Pd Nanoparticles Research Articles

Pyridine N-induced intra-pore and interfacial dual-confined Pd0-Pdδ+ synergistic catalysis for ultra-stable dehydrogenation of dodecahydro-N-propylcarbazole

We developed nano Pd catalysts, encapsulated within carbon-nitrogen layers at both intra-pore and interfacial levels on SiO2, via in-situ thermolysis of metal-organic coordination compounds. The catalysts dehydrogenation efficacy is greatly influenced by thermolysis temperature and ligand-to-metal ratio. The Pd-C-N2/SiO2-600 catalyst notably achieved complete dehydrogenation of 12 H-NPCZ within 240 minutes, demonstrating exceptional stability over 10 cycles without significant degradation, highlighting its viability for commercial use. Characterizations revealed that the C-N layer integration improves Pd nanoparticle dispersion and reduces strong acid site formation on catalyst surface. This synergy between the C-N layer and Pd nanoparticles promotes the formation and stabilization of Pdδ+ species, optimizing them as adsorption sites for dehydrogenation with appropriate acid strength. Moreover, this interaction adjusts the electronic states of Pd0 active sites, optimizing adsorption dynamics for intermediates. This cooperative action between Pd0 and Pdδ+ significantly boosts the desorption rate of dehydrogenation products, substantially improving the catalysis performance.

Single Atom Catalysts Remodel Tumor Microenvironment for Augmented Sonodynamic Immunotherapy.

The immunosuppressive tumor microenvironment (TME) is a huge hurdle in immunotherapy. Sono-immunotherapy is a new treatment modality that can reverse immunosuppressive TME, but the sonodynamic effects are compromised by overexpressed glutathione (GSH) and hypoxia in the TME. Herein, this work reports a new sono-immunotherapy strategy using Pdδ+ single atom catalysts to enhance positive sonodynamic responses to the immunosuppressive and sono-suppressive TME. To demonstrate this technique, this work employs rich and reductive Ti vacancies in Ti3-xC2Ty nanosheets to construct the atomically dispersed Pd-C3 single atom catalysts (SAC) with Pd content up to 2.5 wt% (PdSA/Ti3-xC2Ty). Compared with Pd nanoparticle loaded Ti3-xC2Ty, PdSA/Ti3-xC2Ty single-atom enzyme showed augmented sonodynamic effects that are ascribed to SAC facilitated electron-hole separation, rapid depletion of overexpressed GSH by ultrasound (US) excited holes, and catalytic decomposition of endogenous H2O2 for relieving hypoxia. Importantly, the sono-immunotherapy strategy can boost abscopal antitumor immune responses by driving maturation of dendritic cells and polarization of tumor-associated macrophages into the antitumoral M1 phenotype. Bilateral tumor models demonstrate the complete eradication of localized tumors and enhance metastatic regression. Th strategy highlights the potential of single-atom catalysts for robust sono-immunotherapy by remodeling the tumor microenvironment.

A Palladium Catalyst Supported on Boron-Doped Porous Carbon for Efficient Dehydrogenation of Formic Acid.

Formic acid has emerged as a highly promising hydrogen storage material, and the development of efficient catalysts to facilitate its dehydrogenation remains imperative. In this study, a novel catalyst consisting of palladium nanoparticles supported on boron-doped porous carbon (Pd/BPC) was successfully synthesized to enable efficient hydrogen production through the dehydrogenation of formic acid. The impacts of the boron doping ratio, doping temperature, and palladium reduction temperature on the catalyst's performance were systemically investigated. The results demonstrated the Pd/BPC catalyst synthesized with a carbon-to-boron ratio of 1:5 by calcination at 900 °C and subsequent reduction at 60 °C exhibited superior formic acid dehydrogenation performance, being 2.9 and 3.8 times greater than that of the Pd/PC catalysts without boron doping and commercial Pd/C, respectively. Additionally, the catalyst showed excellent cycle stability with no significant activity reduction after five consecutive cycles. Experimental and theoretical results reveal that boron doping not only facilitates the homogenous distribution of Pd nanoparticles but also induces a stronger support-metal interaction, thereby reinforcing the catalytic performance. This research is expected to provide valuable insights into the economically viable and efficient production of environmentally friendly hydrogen energy.

