Catalytic Activity Of Pd Nanoparticles Research Articles

Enhancing the catalytic activity of Pd nanoparticles in the hydrolysis of ethylenediamine-bisborane through sulfonation of graphene oxide as a solid support

Ethylenediamine-bisborane (EDB), with its high hydrogen storage capacity, has been in the limelight among researchers. In this study, a new catalytic hybrid material (Pd@rGO-SO3H), comprising sulfonated reduced graphene oxide (rGO-SO3H) and palladium (Pd), was developed. This material serves as a highly efficient and reusable catalyst in the hydrogen production from EDB hydrolysis. The synthesized EDB, rGO-SO3H, and Pd@rGO-SO3H were characterized using ICP-OES, PXRD, XPS, SEM, TEM, and TEM/EDX tools. The initial TOF value of the Pd@rGO-SO3H catalyst in hydrogen production from EDB hydrolysis was calculated as 136 min−1. This TOF value was found to be remarkably high compared to related studies in the literature. The reusability performance of Pd@rGO-SO3H was observed to be quite stable. Finally, activation parameters, such as activation energy (Ea), activation enthalpy (ΔH#), and activation entropy (ΔS#) for the hydrolysis reaction, were calculated by conducting catalytic reactions at different temperatures using relevant equations.

Enhanced H2 sensing performance of Pd-modified ZnO nanorods under visible light excitation

High-performance room-temperature hydrogen (H2) sensors are the optimal choice for practical applications. Light excitation, especially visible light, is safer and requires less power compared to ultraviolet (UV) light. This makes it an effective method for achieving room temperature operation. In this study, different mass ratios of Pd-modified ZnO nanorods were synthesized using a combination of hydrothermal and impregnation methods, and their sensing performance to H2 under visible light excitation was investigated. Material characterization results demonstrated that the localized surface plasmon resonance (LSPR) effect of Pd broadened the absorption in the visible light region, increasing the generation of high-energy hot electrons. Notably, the 2.5 wt% Pd/ZnO exhibited excellent sensing performance towards 5000 ppm H2 at room temperature under visible light excitation, with a high response value of 5906.78. The LSPR effect and the catalytic activity of Pd nanoparticles significantly enhance the sensing performance of H2. Based on our current knowledge, there have been no explicit reports on the detection of H2 using visible light excitation with Pd/ZnO, thus highlighting a new direction for the study of room temperature H2 sensors.

Dipolar Microenvironment Enhanced Catalytic Activity of Pd Nanoparticles in MOF Channel

Dipolar Microenvironment Enhanced Catalytic Activity of Pd Nanoparticles in MOF Channel

Gum tragacanth-mediated synthesis of metal nanoparticles, characterization, and their applications as a bactericide, catalyst, antioxidant, and peroxidase mimic

Abstract Among biogenic methods employed for synthesizing various nanoparticles (NPs), gum tragacanth (TGC)-mediated NP production is important. The gum TGC not only qualifies the principles of green chemistry but also embraces unique qualities. In this perspective, the current review concentrates on the composition, uses, and exploitation of gum towards synthesizing metal NP of silver (Ag), gold (Au), palladium (Pd), platinum (Pt), and their characterization (UV-visible absorption spectroscopy, X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy). In addition, applications of synthesized NP as a bactericide, catalyst, antioxidant, and peroxidase mimic are emphasized. Ag NP (13 nm) showed antibacterial action against Gram-negative and Gram-positive bacteria at 2–12 μg‧mL−1. The exploitation of Ag NP as a bactericide makes it a candidate of choice for medicinal and pharmacological applications. The catalytic activity of Pd NP (14 nm) demonstrated borohydride reduction of methylene blue. The gum reduced/capped metal and metal oxide NP serve as redox and photocatalysts for the remediation of toxic pigments and dyes in industrial effluents. At 15 μg‧mL−1, Pd NP exhibited 1,1-diphenyl-2-picrylhydrazyle radical scavenging activity (95.8%) and served as an artificial enzyme mimic for colorimetric sensing of hydrogen peroxide. The industrial applications of other TGC-based nanocomposites, such as heavy metal sorption, wound dressing, drug carrier, tissue engineering, etc., are mentioned.

