Graphene/pyrrolic-structured nitrogen-doped CNT nanocomposite supports for Pd-catalysed Heck coupling and chemoselective hydrogenation of nitroarenes

Abstract

This work focused on the synthesis of 3D Pd-based nanocomposites which were tested in Heck coupling reactions and for the hydrogenation of nitroarenes. This was achieved by fabrication of graphene oxide/nitrogen-doped carbon nanotubes (G/N-CNTs) by mechanical grinding of 2D graphene oxide (GO) and 1D oxygen-treated nitrogen-doped CNTs (N-CNTs-OT) in a 3:1 ratio, respectively. The fabrication of G/N-CNTs is to overcome the habitual aggregation and restacking of graphene sheets. Palladium nanoparticles (Pd NPs) were deposited on the 3D G/N-CNTs nanocomposites via metal organic chemical vapour deposition method. The 3D Pd-based nanocomposites were characterized by TEM, SEM, HRTEM, XRD, TGA, XPS, ICP-OES, elemental analysis, BET analysis and Raman spectroscopy. For the Heck coupling reactions, aryl halides, olefins and 3D Pd-based nanocomposites were mixed in a suitable solvent and the reaction carried under microwave irradiation. The chemoselective hydrogenation of nitroarenes was done with dry ethanol in a Paar reactor, purged with H 2 gas. These catalysts demonstrate excellent activity and selectivity in both reactions. The remarkable activity of the 3D Pd-based nanocomposites in Heck reactions and hydrogenation of nitroarenes may be attributed to the small particle size (3-10 nm) and a high degree of dispersion of Pd NPs.

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

“…[11] Among the different catalytic systems used for 4-NP reduction, Pd/C catalysts are particularly attractive since they combine several advantages for 4-NP removal: i) the use of Pd, a metal particularly active for this reaction, [8] as well as for the hydrolysis reaction that NaBH 4 undergoes to release hydrogen; [12] ii) the possibility of 4-NP adsorption on carbon surface; [2] and iii) the use of a support, which if conveniently doped with specific heteroatoms (N, S, P), can also be active for the reaction (Table S1). [13][14][15][16][17][18][19][20][21] Palladium catalysts supported on carbon nanotubes (CNTs) have been the subjects of several studies (Table S2), [22][23][24][25][26][27][28][29][30][31][32][33][34] since this support offers several advantages for catalytic studies, such as: i) flexibility of modulating the specific surface area, chemical composition (doping) and/or surface functionalization; and ii) possibility of tuning metalsupport interactions. [35] Different types of CNTs (doped or not), alone or in combination with another carbon materials have been investigated either as catalysts or catalyst supports for palladium nanoparticles (Pd NP ).…”

Different strategies to simultaneously N-doping and reduce graphene oxide for electrocatalytic applications

“…On the other hand, for all rGO samples, their zeta potential become more negative with increasing pH but, magnitude of zeta potentials are lower than that of GO at the same pH (until pH=7-8) as a consequence of the removal of the oxygen containing functional groups (lower concentration of the ionized groups). The point of zero charge (pHpzc) of rGO-PPy700 and rGO-PPy450 takes place at pH of 3.8 and 4.3, respectively and at pH of 7.1 for sample HT-rGO which revealed a significant modification of the surface charge behavior with an increase of the surface basicity (as a function of the pH value) after oxygen functionalities reduction [42,43,44]. The higher pHpzc of HT-rGO compared to rGO-PPy samples, may be due to its restack into a much more ordered crystalline structure.…”