Superior suppression hydrodehalogenation performance of Pd nanoparticle decorated with metalloid-promoter GQDs for the selective hydrogenation of halonitrobenzenes

A novel Pd nanocomposites (Pd@GQDs) tightly surrounded by GQDs on the porous carbon sphere is fabricated for the application in the thermocatalytic fields. The samples were characterized by BET, UV–Vis, PL, XRD and TEM and evaluated on their catalytic selective hydrogenation performance. The results show that strong surface interaction between abundant surface groups of GQDs, especially –COO−1 group, and Pd particle induces and drives GQDs directional deposition around the Pd particle in the process of Pd@GQDs generation. In the Pd@GQDs cluster, the electron distribution of Pd particle is rearranged and Pd possesses electron-rich property. The metalloid-promoter GQDs act as an electron donor like various metal additives in multicomponent metal catalysts in the thermocatalytic fields. The Pd@GQDs generates electron-rich H other than electron-deficient H when hydrogen is adsorbed on it, which might prefer to attack nitro group in halonitrobenzene molecule, compared with C–X bond. The superior selectivity and stability for the hydrogenation of various halonitrobenzenes to corresponding haloanilines are obtained. GQDs demonstrate a great prospect of application as a nonmetallic electron promoter in thermocatalytic fields.