DFT Comparison of N-Nitrosodimethylamine Decomposition Pathways Over Ni and Pd

Recent experimental studies report rapid and efficient reduction of N-nitrosodimethylamine (NDMA) and related aquatic micropollutants mediated by palladium (Pd) and nickel (Ni) surfaces, but differing mechanisms have been reported for the surface reactions. Here, NDMA adsorption and fragmentation on Ni and Pd surfaces has been studied using supercell slab density functional theory (DFT) calculations. NDMA adsorbs in two stable configurations on each surface. Upright binding through the NO fragment is slightly preferred energetically and provides entrance to an exothermic N, O dissociation pathway with moderately high activation barriers. Flat binding through the NNO plane is somewhat less favorable but leads to a facile and exothermic dissociation across the N, N bond. These results suggest that both mechanisms are in competition and may contribute to the observed catalytic reduction of NDMA over these metals in aqueous solution.