Synthesis of amorphous trimetallic PdCuNiP nanoparticles for enhanced OER.

Metal phosphides with multi-element components and amorphous structure represent a novel kind of electrocatalysts for promising activity and durability towards the oxygen evolution reaction (OER). In this work, a two-step strategy, including alloying and phosphating processes, is reported to synthesize trimetallic amorphous PdCuNiP phosphide nanoparticles for efficient OER under alkaline conditions. The synergistic effect between Pd, Cu, Ni, and P elements, as well as the amorphous structure of the obtained PdCuNiP phosphide nanoparticles, would boost the intrinsic catalytic activity of Pd nanoparticles towards a wide range of reactions. These obtained trimetallic amorphous PdCuNiP phosphide nanoparticles exhibit long-term stability, nearly a 20-fold increase in mass activity toward OER compared with the initial Pd nanoparticles, and 223mV lower in overpotential at 10mAcm-2. This work not only provides a reliable synthetic strategy for multi-metallic phosphide nanoparticles, but also expands the potential applications of this promising class of multi-metallic amorphous phosphides.

Modulation of two-dimensional palladium nanozyme activity to enhance chemodynamic/photothermal combined therapy for melanoma.

Nanozymes are artificial enzymes that mimic natural enzyme-like activities and exhibit tremendous potential for tumor chemodynamic therapy. However, the development of novel nanozymes with superior catalytic activities for nanotheranostics remains a formidable challenge. Herein, we report a facile synthesis of monodisperse palladium nanosheets (Pd nanosheets) and their assembly on graphene oxide (GO) that enhances the catalytic activities of Pd nanoparticles. Simultaneously, the obtained nanocomposites (rGO-Pd) could be applied as a smart near-infrared (NIR) light-responsive nanotheranostic for near infrared imaging-guided chemodynamic/photothermal combined therapy. Notably, rGO-Pd exhibited high peroxidase mimicking activities, which could catalyze the conversion of intratumoral H2O2 to ˙OH. Impressively, the reactive oxygen species (ROS) generation of rGO-Pd was further remarkably enhanced by the endogenous acidity of the tumor microenvironment and the exogenous NIR light-responsive photothermal effect. These collective properties of the rGO-Pd nanozyme enabled it to be a ROS generation accelerator for photothermally enhanced tumor chemodynamic therapy. Thus, the as-developed rGO-Pd may represent a promising new type of high-performance nanozyme for multifunctional nanotheranostics toward cancer.

Regulating the Catalytic Activity of Pd Nanoparticles by Confinement in Ordered Mesoporous Supports

AbstractStudying structure‐sensitive reactions requires the synthesis of catalytic nanoparticles with precisely controlled sizes. In this work we demonstrate the facile production of size controlled Pd nanoparticles by confinement in the pores of mesoporous silica nanoparticles (MSN). We show that Pd particles 2.1 nm in size have a higher catalytic activity than larger nanoparticles for the Suzuki‐Miyaura cross‐coupling between 4’‐bromoacetophenone and phenyl boronic acid and for the hydrogenation of phenol in aqueous phase. The enhanced activity can be explained in terms of increased number of coordinatively unsaturated sites and higher back donation capacity of the small nanoparticles.

Enhancement of the catalytic activity of Pd nanoparticles in Suzuki coupling by partial functionalization of the reduced graphene oxide support with p-phenylenediamine and benzidine

This paper reports the development of novel supports for highly active Pd nanoparticles for room temperature Suzuki cross coupling reactions. The partial functionalization of the reduced graphene oxide support by the N-containing p-phenylenediamine and benzidine molecules results in the dispersion of small Pd nanoparticles in the solid catalysts Pd/(RGO-PPD) and Pd/(RGO-BZD) which demonstrate excellent catalytic activity for Suzuki coupling under ligand-free ambient conditions with unusual catalytic activity that matches that of the best homogeneous Pd catalysts. They offer remarkable turnover frequencies (400,000 h−1) observed in the microwave-assisted Suzuki cross coupling reaction with easy removal from the reaction mixture, recyclability with no loss of activity, and significantly better performance than most of the reported heterogeneous Pd catalysts. The findings illustrate the exciting opportunities presented by the chemically partially functionalized reduced graphene oxide support for a variety of metallic and bimetallic catalysts for carbon-carbon bond forming reactions.

