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

Abstract

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.

Ultrafast synthesis of carbon quantum dots from fenugreek seeds using microwave plasma enhanced decomposition: application of C-QDs to grow fluorescent protein crystals

“…Similarly, with laser ablation, the time required for the C-QDs synthesis is much shorter, i.e., less than 90 s 4 . Nevertheless, some drawback remains for above techniques, such as; low quantum yield, poor crystallinity, short reaction time is only applicable to the synthetic carbon precursors, reaction time is as long as the hydrothermal process and challenges to rapidly convert highly concentrated carbon precursors into C-QDs without any assistance 52 , 64 , 65 .…”

Multifunctional Catalytic Properties of Pd/CNT Catalysts for 4‐Nitrophenol Reduction

“…[58][59][60][61] The Hspillover can contribute to the reactivity through reversibly stored surface H-species that participate to Pd active site regeneration via reverse spillover. [62] Hydrogen spillover has already been reported for noble metal catalysts supported on O-doped, [63] N-doped [64,65] and S-doped [51,66] carbon materials. According to the heteroatom doping, different types of surface groups have been reported to facilitate the H-spillover on Pd catalysts, such as N-quaternary atoms for N-doped materials [65] and quinone groups for O-doped ones.…”

“…Beside metal dispersion, CNT doping can also modify the electronic density on Pd species via charge transfer. The higher binding energy reported for Pd (0) when supported on Odoped, [49] N-doped [50] or S-doped [51] carbon materials can be attributed to the metal-support interaction, suggesting that electrons transfer from Pd NP to the support, leading to electron deficiency on Pd particles. XPS analyses were performed on the four Pd/CNT catalysts to probe the Pd oxidation state and the charge transfer.…”

Preparation of Heteroatom‐Doped Carbon Materials and Applications in Selective Hydrogenation

“…In addition, the generation of Pd 3 P depended on the ratio of Pd/hypophosrous and the calcination temperature. Recently, they [161] decorated Pd nanoparticles over activated carbon with N, S‐doped carbon quantum dots (N, S‐CQDs) and applied in hydrogenation of nitroarenes and relative homologous compounds. The N, S‐CQDs was synthesized through a simple hydrothermal method using citric acid monohydrate as carbon source and L‐cysteine as N, S precursors.…”