Highly active Pd nanoparticles decorated on benzene‐ring doped g‐C3N4 as catalyst in methylene Blue degradation and Cr (VI) ions reduction

The development of simply prepared, highly active and reusable nanocatalysts for methylene blue degradation (MB) or Cr (VI) ions reduction under sunlight conditions in wastewater remains a challenge in the field of green chemistry. Addressed herein is the catalyst of Pd(0) nanoparticles supported on benzene ring doped graphitic carbon nitride (Pd@BD‐g‐C3N4) for MB degradation or Cr (VI) ions reduction under visible light irradiation. Pd@BD‐g‐C3N4 nanocatalyst has been synthesized using the facile wet impregnation–chemical reduction method to boost the catalytic efficiency of BD‐g‐C3N4. The MB degradation or Cr (VI) ions reduction proceeded efficiently in the presence of Pd@BD‐g‐C3N4. Compared with pure BD‐g‐C3N4 in both studies, the hybrid photocatalyst Pd@BD‐g‐C3N4‐exhibited enhanced visible light photoactivity was higher than of pure BD‐g‐C3N4. In addition, in the reusability tests, it was observed that the Pd@BD‐g‐C3N4 photocatalyst has good stability and repeated cycle performance. The electronic and morphologic structure of support material and nanocatalyst were characterized by several techniques such as FT‐IR, DR/UV‐Vis, BET, SEM‐EDX, HR‐TEM, P‐XRD, and XPS analyses.

Highly active polyethylene glycol grafted cellulose supported Pd nanoparticles for glucose electrooxidation

In this study, poly(ethylene glycol) (PEG) grafted cellulose (CE) composite catalyst support material (PEG-CE) was obtained by chemically cross-linking PEG at varying molecular weight and CE with isophorone diisocyanate (IPDI) and 2,4-toluylene diisocyanate (TDI). PEG-CE supported Pd (Pd/PEG-CE) catalyst was prepared by the chemical reduction method. The crystal size of the Pd/PEG-CE catalyst is 4.79 nm and its crystal structure has been determined to be face-centered cubic Pd. Elemental mapping results indicate that Pd was reduced onto PEG-CE successfully and uniformly. Pd exists in the elemental and Pd-O form in the catalyst system. The Pd loading rate of Pd/PEG-C_IPDI catalyst was determined as 18.8% by mass. Among the PEG-CEs prepared with TDI and IPDI, PEG4000-CE_TDI and PEG6000-CE_IPDI displayed the highest specific activities of 1.03 and 1.50 mA cm−2 for glucose electrooxidation. With Pd reduction on PEG4000-CE_TDI and PEG6000-CE_IPDI, the specific activities increased to 1.62 mA cm−2 and 6.97 mA cm‐2. Pd/PEG6000-CE_IPDI has the highest electrocatalytic activity and stability in this study for glucose electrooxidation and is an encouraging anode catalyst for direct glucose fuel cells.

Comparison of Pd Nanoparticle-Decorated Softwood and Hardwood Activated Carbon in Catalytic Reduction of High-Concentrated Industrial 4-Nitrophenol

Carbon-based catalyst from natural wood recently shows a great potential in environmental remediation due to its naturally hierarchical and anisotropic porous structure. However, few studies have focused on the difference in structure-property-function between the two categories of hardwood and softwood. Herein, Pd nanoparticles decorated softwood (Pd/SAC) and hardwood activated carbon (Pd/HAC) were fabricated for catalytic reduction of high-concentrated 4-nitrophenol (4-NP, 2.0 g L−1). The results show that the developed Pd/HAC has larger specific surface area (474 m2 g−1), more abundant pits and nanopores than Pd/SAC (412 m2 g−1), offering Pd/HAC with abundant interpenetrating channels for efficient mass transfer. As a result, Pd/HAC demonstrates outstanding performance in catalytic reduction of 4-NP, with the turnover frequency value up to 1.25 mol4-NP mol−1 min−1, much higher than Pd/SAC (0.92 mol4-NP mol−1 min−1), even at lower Pd nanoparticles loading (0.551 % vs. 0.573 %). The mesopores/micropores ratio of wood-based activated carbon is considered to be an important parameter affecting the mass transfer process. Pd/HAC also demonstrates superior catalytic stability and reusability, with the shedding degree of decorated Pd nanoparticles much lower than Pd/SAC when subjected to 9 cycles. Hardwood is demonstrated to be a promising activated carbon precursor, and exhibits unique hierarchical porous structure that can highly promotes the catalytic performance in industrial wastewater treatment.