Synergistic catalysis of Pd–Ni(OH)2 hybrid anchored on porous carbon for hydrogen evolution from the dehydrogenation of formic acid

The development of a facile yet efficient strategy to boost the catalytic performance of supported Pd nanoparticles (NPs) toward the dehydrogenation of formic acid (FA) is essential but remains challenging. Here, a novel hybrid nanocatalyst comprising Pd and Ni(OH)2 supported on porous carbon (PC) is developed. The obtained Pd–Ni(OH)2/PC nanocatalyst exhibits an excellent catalytic performance for FA dehydrogenation to produce hydrogen. The introduction of Ni(OH)2 in PC support can significantly promote the catalytic activity of Pd NPs toward FA dehydrogenation. Additionally, the catalytic property of Pd–Ni(OH)2/PC is correlated with the Pd/Ni ratio. The 2Pd–1Ni(OH)2/PC with the optimum Pd/Ni ratio of 2/1 exhibits the maximum turnover frequency (TOF) of 3409 h−1 at 60 °C for FA dehydrogenation. The highly dispersed ultrafine Pd–Ni(OH)2 hybrid NPs with numerous accessible active sites and Ni(OH)2−induced positive synergetic effects with Pd NPs considerably boost the catalytic performance for FA dehydrogenation.

High Catalytic Activity of Pd Nanoparticles Synthesized from Green Alga Chlorella vulgaris in Buchwald-hartwig Synthesis of N-Aryl Piperazines

Background: The N-aryl piperazines are an important component of many drug products used for the treatment of malaria, depression, anxiety and Parkinson diseases. Buchwald-Hartwig amination is the latest and well-known reaction for Pd catalyzed direct synthesis of N-aryl piperazine from aryl halides. Although several Pd-ligand systems have already been discovered for this conversion, Pd nanoparticles are recently being used for this useful coupling reaction due to their recyclability and durability. Metal nanoparticles show enhanced catalytic activity compared to their bulk counterparts due to increased surface area at the edges and corners. The use of green algal extract in place of chemical ligands makes this process more environment-friendly and cost-effective. In this research, Pd nanoparticles synthesized using green alga C. Vulgaris were utilized as an alternative approach for the coupling reaction during the preparation of N-aryl piperazines. Methods: Synthesized Pd nanoparticles from C. Vulgaris were characterized by FTIR, SEM and XRD techniques. The catalytic activity of the synthesized nanoparticles was monitored for the synthesis of N-aryl piperazines by Buchwald-Hartwig reaction. The synthesized N-aryl piperazines were characterized by NMR, FTIR and mass analysis. Results: A very good catalytic activity of the synthesized Pd nanoparticles from green alga Chlorella vulgaris extract was observed. The green alga not only reduces the size of the Pd metal to nanoparticles but also acts as a green ligand for reduction of Pd(II) to Pd(0) during nanoparticle synthesis. Using this Pd nanoparticles-green ligand system, several N-aryl piperazines were synthesized in good to excellent yields. Reaction conditions for better conversion were optimized. The comparative advantage of the catalytic system with recently published works on Buchwald-Hartwig C-N coupling reaction is given. Recyclability and durability of the catalyst were explored and the results were found to be promising. A plausible mechanism of Pd nanoparticle catalyzed reaction is also proposed. Conclusion: Catalytic activity of the Pd nanoparticle synthesized from Chlorella vulagris in the synthesis of N-aryl piperazines by Buchwald-Hartwig reaction is reported first time to the best of our knowledge and understanding. The green approach of Pd catalyst to facilitate the reaction and its environmental impact is the main characteristic of the process.

