Incorporation Of Pd Nanoparticles Research Articles

Cooperative Catalytic Alkyne Hydrosilylation by a Porphyrinic Metal-Organic Framework Composite.

Vinylsilanes are valuable building blocks and important structural units in organic chemistry. Herein, catalytic alkyne hydrosilylation was reported to be promoted by a porphyrin metal-organic framework with the incorporation of Pd nanoparticles (Pd@Ir-PCN-222). Catalytic results showed that Pd@Ir-PCN-222 displayed high catalytic efficiency, giving rise to the E isomer vinylsilane with an excellent turnover frequency (TOF) of 2564 h-1. The mechanism studies revealed that the enhancement of the catalytic activity originated from the cooperation between iridium porphyrin and the Pd nanoparticle in confined spaces. The iridium porphyrin was prone to absorb and condense the hydrosilane and alkyne in the inner cavities of Ir-PCN-222, not only accelerating the reaction but also promoting the Pd nanoparticle to activate the Si-H and C≡C bonds of hydrosilane and alkyne, respectively.

Photoelectrochemical water splitting by a novel design of photo-anode: inverse opal-like UiO-66 sensitized by Pd and decorated with S,N graphene QDs

UiO-66 film has been interested for photoelectrodes in water splitting, but it has major problems such as inappropriate band gap and resistant behavior under bias potential. An inverse opal structure was synthesized for the first time and sensitized by plasmonic nanoparticles (Pd) and strategically decorated with S,N graphene quantum dots (S,N GQDs). Consequently, the UiO-66/Pd/S,N GQDs photoanode has indicated a remarkable photocurrent density of ≈300 μA cm−2 at 1.23 V versus RHE under AM 1.5G. Applied bias photon-to-current efficiency (ABPE) is 0.66% at 0.65 V versus RHE and absorbed photon-to-electron conversion efficiency (APCE) is 19.7% under visible light at 500 nm. This high efficiency originated from the engineering of band gap and effective reduction of charge transfer resistance of MOF with the incorporation of Pd nanoparticles. The combination of morphology and composition regulatory of UiO-66 films has key roles in the fabrication of more desirable designing photoelectrodes for photoelectrochemical (PEC) water splitting.

Hydrogen separation using polybenzimidazole membrane with palladium nanoparticles stabilized by polyvinylpyrrolidone

An innovation in hydrogen (H2) selective membrane holds the substantial key of H2 economy. Polymers are the most practical and economical material for membrane fabrication, but their application in H2 separation is always constrained within the selectivity-permeability “trade-off” boundary. The expensive palladium (Pd) thin films offer higher selectivity by facilitating the dissociation, diffusion and re-association of H2 gas. This work reports on the incorporation of Pd nanoparticles into polybenzimidazole (PBI) membranes to surpass the mentioned limitations. Pd nanoparticles were synthesized and stabilized in the inversed microemulsion of polyvinylpyrrolidone (PVP) prior to blending. The X-ray diffraction and energy dispersive X-ray results proved the presence of Pd nanoparticles blended into PBI membrane with dense structure. The agglomerated and the stabilized Pd nanoparticles PBI matrix behaved very differently in H2 adsorption at the rising temperature as shown in temperature-programmed reduction results. The ideal H2/CO2 selectivity of PBI membrane with 1 wt% of Pd nanoparticles was improved by 49% compared to the PBI membrane at 150°C. This membrane surpassed the upper bound Robeson plot at 300°C (ideal H2/CO2 selectivity of 83.57; H2 permeability of 151.73 Barrer) and the H2 permeation could be correlated with Van't Hoff-Arrhenius equation.

Thiol decorated defective metal–organic frameworks embedded with palladium nanoparticles for efficient Cr(vi) reduction

Incorporation of Pd nanoparticles into thiol decorated defective UiO-66 for the reduction of toxic hexavalent chromium Cr(vi) to Cr(iii) in aqueous medium within a very short time under visible light.

Synergetic effect between MoS2 and N, S- doped reduced graphene oxide supported palladium nanoparticles for hydrogen evolution reaction

An active, stable, and relatively low-cost electrocatalyst is crucial in the sustainable production of hydrogen through water electrolysis. In this work, the electrocatalytic activity of Pd supported on MoS2 and nitrogen, sulfur-doped reduced graphene oxide (Pd/MoS2/N,S-rGO) was investigated by two-step hydrothermal method followed by chemical reduction of Pd using sodium borohydride (NaBH4). The Structural and morphological structure of the sample was studied by using X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and high-resolution transmission electron microscope (HRTEM) techniques. The electrochemical hydrogen evolution (HER) performance of the electrocatalyst was studied by using Linear Sweep Voltammetry (LSV), Electrochemical Impedance Spectroscopy (EIS), and Chronoamperometry (CA). The result shows a structural transformation in the MoS2 phase after the incorporation of Pd nanoparticles. The synthesized (Pd/MoS2/N,S-rGO) electrocatalyst shows a significantly lower overpotential of −42 mV vs. RHE at 10 mA/cm2 and Tafel slope value of 38 mV.dec−1. This study demonstrated with low palladium loading, the high activity of the electrocatalyst could have resulted from the cumulative effect of 1T MoS2, sulfur vacancy formation, and higher surface area of N,S-rGO.