Modulating the d-Band Center of Palladium via Ethylene Glycol Modification: Accelerating Had Desorption for Enhanced Formate Electrooxidation.

This study addresses the critical challenge in alkaline direct formate fuel cells (DFFCs) of slow formate oxidation reaction (FOR) kinetics as a result of strong hydrogen intermediate (Had) adsorption on Pd catalysts. We developed WO3-supported Pd nanoparticles (EG-Pd/WO3) via an organic reduction method using ethylene glycol (EG), aiming to modulate the d-band center of Pd and alter Had adsorption dynamics. Cyclic voltammetry demonstrated significantly improved Had desorption kinetics in EG-Pd/WO3 catalysts. Density functional theory (DFT) calculations revealed that the presence of EG reduces the d-band center of Pd, leading to weaker Pd-H bonds and enhanced Had desorption during the FOR. This research provides a new approach to optimize catalyst efficiency in DFFCs, highlighting the potential for more effective and sustainable energy solutions through advanced material engineering.

GrafeoPlad Palladium: Insight on Structure and Activity of a New Catalyst Series of Broad Scope

AbstractGrafeoPlad‐Pd, a new metal‐organic alloy comprised of Pd nanoparticles doped with 3D‐entrapped graphene oxide, has promising applicative potential in sustainable synthetic organic chemistry. Besides hydrogenation, the metal nanopowder comprising the material is also active and relatively stable in cross‐coupling reactions carried out consecutively. X‐ray photoelectron spectroscopy (XPS) surface investigation and density functional theory (DFT) calculations are applied to gain new insight into the structure and potential new catalytic activity of this new class of molecularly doped metals.

The Effect of Reduction Pretreatments on the Size of Supported Pt and Pd Nanoparticles Prepared by Strong Electrostatic Adsorption

Supported catalyst synthesis involves pretreatment (drying, reduction) of metal complexes to form metal nanoparticles. This study has been undertaken to explore the effect of reduction temperature, heating rate, and water partial pressure on final particle size of Pt and Pd supported on a total of four carbon and oxide supports. Supported nanoparticles were synthesized by strong electrostatic adsorption (SEA) and dry impregnation (DI); the former method was hypothesized to yield greater nanoparticle stability in thermochemical reducing environments stemming from the strong interaction of the precursor with the support during impregnation. Reduced samples were characterized by in-situ and ex-situ XRD and STEM. The DI-derived samples generally showed an expected increase of particle size with increased reduction temperature, and severe particle coalescence in humid hydrogen, while the SEA-derived samples did not sinter at the elevated reduction temperatures (up to 500 °C) and were remarkably stable in the humid reducing environment.Graphical

Reaction-induced restructuring of partial Pd single atoms to nanoparticles for enhancing HMF selective hydrogenation to BHMTHF

Selective reduction of 5-hydroxymethylfurfural (HMF) to valuable 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) remains a significant challenge under mild conditions. The synergistic effect between metal single atoms (SAs) and nanoparticles (NPs) can greatly enhance catalytic activity. Here, a high-performance Pd SAs catalyst supported on N-doped carbon (PdSAs/NC) was developed from Pd@UiO-66-NH2. It was found that partial Pd SAs were spontaneously restructured into Pd NPs during the reaction. Our catalyst exhibited 100% conversion of HMF and 98% selectivity towards BHMTHF at temperature as low as 0 °C. In situ FTIR spectra results and density functional theory calculations indicate that Pd SAs contribute to the C = O activation, while Pd NPs facilitated the H2 dissociation into H* atoms, resulting in synergistic catalytic activity between Pd SAs and Pd NPs.