Formation of a Pd/MgO Structured Catalyst for the Aqueous Oxidation of Silane to Silanol

The catalytic oxidation of silanes to produce silanols using water as an oxidant at mild temperatures is a major challenge in Si-H activation. Highly efficient and easy-to-recycle catalysts based on Pd nanoparticles are in high demand. In this study, Pd nanoparticles embedded in an MgO porous overlayer on an Mg plate as a structured catalyst was prepared by the plasma electrolyte oxidation (PEO) technique. The Pd/MgO catalyst is strongly anchored to the MgO plate, building a structured catalyst. Fabrication parameters such as the temperature of the electrolyte and applied voltage significantly influenced the structure of the obtained Pd/MgO catalyst and in turn its catalytic activity. The catalytic activities of Pd/MgO were evaluated by activation of a Si-H bond for catalyzing the aqueous oxidation of silanes to silanol at mild temperatures. The catalytic activity of Pd nanoparticles is favored by their electro-deficient state due to influence from the MgO substrate. The Pd/MgO catalyst exhibits good performance stability during recycling. This work paves the way for fabricating structured catalysts with long-term stability and enhanced metal–oxide interaction.

Reducing agent free synthesis of palladium nanoparticles using Schiff base complex and study of its catalytic activity towards reduction of p-nitrophenol to p-aminophenol

A simple and facile synthesis of Palladium nanoparticles (Pd NPs) by solvothermal method using a Schiff base Pd [N,N-bis (5-chloro salicylaldehyde) o-phenylenediamine] complex without use of any reducing agent has been reported here. The as-prepared Pd NPs was further characterized by various techniques such as X-ray Diffraction (XRD), Field Emission Scanning Electron microscopy (FE-SEM), Energy dispersive X-ray (EDAX) and Transmission Electron microscopy (TEM). The catalytic activity of Pd nanoparticles was also performed toward reduction of 4-NP to 4-AP in presence of aqueous solution of NaBH4 at room temperature. This catalyst has excellent catalytic activity for reduction of 4-nitrophenol to 4-aminophenol within 9 min and has excellent reusability for three successive cycles. This enhanced catalytic activity was attributed due to formation of metallic Pd(0) nanoparticles and smaller particle size.

Palladium nanoparticles decorated on a novel polyazomethine as a highly productive and recyclable catalyst for Suzuki coupling reactions and 4-nitrophenol reduction

This report displays the procedure in preparation of fast, highly productive, reusable, and easily retrievable Pd nanoparticles (NPs) as a heterogeneous catalyst (Pd NPs@P(3-MPAP)) immobilized on a novel polyazomethine with phenol group, Poly(3-methyl-4-((pyridin-2-ylmethylene)amino)phenol) (P(3-MPAP)), and the investigation of its catalytic efficiency in fabrication of several biaryl compounds by Suzuki coupling reactions and reduction of 4-nitrophenol to 4-aminophenol. The structures of the synthesized monomer, polymer support material and nanocatalyst were identified by UV–Vis, FT-IR, 1H NMR, TGA, XRD, SEM and EDS methods. The catalytic activity of Pd NPs@P(3-MPAP) catalyst in the synthesis of various biaryls by Suzuki coupling reactions was explored using microwave irradiation, which is rapid, easy, solventless and environmentally friendly method. The nanocatalyst presented outstanding advantageous methodology containing easy work-up with high reaction yield (99%) at very short reaction time (5 min) in solventless media using very low catalyst loading (0.007 mol%) in the synthesis of biaryls. Additionally, the harmful 4-nitrophenol was completely reduced to industrially useful 4-aminophenol in the presence of Pd NPs@P(3-MPAP) with low catalyst amount (1 mg), at very short reaction time (60s) without any toxic solvent (in water) at room temperature. Additionally, reproducibility test results for both catalytic reactions show that the highly productive nanocatalyst was easily retrievable and reusable for six and five sequential cycles, respectively, for Suzuki coupling reactions and reduction of 4-NP without any notable loss in its catalytic activity.

Is the Suzuki-Miyaura Cross-Coupling Reaction in the Presence of Pd Nanoparticles Heterogeneously or Homogeneously Catalyzed? An Interfacial Surface-Enhanced Raman Spectroscopy Study.

Pd-catalyzed Suzuki-Miyaura C-C cross-coupling is very central in chemistry. The question of whether the catalysis by using Pd nanoparticles (NPs) is heterogeneous (on the Pd surface) or homogeneous (by soluble Pd released from the NP surface) remains under fundamental physicochemical debate. This work reports on the in situ characterization of the Suzuki-Miyaura cross-coupling reactions by using surface-enhanced Raman spectroscopy. We find clear evidence of heterogeneous catalysis on the Pd surface. In contrast, the soluble Pd species leaching into the solution cannot catalyze the reaction, indicating a direct contact of the aryl halides with the metal surface is a prerequisite. Accordingly, the surface ligands and charge of the Pd NPs, which determine the molecule-metal contact, are very important in the couplings. By a simple exchange of the surface ligand or a surface modification of the support material, the catalytic activity of Pd NPs is improved due to the enhanced electric attraction between the metal and the reactant molecules.