Preparation and characterization of highly active Pd nanoparticles supported Mn3O4 catalyst for low-temperature CO oxidation

Two methods were used to prepare Mn3O4 followed by deposition of Pd nanoparticles with 2 and 4 wt.%. The textural and structural properties were characterized by several methods. The XRD results showed the participation of MnO2 phase with small amount with tetragonal Mn3O4 due to hydrothermal treatment at 150 °C. Moreover, no changes in the textural properties of Mn3O4 due to the difference in preparation method or Pd nanoparticles deposition. TEM images showed different morphologies such as cubic, spheroid and plate-shaped structures. The XPS study confirmed the distribution of both Pd° and Pd2+ species on the Mn3O4 surface. The reducibility of pure Mn3O4 was greatly enhanced and shifted to lower temperatures after incorporation of Pd nanoparticles. The presence of Pd2+ may facilitate the providing of reactive lattice oxygen for CO oxidation by the support. The performance of the catalysts towards CO oxidation was much more enhanced as the Pd content increased to 4 wt. %. The results showed good stability and durability during the CO oxidation.

Magnetic covalent hybrid of graphitic carbon nitride and graphene oxide as an efficient catalyst support for immobilization of Pd nanoparticles

For the first time a magnetic carbon based hybrid catalyst, Pd@g-C3N4-Fe-GO, is prepared through covalent conjugation of magnetic graphitic carbon nitride and graphene oxide followed by incorporation of Pd nanoparticles. First, the formation of the catalyst was confirmed via XRD, TG, BET, TEM, FTIR, ICP and VSM analyses and then its catalytic activity for promoting Suzuki and Sonogashira coupling reactions under mild reaction condition was investigated. To elucidate whether hybridization of two carbon materials could improve the catalytic activity, the catalytic activity of the catalyst was compared with the control catalysts (Pd@g-C3N4 -GO, Pd@g-C3N4-Fe, Pd@ Fe-GO, Pd@g-C3N4, Pd@GO and the GO/g-C3N4 physical hybrid). Moreover, the role of magnetic nanoparticles in the catalytic performance was confirmed. Notably, the catalytic activities of the catalyst and the control sample prepared via physical hybridization of two carbon materials were compared to confirm the effect of covalent conjugation on the catalytic activity. Moreover, the study of the substituent effect of p-substituted phenyl iodides was considered by Hammett plot, which revealed a beneficial effect of electron-withdrawing side groups for the CC coupling reaction. Finally, the recyclability of Pd@g-C3N4-Fe-GO as well as leaching of Pd and magnetic nanoparticles was studied.

Selectivity Control in the Tandem Aromatization of Bio-Based Furanics Catalyzed by Solid Acids and Palladium.

Bio‐based furanics can be aromatized efficiently by sequential Diels–Alder (DA) addition and hydrogenation steps followed by tandem catalytic aromatization. With a combination of zeolite H‐Y and Pd/C, the hydrogenated DA adduct of 2‐methylfuran and maleic anhydride can thus be aromatized in the liquid phase and, to a certain extent, decarboxylated to give high yields of the aromatic products 3‐methylphthalic anhydride and o‐ and m‐toluic acid. Here, it is shown that a variation in the acidity and textural properties of the solid acid as well as bifunctionality offers a handle on selectivity toward aromatic products. The zeolite component was found to dominate selectivity. Indeed, a linear correlation is found between 3‐methylphthalic anhydride yield and the product of (strong acid/total acidity) and mesopore volume of H‐Y, highlighting the need for balanced catalyst acidity and porosity. The efficient coupling of the dehydration and dehydrogenation steps by varying the zeolite‐to‐Pd/C ratio allowed the competitive decarboxylation reaction to be effectively suppressed, which led to an improved 3‐methylphthalic anhydride/total aromatics selectivity ratio of 80 % (89 % total aromatics yield). The incorporation of Pd nanoparticles in close proximity to the acid sites in bifunctional Pd/H‐Y catalysts also afforded a flexible means to control aromatic products selectivity, as further demonstrated in the aromatization of hydrogenated DA adducts from other diene/dienophile combinations.