Palladium nanoparticles (Pd NPs) immobilized over polydopamine-functionalized Zn-Al mixed metal oxide as a novel nanocatalyst for synthesis of C-C bond via Suzuki-Miyaura coupling reactions

In recent times modified hydrotalcite like compounds formed with metal oxide layers has gained considerable importance as improved nanoparticle (NP) supports along with their unique electronic properties that inherently stabilizes the immobilized NPs. The present work demonstrates an adapted protocol towards the Pd NPs immobilized polydopamine modified Zn-Al mixed metal oxides (Zn-Al MMO@PDA/Pd NPs). Polydopamine was chosen as a biotemplate and a green reductant for the synthesis Pd NPs in situ without having any harsh reagent. Hitherto, this is the first design and biogenic synthesis of Pd NPs impregnated coordination on Zn-Al mixed metal oxides (Zn-Al MMO) and subsequent catalytic application towards the Suzuki-Miyaura coupling reactions. Subsequently, its physicochemical features were evaluated applying diverse methods like Field Emission Scanning Electron Microscopy (FE-SEM), X-ray elemental mapping (WDX), Energy Dispersive X-ray Spectroscopy (EDX) and X-Ray Diffraction (XRD) study. The Zn-Al MMO@PDA/Pd NPs nanocatalyst was isolated by centrifuger and stable enough to be reused for 8 consecutive times without considerable loss in activity.

Local coordination and electronic interactions of Pd/MXene via dual‐atom codoping with superior durability for efficient electrocatalytic ethanol oxidation

AbstractCatalyst design relies heavily on electronic metal‐support interactions, but the metal‐support interface with an uncontrollable electronic or coordination environment makes it challenging. Herein, we outline a promising approach for the rational design of catalysts involving heteroatoms as anchors for Pd nanoparticles for ethanol oxidation reaction (EOR) catalysis. The doped B and N atoms from dimethylamine borane (DB) occupy the position of the Ti3C2 lattice to anchor the supported Pd nanoparticles. The electrons transfer from the support to B atoms, and then to the metal Pd to form a stable electronic center. A strong electronic interaction can be produced and the d‐band center can be shifted down, driving Pd into the dominant metallic state and making Pd nanoparticles deposit uniformly on the support. As‐obtained Pd/DB–Ti3C2 exhibits superior durability to its counterpart (∼14.6% retention) with 91.1% retention after 2000 cycles, placing it among the top single metal anodic catalysts. Further, in situ Raman and density functional theory computations confirm that Pd/DB–Ti3C2 is capable of dehydrogenating ethanol at low reaction energies.

Pd nanoflakes epitaxially grown on defect MoS2 nanosheets for enhanced nitroarenes hydrogenation to anilines

Hydrogenation of nitroarenes to anilines under mild conditions is attractive from both theoretical and practical viewpoints. Here, high-performance catalyst with layered Pd nanoparticles epitaxially growing on ultrathin MoS2 nanosheets (Pd/MoS2) were prepared. It shows surprisingly high catalytic activity, selectivity and stability for hydrogenation of various nitroarenes to corresponding anilines; the turnover frequency is one or two magnitudes higher than conventional Pd-based catalysts. Surface sulfur vacancies are formed on MoS2 nanosheets with low formation energy barrier. These S vacancies provide efficient positions for adsorbing Pd atoms, which enables facile cleavage of N–O bond as result of strong interfacial electron interaction that decreases activation energy by 0.41 eV in comparison with conventional Pd catalysts. In situ spectroscopy and DFT calculation results reveal a dual-site mechanism, in which surface Pd sites adsorb and dissociate H2 into active H*, and then readily reacts with nearby activated nitroarene to form aniline on interfacial Pd-MoS2 sites.

