Catalytic transfer hydrogenation of nitrobenzene over Ti3C2/Pd nanohybrids boosted by electronic modification and hydrogen evolution inhibition

Abstract

Catalytic transfer hydrogenation (CTH) with formic acid attracts much interest in catalysis, but the sluggish H* production and undesirable H2 evolution reaction (HER) limit its practical applications. Herein we anchored Pd nanoparticles (NPs) on layered Ti3C2 MXene for efficient and selective CTH of nitrobenzene in the presence of formic acid. Some electrons in Pd NPs transferred to Ti3C2 MXene upon formation of Ti3C2/Pd nanohybrids, as confirmed by XPS and DFT simulations. The electron transfer changed Pd valance electron configuration from 4d10 to 4d10-x. Such electron-deficient Pd NPs tuned reaction pathway and promoted formic acid dissociation, both of which favored the production of active H* atoms, i.e., the exact reductant for CTH. Compared with Pd NPs, Ti3C2/Pd showed stronger adsorption of H* and therefore inhibited the occurrence of HER (2H*→H2). Owing to favorable H* production and HER inhibition, Ti3C2/Pd (15 wt% Pd) showed enhanced nitrobenzene CTH performance with turnover frequency of 351.7 h−1 and 99% aniline selectivity, outperforming most of current catalysts. Our work might inspire designing more advanced CTH catalysts by tuning their valance electron configurations with 2D MXene materials.