Pd nanoparticles confined within triazine-based carbon nitride NTs: An efficient catalyst for Knoevenagel condensation-reduction cascade reactions

Pd nanoparticles (NPs) were immobilized within triazine-based g-C3N4 nanotubes (NTs) to obtain a novel bifunctional catalyst, which was used as an efficient catalyst in the Knoevenagel condensation-reduction tandem reaction. The results of Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TGA) demonstrated that Pd NPs were successfully immobilized within triazine-based g-C3N4 NTs. The base amounts of the catalysts were determined by CO2 temperature programmed desorption (CO2-TPD). The textural and morphology of Pd/triazine-based g-C3N4 NTs were characterized by N2 adsorption-desorption, scanning electronic micrograph (SEM), transmission electron microscope (TEM) and CO adsorption. The characterization results indicated that Pd NPs were mainly immobilized on the inner surface of triazine-based g-C3N4 NTs. Pd/triazine-based g-C3N4 NTs showed excellent catalytic performance in the tandem reaction, in which the conversion of benzaldehyde and selectivity to benzylmalononitrile were 100% and 99.2%, respectively. The result was attributed to the high base amounts (especially -NH2 and -NH groups) and the high catalytic activities of Pd NPs within Pd/triazine-based g-C3N4 NTs. Furthermore, the high catalytic activity of Pd/triazine-based g-C3N4 NTs is also attributed to the confinement effect of the nanotube structure. The structure of nanotube not only tune the Pd particle size of the catalysts, but also provide spatial restriction on metal catalyst encapsulated in their channels, which hampered particles aggregation during the reaction, thus maintaining good catalytic activity and stability. Moreover, the anchor and stabilization effects of pyridine N atoms of triazine-based g-C3N4 NTs inhibited the aggregation and the leak of active sites, thereby achieving a good catalytic recyclability with almost unchanged catalytic activity for more than eight times in the tandem reaction.

Dual-reaction triggered sensitivity amplification for ultrasensitive peptide-cleavage based electrochemical detection of matrix metalloproteinase-7

In this work, a new strategy of dual-reaction triggered sensitivity amplification for ultrasensitive electrochemical detection of matrix metalloproteinase-7 (MMP-7) was developed. The sensitivity of amperometric biosensor relies on the current signal differences (ΔI) caused by per unit concentration target. Benefited from dual-reaction catalytic activities of Pd nanoparticles, dual catalytic reactions were implemented in the biosensor to amplify the ΔI: (1) Fenton-like reaction was triggered by the probes to degrade redox species methylene blue; (2) catalytic precipitation reaction was followed subsequently to generate insoluble precipitation by 4-chloro-1-naphthol oxidation. Dual-enhancement of ΔI triggered by Pd nanoparticle-based catalytic probes significantly improved the detection performance of the biosensor. The peptide-cleavage based biosensor integrated Pd nanoparticle-based catalytic probes with reduced graphene oxide-Au/methylene blue-sodium alginate hydrogel (Au-rGO/MB-SA) nanocomposites substrate for ultrasensitive detection of MMP-7. Under optimal conditions, the proposed biosensor exhibited a wide linear range from 10 fg mL−1 to 10 ng mL−1 with an ultralow detection limit of 3.1 fg mL−1. This strategy successfully combines the multiple catalytic reactions triggered by nanomaterials with peptide-cleavage pattern in electrochemical biosensor, providing a promising method for detection of other proteases.

