Atomic Level Tuning of Anionic [Au3]− Clusters With Pd Dopant for Catalytic Oxidation of NO Utilizing Molecular O2

Abstract

Rising concentrations of nitrogen monoxide (NO) in the atmosphere have posed significant environmental risks. Conversion of NO to NO₂ is a promising oxidation strategy for reducing NO levels. Therefore, in order to comprehend the oxidation mechanism of NO into NO₂ at the molecular level, we employed density functional theory (DFT) with the M06L functional and the def2TZVP basis set. Pristine and doped anionic [Au_nPd_3–n]⁻ (n = 0–3) clusters were chosen, as gas-phase anionic Au clusters serve as ideal models for mimicking gold catalysts due to their electronic structure, which closely resembles that of active supported gold catalysts. We explored the detailed reaction pathways under the Langmuir– Hinshelwood (LH), termolecular Eley–Rideal (TER), and termolecular Langmuir– Hinshelwood (TLH) mechanisms, where two NO molecules are oxidized to two NO₂ molecules using molecular O₂. Our findings indicate that doping Pd onto anionic [Au₃]⁻clusters enhances the adsorption of both NO and O₂. The calculations demonstrate that the Pd site on bimetallic clusters is more preferable for adsorption than that of the Au site. Moreover, the energetic span model reveals that the [Au₂Pd]⁻cluster is the most efficient cluster for converting NO to NO₂ via the L-H mechanism.