Shield Effect in Palladium@Graphene with Stability in Strong Acid and Sluggish H-Dissociation for Robust Coupling Hydrogenation–Bamberger Rearrangement of Nitrobenzene

Abstract

The inferior stability of noble metal-based thermocatalysts for effective catalytic hydrogenation reaction severely restricts the production of value-added fine chemicals under a strong acid reaction environment. Herein, a shield effect strategy is proposed to establish ultrafine metal NPs with oxidation layers encapsulated in S- and N-doped graphene with stability for robust coupling-efficient catalytic hydrogenation and acid-catalyzed Bamberger rearrangement of nitrobenzene to p-aminophenol. The unconventional structure based on shield effect comprises an oxide layer with dislocation and tensile strain, enabling sluggish dissociation of H2 to H*, coupled with a local electron-enriched S,N-doped graphene shell, restraining the ultrafast hydrogenation rate to form aniline and enhancing the stability of the catalyst. In addition, the experimental characterization and density functional theory simulation further manifest that the oxidizing effect of nitric acid reconstitutes the charge of the graphene shell, rendering it highly specific for phenylhydroxylamine rearrangement to obtain p-aminophenol with high selectivity. The proposed strategy in this work showcases a universal and practicable method for pinpoint modulation of the inherent performance of attainable metal nanoparticles with a programmable graphene shell microenvironment toward highly specific catalysis under the strong acid reaction environment.