Search

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. Conseq...

A facile synthesis method of palladium phosphide supported on the activated carbon was developed. The effects of Pd precursors for phosphatization, phosphatization temperature, and the ratio of hypophosphite/Pd on the generation of palladium phosphide were investigated, and a generation mechanism of the Pd3P crystal structure is proposed. The results demonstrate that only PdO, rather than Pd or PdCl2, can transform into Pd phosphide without damage to the activated carbon. The penetration of P into the Pd particle can dramatically improve the dispersion of Pd species particles on the activated carbon. The generation of Pd phosphide greatly depends on the phosphatization temperature and the ratio of hypophosphite/Pd. An intact Pd3P crystal structure was obtained when the ratio of hypophosphite/Pd reached 32 and the phosphatization temperature was above 400 &deg, C. The Pd3P supported on the activated carbon exhibited superior catalytic performance in terms of the hydrogenation of halonitrobenzenes to haloanilines because it had few L acids and B acids sites and could not generate deficient-electron active hydrogen atoms as electrophiles.

A nitrogen‐carbon framework with the thickness of several molecules was fabricated through a straightforward nitrogen‐doping strategy, in which specially designed surface‐oxygen‐containing groups (SOGs) first introduced onto the porous carbon support were used to guide the generation of a surface‐nitrogen‐containing structure through condensation reactions between SOGs and the amidogen group of organic amines under hydrothermal conditions. The results indicate that different kinds of SOGs generate different types and abundances of N species. The CO‐releasing groups are apt to form a high proportion of amino groups, whereas the CO2‐releasing groups, especially carboxyl and lactones, are mainly transformed into pyrrolic‐type nitrogen. In the framework with dominant pyrrolic‐type nitrogen, an electron‐rich Pd activated site composed of Pd, pyrrolic‐type N and C is built, in which electron transfer occurs from N to C and Pd atoms. This activated site contributes to the formation of electron‐rich activated hydrogen and desorption of p‐chloroaniline, which work together to achieve the superior selectivity about 99.90 % of p‐chloroaniline and the excellent reusable performance. This strategy not only provides low‐cost, nitrogen‐doped carbon materials, but also develops a new method for the fabrication of different kinds of nitrogen species structures.