Insights into the Mechanism of Nitrobenzene Reduction to Aniline by Phosphomolybdic Acid Supported TM₁ Single-Atom Catalysts

Catalytic hydrogenation of nitrobenzene (Ph-NO2) to aniline (Ph-NH2) is a model reaction in the field of catalysis, in which the development of efficient catalysts remains a great challenge due to the lack of strategies to solve activity and selectivity problems. In this work, the mechanism of Ph-NO2 hydrogenation over Pt-1 supported on phosphomolybdic acid (alpha-PMA) was proposed by density functional theory (DFT) calculations. The results show that the dissociation of the first and second N-O bonds is triggered by single H-induced and double H-induced mechanisms, respectively. The limiting potential of the reaction process is -0.19 V, which is the smallest potential in the field of Ph-NO2 reduction reaction to date. In the whole reaction process, the catalytic active site is the Pt atom, and polyoxometalate plays the role of an electronic sponge in the reaction. Additionally, based on experimentally confirmed Pt-1/Na(3)PMA, the reduction capacity of Pd-1/Na(3)PMA toward Ph-NO2 was predicted by DFT calculation. The distinctive adsorption patterns of Ph-NO2 on Pt-1/Na(3)PMA and Pd-1/Na(3)PMA were elucidated using the DOS diagram and fragment molecular orbital analysis. We anticipate that our theoretical calculations can provide novel perspectives for experimental researchers.