity of both the Pd⁴⁺ site and the Ce 4f states. These improved properties synergistically facilitate the formation of the key *ONH₃ intermediate during NH₃ conversion, and further promote NH₃ oxidation. So, Pd-modified CeO₂ surfaces consistently exhibit outstanding catalytic performance for the oxidation of NH₃. These mechanistic insights provide valuable guidance for the rational design of highly efficient ceria-based catalysts for NH₃ conversion.