Theoretical study on nitrobenzene hydrogenation to aniline catalyzed by M1/CeO2−x(111) single-atom catalysts

The hydrogenation of nitrobenzene to aniline is a critical process in the production of numerous chemical intermediates and pharmaceuticals. Developing efficient catalysts for this reaction is essential to improve reaction rates and selectivity. A density functional theory (DFT) study was performed to investigate the catalytic activity of twelve late transition metal-doped ceria (M₁/CeO_2-x(111)) single-atom catalysts for the hydrogenation of nitrobenzene to aniline. Firstly, the stabilities and oxidation states of doped metal atoms on M₁/CeO_2-x(111) surfaces were studied. Subsequently, the reactivity of two possible rate-determining steps on M₁/CeO_2-x(111) surfaces, H₂ dissociation and the fourth hydrogen transfer step in the direct route of nitrobenzene hydrogenation (PhNHO* + H* → PhNHOH*), was further investigated. The Brønsted-Evans-Polanyi (BEP) relationship between reaction energies (ΔE) and activation energies (E_a) and the volcano plot between the energies of PhNHOH* (E_PhNHOH*) and the activation energies (E_a) of the fourth hydrogen transfer step were identified. The calculated results indicate that the fourth hydrogen transfer step is the rate-determining step in the overall reaction, and that the Ru₁/CeO_2-x(111) single-atom catalyst could be one of the most promising catalysts with good catalytic activity for the nitrobenzene hydrogenation.