Controllable synthesis of oxygenated carbon supported palladium nanodendrites for highly efficient nitroaromatics reduction

Palladium nanodendrites supported on oxygenated carbon layer (Pd/ O-carbon) have been prepared herein through modulating the mass ratio of Pd (II) precursor and carbon dots derived from sucrose without additional reducing agent. Characterizations of FT-IR, XPS spectra and TEM graphs reveal that oxygen-bearing groups on carbon dots play important role in reducing Pd(II) into Pd(0), controlling nanoparticle growth and stabilizing Pd nanodendrites. The as-prepared Pd/ O-carbon presents size-dependent activity on catalytic p-nitrophenol (4-NP) reduction using NaBH4 as hydrogen donor. The reaction rate constant of 4-NP on Pd/ O-carbon with Pd particle size of 4-7 nm almost triples that on catalyst with Pd nanoparticles of 6-10 nm. Pd / O-carbon can be reused for 10 times without obvious decreased activity, showing a long-term chemical stability in 4-NP reduction reaction. In addition, Pd / O-carbon achieves similar to 100% selectivity on nitrobenzene conversion and > 95% selectivity for the hydrogenation of substituted nitrobenzene compounds with methyl-, chloro- and amino- groups to corresponding aniline through tandem reaction with NH3BH3 as hydrogen donor in methanol/ water solvent (volume ratio of 1:3).