Synergistic effect of PDA and PVP on nanosized Pd doped graphite felt/Ni electrode for promoting the electrocatalytic degradation of 2,4- dichlorophenoxyacetic acid

Reducing the mass transfer barrier for the diffusion of water and pollutants to Pd sites is an important measure to achieve efficient degradation of chlorinated organic compounds. Herein, a simple electroless deposition method for preparing a superhydrophilic nanosized Pd-loaded graphite felt/Ni electrode with the aid of the dispersibility of polyvinylpyrrolidone (PVP) and adhesiveness of polydopamine (PDA) is proposed. The GF/Ni/PDA/Pd-PVP electrode exhibited high electrocatalytic activity toward 2,4-dichlorophenoxyacetic acid (2,4-D) under the optimized conditions, namely degradation and dechlorination efficiencies of 90.5% and 88.53%, respectively, corresponding to 39% higher than that on the GF/Ni/Pd electrode. Experimental results revealed that PDA and PVP doping enhanced the hydrophilicity of the electrode, promoted the dispersibility of Pd nanoparticles (NPs), and the formation of Pd (111) and Ni (111) crystal facets. Compared to the electron-deficient PVP, the appropriate electron-donating ability of PDA promoted the formation of a suitable ratio of electro-deficient and electron-rich Pd, thus enhancing the production of Hads* and C-Cl scission. Moreover, theoretical calculation indicated that the doping of PDA and PVP optimized the adsorption energies of 2,4-D, Hads*, and the main dechlorination product PA, which was obtained via 4-electron transfer via Hads*. Therefore, this study provides a simple and feasible way to fabricate an efficient cathode for 2,4-D dechlorination.

Pd@CoFe Alloys on N-Doped Carbon Derived from Charred Tissue Paper as Synergistic Bifunctional Oxygen Electrocatalysts

Integrating more active components into a catalyst material could facilitate the development of multifunctional electrocatalysts for energy conversion and storage applications. In this study, we developed a multifunctional electrocatalyst, namely, Pd alloyed with Co-Fe deposited on N-doped mesoporous carbon derived from tissue paper (Pd@Co-Fe/N-TDC). The synergism in Pd@Co-Fe/N-TDC, stemming from the interatomic alloy between Pd and Co-Fe, N-doped mesoporous carbon with defective surfaces, distribution of polyhedral Pd nanoparticles, and strong metal-support interfacial interaction, resulted in significantly high electrocatalytic performance for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Pd@Co-Fe/N-TDC was found to be an efficient bifunctional oxygen electrocatalyst, and this was evidenced by a high onset potential (1.01 V) and kinetic current density (2.6 mA/cm2) for the ORR and by a low overpotential (296 mV) and a low Tafel slope value (38 mV/dec) for the OER, along with a small ΔE of 736 mV. The catalyst also exhibited high durability for both ORR and OER, even after 10000 and 5000 cycles, respectively. Theoretical assessment provides an insight into the synergism of active metal sites in Pd@Co-Fe/N-TDC, which showed its potential for use as a non-Pt electrocatalyst for energy applications.

Decarbonylation of Thioesters Catalyzed by CeO2- or Hydroxyapatite-Supported Ni, Pd, or Rh Nanoparticles

Decarbonylation of Thioesters Catalyzed by CeO2- or Hydroxyapatite-Supported Ni, Pd, or Rh Nanoparticles

Effect of carbon oxygen functionalization on the activity of Pd/C catalysts in hydrogenation reactions

AbstractThis paper presents a study on the effects of oxygen functionalities on a mesoporous and graphitized carbon support (GNP, Graphene Nanoplatelets), on the catalytic activity of Pd/GNP catalysts in hydrogenation reactions. A functionalization method in liquid phase has been employed, using different oxidants (HNO3, H2O2, KMnO4), with the aim to tune the amount and the type of introduced oxygen functionalities. Preformed Pd nanoparticles have been used as Pd‐precursor to limit differences in metal particle size and dispersion on differently functionalized carbon. The catalytic behaviour in benzaldehyde hydrogenation/hydrogenolysis to benzyl alcohol and toluene revealed that the introduction of oxygen functionalities has a generally detrimental effect. NMR relaxometry studies highlighted the weaker interaction between the carbonyl group and the functionalized Pd/GNP surface than the non–functionalized Pd/GNP demonstrating that the origin of the different catalytic activity lies on the first step of the reaction. O‐functionalities also impacted on the Pd0/Pd2+ ratio at the surface which is an established parameter correlated to the reaction rate.

