Decoration of Pd Nanoparticles with N and S Doped Carbon Quantum Dots as a Robust Catalyst for the Chemoselective Hydrogenation Reaction

Achieving high selectivity is one of the major challenges for the noble metal catalysts. A strategy of decoration of Pd nanoparticles by N-S doped carbon quantum dots (N,S-CQDs) to regulate selectivity is proposed. Through adjusting the loading amounts of N,S-CQDs, high selectivity toward catalytic hydrogenation reactions can be obtained. N,S-CQDs facilely adhere to the Pd nanoparticle via surface reactions among C-S/C-N species of N,S-CQDs and C-O species of the carbon support under the catalysis of Pd particles. N loss was detected due to the transformation of some C-N species into nitrogen-containing soluble substances or gas. However, S-containing species, specially-SO2/SO3 species, are turned into C-S-C (thiophene-S), leading to a strong coordination between Pd and S. As a result, a N,S-CQDs-Pd interface is fabricated, in which electrons transfer from Pd to S species and the interface of Pd-S plays a major role in hydrogen spillover and generation of dissociated hydrogen with negative charge. Consequently, Pd@N,S-CQDs suppress the hydrodehalogenation and exhibit superior conversion and selectivity (both 100%) for the selective hydrogenation of various halonitrobenzenes. N,S-CQDs as a nonmetallic promoter of metal catalysts provides a promising strategy for the improvement of selectivity.