Synthesis and Catalytic Performance of Pd Nanoparticle/Functionalized CNF Composites by a Two-Step Chemical Vapor Deposition of Pd(allyl)(Cp) Precursor

Abstract

Pd nanoparticle/functionalized CNF composites were synthesized by a two-step chemical vapor deposition of Pd(allyl)(Cp) as precursor at atmospheric pressure. Online mass spectrometry was used to measure the gas fragments during the two-step CVD. The functionalized CNFs and the resulting composites were characterized by temperature-programmed desorption mass spectroscopy, inductively coupled plasmaoptical emission spectroscopy, X-ray diffraction, and transmission electron microscopy. The catalytic hydrogenation of cyclooctene on the Pd/CNF nanocomposites was also investigated in a fixed-bed reactor at 40 °C under atmospheric pressure. No palladium deposition was observed on the raw CNFs, as a result of the absence of anchoring sites. The functionalization of CNFs with HNO 3 solution resulted in the formation of surface oxygen groups. The Pd(allyl)(Cp) precursor could be dissociatively adsorbed on the surface of the CNF by the reaction between the ligands and the surface oxygen groups. Further reduction in H 2 formed the Pd/CNF nanocomposites. The palladium loading on the functionalized CNFs depends on the degree of functionalization of the CNFs and on the amount of precursor provided. TEM and XRD results showed that highly dispersed and evenly distributed Pd particles with diameters of 2-4 nm could be prepared by this two-step CVD method. The Pd/CNF nanocomposite catalysts exhibited high activity and stability in the catalytic hydrogenation of cyclooctene, which can be attributed to the special interaction between the palladium nanoparticles and the CNFs and to the mesoporous nature of the CNFs, which prevents mass transfer limitation. The two-step CVD route has great potential in the controlled synthesis of CNF-supported metal catalysts with high dispersion and uniform distribution.

Ozone Sensing Based on Palladium Decorated Carbon Nanotubes

“…In our study, the size of Pd NPs deposited on MWCNTs was about 11 nm in contrast with other studies using the same method of decoration with NPs for CNTs and titania nanotubes, which reported NP diameters about 3.2 and 2.1 nm, respectively [26]. Liang et al [48] deposited Pd NPs on carbon nanofibers (CNFs), obtaining NPs with diameters ranging from 2 to 4 nm. Nanoparticles of noble metals such as Pt, Au and Pd are highly mobile and they migrate to the surface and agglomerate into larger particles due to weak interactions between metal and support [49].…”

Reaction Engineering Strategies for the Production of Inorganic Nanomaterials

“…However, in some cases the surface where the CVD process forms the ENMs is a nanomaterial itself. As an example, carbon nanofibers have been functionalized with Pd nanoparticles that were formed on the nanofiber surface by a CVD process using an organometallic Pd precursor . Nonetheless, the best‐known example of nanomaterials synthesis by CVD corresponds to the production of carbon nanotubes (see for instance the recent review by Nguyen et al) .…”

In situ synthesis of highly-active Pt nanoclusters via thermal decomposition for high-temperature catalytic reactions

“…The TGA data, as shown in Fig. 22 The oxygen groups are also favourable to immobilize the NPs on carbon supports leading to considerably enhanced catalyst activity. The primary weight loss $2.8% is consistent with the weight fraction of the acac ligand in Pt(acac) 2 /CS, which might be ascribed to the catalytically decomposition of Pt(acac) 2 on the surface of carbon spheres.…”