Pd-functionalized MnOx–GeOy nanomembranes as highly efficient cathode materials for Li–O2 batteries

Li–O2 batteries have the potential to be the candidate for the power source to drive electric-vehicles and portable electronics. Recent studies have been focused on searching for stable electrode materials for rechargeable Li–O2 batteries with high efficiency and long cycle life. Here Pd-functionalized MnOx–GeOy nanomembranes were fabricated as the cathode materials of Li–O2 batteries. The incorporation of Pd nanoparticles on the nanomembranes matrix enables the fast transportation of both electrons and lithium ions as well as oxygen-containing species, thus efficiently lowering the charge voltage and greatly prolonging the cycle life of Li–O2 batteries to 160 cycles without apparent degradation. More importantly, Li–O2 batteries using such as-prepared Pd-functionalized MnOx–GeOy nanomembranes can be cycled repeatedly with extremely low charge voltage of only ~3.14V. The presence of small amounts of Pd nanoparticles contributes to the formation of toroid-like Li2O2 during the oxygen reduction reaction which is efficiently decomposed afterwards by the oxygen evolution reaction. The encouraging performance suggests that such nanomembrane-based materials are promising cathode architectures for the future Li–O2 batteries.

Incorporation of Pd Nanoparticles on Rod and Necklace-Like SBA-15 Supports Materials

Ion-exchange of palladium (Pd) precursor for two different types of well-ordered SBA-15 morphologies, necklace-like and rod-like, was studied. Approximately 3.8 wt% Pd was successfully incorporated into SBA-15 at pH 10.3. Formation of SBA-15 and Pd/SBA-15 were characterized by Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM), Thermogravimetry with Simultaneous Difference Thermal Spectroscopy coupled with mass spectrometer (TG/SDTA-MS), Thermogravimetry in combination with Simultaneous Difference Thermal Spectroscopy (TG-SDTA), Inductive Coupled Plasma Mass Spectrometer (ICP-MS) and N2 adsorption-desorption. Reduction of surface area and pore volume of support for Pd/SBA-15 samples may indicate the encapsulation of PdO particles within mesoporous channels of SBA-15.

Pd nanoparticles supported mesoporous γ-Al 2O 3 film as a reusable catalyst for reduction of toxic Cr VI to Cr III in aqueous solution

Pd nanoparticles (NPs) were generated inside the nanocrystalline mesoporous γ-Al 2O 3 films of thickness ∼2 μm. The support γ-Al 2O 3 films were prepared from boehmite sols derived from Al-alkoxide in presence of CTAB. The BET surface area (171 m 2g −1) and pore size (4.3 nm) of the undoped γ-Al 2O 3 films were found to be decreased to 139 m 2g −1 and 3.5 nm respectively after incorporation of Pd NPs. The films were characterized by GIXRD, cross-sectional FESEM, and TEM. TEM/GIXRD confirmed the existence of uniformly dispersed Pd NPs inside the γ-Al 2O 3 films. The Pd NPs (average size ∼4.1 nm)-incorporating mesoporous γ-Al 2O 3 films were used as catalyst to reduce toxic Cr VI compounds to non-toxic Cr III in presence of formic acid as reducing agent at different temperatures (30, 40, 50 and 60 °C). This catalytic reduction process was monitored by UV–visible spectrometer. The rate constant value for the reduction was estimated to be 0.085 min −1 at 50 °C. The same catalytic film can be used for three consecutive cycles by simple washing with water. The catalytic property started to deteriorate after the third cycle. The original catalytic property can be restored fully after heat-treatment of the used films at 300 °C in nitrogen atmosphere.

Incorporation of Pd nanoparticles in mesostructured silica

Monodisperse Pd nanoparticles were prepared by controlled reduction in organic phase and subsequent transfer to aqueous phase. A systematic study was carried out to finely tune nanoparticle size and optimize particle size distribution. The use of 4-dimethylaminopyridine as a transfer agent allowed for the easy and quantitative extraction of the Pd to the aqueous phase. The quaternary amine-functionalized metal nanoparticles were then used as metallic micelle replicas to grow silica around them. This novel and facile metal incorporation method provided an excellent dispersion and homogeneity of Pd nanoparticles on silica supports. In addition, cationic surfactants, such as cetyltrimethylammonium bromide, can be used to produce mesoporosity in these nanoparticles-containing silicas. As an alternative, the metal nanoparticles were functionalized with alkoxysilanes by covalent binding using mercaptopropyltriethoxysilane and then co-polymerized with tetraethoxysilane via basic-catalyzed hydrolysis in the presence of cationic surfactants.