Enhanced H2 gas sensing properties by Pd-loaded urchin-like W18O49 hierarchical nanostructures

Noble metal-semiconductor gas sensors have attached much attention owing to its high sensitivity and excellent selectivity. In this work, non-stoichiometry urchin-like Pd-W18O49 nanostructures are developed for gas sensing applications. Such hierarchical nanostructures were synthesized by two-step approach including a hydrothermal reaction and a subsequent incipient wetness impregnation process. The high sensitivity and excellent selectivity distinguish this sensor from the traditional Pd-WO3 sensor. An insight into the outstanding performance of Pd-W18O49 is provided by contrasting the sensing characteristics of W18O49 and Pd-WO3, which exhibit lower selectivity and response to hydrogen. By comparison, the observed response of Pd-W18O49 sensor is up to 1600– in 0.1 vol% hydrogen at a low working temperature of 100 °C. The excellent and enhanced H2 sensing performances of Pd-W18O49 sensor can be attributed to its novel hierarchical structure, abundant oxygen vacancies, and the catalytic activity of Pd nanoparticles.

Anchoring ultrafine Pd nanoparticles and SnO2 nanoparticles on reduced graphene oxide for high-performance room temperature NO2 sensing

In this paper, we demonstrate room-temperature NO2 gas sensors using Pd nanoparticles (NPs) and SnO2 NPs decorated reduced graphene oxide (Pd-SnO2-RGO) hybrids as sensing materials. It is found that ultrafine Pd NPs and SnO2 NPs with particle sizes of 3–5 nm are attached to RGO nanosheets. Compared to SnO2-RGO hybrids, the sensor based on Pd-SnO2-RGO hybrids exhibited higher sensitivity at room temperature, where the response to 1 ppm NO2 was 3.92 with the response time and recovery time being 13 s and 105 s. Moreover, such sensor exhibited excellent selectivity, and low detection limit (50 ppb). In addition to high transport capability of RGO as well as excellent NO2 adsorption ability derived from ultrafine SnO2 NPs and Pd NPs, the superior sensing performances of the hybrids were attributed to the synergetic effect of Pd NPs, SnO2 NPs and RGO. Particularly, the excellent sensing performances were related to high conductivity and catalytic activity of Pd NPs. Finally, the sensing mechanism for NO2 sensing and the reason for enhanced sensing performances by introduction of Pd NPs are also discussed.

Palladium–cadmium sulfide nanopowder at oil–water interface as an effective catalyst for Suzuki–Miyaura reactions

A simple and effective strategy is described for the synthesis of Pd–CdS nanopowder by the reduction of an organopalladium(II) complex, [PdCl2(cod)] (cod = cis,cis‐1,5‐cyclooctadiene), in the presence of CdS quantum dots (QDs) at a toluene–water interface. We investigated the impact of addition of CdS QDs on catalytic activity of Pd nanoparticles (NPs). The Pd–CdS nanopowder functions as an efficient catalyst for Suzuki–Miyaura reactions for the formation of carbon–carbon bonds. There is a high electron density on Pd NPs and due to their high electron affinity they behave as an electron scavenger from CdS increasing the rate of oxidative addition, which is the rate‐determining step of the catalytic cycle, and, just as we expect, the C─C coupling reaction with the Pd–CdS nanopowder is faster and occurs in less time than that with Pd nanocatalysts. Compared to classical reactions, this method consistently has the advantages of short reaction times, high yields in a green solvent, reusability of the catalyst without considerable loss of catalytic activity and low cost, and is a facile method for the preparation of the catalyst.

Influence of Graphene Oxide Supports on Solution-Phase Catalysis of Thiolate-Protected Palladium Nanoparticles in Water.

The influence of graphene oxide supports and thiolate surface ligands on the catalytic activity of colloidal Pd nanoparticles for alkyne hydrogenation in water is investigated. The studies show that unsupported, water-soluble thiolate-capped Pd nanoparticle catalysts favor the semi-hydrogenation over full-hydrogenation of dimethyl acetylene dicarboxylate (DMAD) under the atmospheric pressure and at room temperature. Pd nanoparticles supported on graphene oxide exhibit a similar activity for the hydrogenation of DMAD, but they show an improved long-term colloidal stability in aqueous solution after multiple catalytic cycles. After the heat treatment of Pd nanoparticles supported on graphene oxide at 300 °C, these heated hybrids exhibit an enhanced catalytic activity towards the full-hydrogenation. Overall, the studies suggest some influences of graphene oxide supports on the stability and thiolate surface ligands on the activity and selectivity of Pd nanoparticle catalysts.