Chitosan-functionalized poly(3-hydroxybutyrate) bead as a novel biosupport for palladium in the Suzuki cross-coupling reaction

The utilization of environmentally friendly biopolymer poly(3-hydroxybutyrate) (PHB) as a support for metal catalysts is an unexplored area. Herein, exploring a stable and recyclable heterogeneous palladium (Pd) catalyst based on PHB for the Suzuki cross-coupling reaction is an attractive topic. In this study, a novel hydrophobic and hydrophilic core-shell bead supported Pd catalyst was developed by using PHB particle as a hydrophobic rigid framework and hydrophilic chitosan (CS) as the surface of the supporting matrix to fix Pd nanoparticles (NPs). The results of structural characterization showed that the Pd NPs with a small average size of 2.3±0.82 nm were uniformly distributed on the surface of the PHB-CS bead with a Pd content of 0.12 wt%. This demonstrated that the PHB-CS bead created a stable coordinated environment for Pd fixation, preventing Pd leaching. Furthermore, the Pd@PHB-CS catalyst exhibited high catalytic efficiency with 99% conversion in the Suzuki reaction under mild conditions, using a solvent mixture of EtOH and H2O (1:1) for 0.5 h. It is worth noting that the catalyst exhibits excellent stability, and reusability. It can be reused five times without a significant reduction in activity while maintaining its structural integrity. The successful construction of Pd@PHB-CS will further expand the application of PHB in the field of metal catalysts and may help establish a green and environmentally friendly multifunctional platform for the development of highly recyclable heterogeneous catalysts containing metal nanoparticles.

Electrochemical determination of ascorbic acid using palladium supported on N-doped graphene quantum dot modified electrode

To precise screening concentration of ascorbic acid (AA), a novel electrochemical sensor was prepared using palladium nanoparticles decorated on nitrogen-doped graphene quantum dot modified glassy carbon electrode (PdNPs@N-GQD/GCE). For this purpose, nitrogen doped GQD nanoparticles (N-GQD) were synthesized from a citric acid condensation reaction in the presence of ethylenediamine and subsequently modified by palladium nanoparticles (PdNPs). The electrochemical behavior of AA was investigated, in which the oxidation peak appeared at 0 V related to the AA oxidation. Considering the synergistic effect of Pd nanoparticles as an active electrocatalyst, and N-GQD as an electron transfer accelerator and electrocatalytic activity improving agent, PdNPs@N-GQD hybrid materials showed excellent activity in the direct oxidation of AA. In the optimal conditions, the voltammetric response was linear in the range from 30 to 700 nM and the detection limit was calculated to be 23 nM. The validity and the efficiency of the proposed sensor were successfully tested and confirmed by measuring AA in real samples of chewing tablets, and fruit juice.

Voltammetric quantification of H:Pd ratio complicated by α↔β phase transition in PdHx: Electrodes with low Pd loadings

The Pd hydride (PdHx) is a typical system to study the fundamentals of solute intercalation and phase transformations or to determine the effect of strain on the rate of electrocatalytic reactions. A crucial methodological aspect, however, involves quantitatively determining the hydrogen-to-palladium atomic ratio (H:Pd) under experimental conditions where various incidental contributions to the total electrode charge are comparable to the charge spent for H adsorption/absorption and desorption. This is the case for electrodes with relatively low (dozens of μg/cm2) loadings of Pd on various porous supports, typically used to study the oxidation of small organic molecules or the reduction of oxygen in acidic or alkaline fuel cells. Ultra-low Pd loadings (often in the range of a few μg/cm2) are also typical for Pd nanoparticles on smooth supports, which are commonly considered as model systems for in situ structural studies of hydrogen sorption. To determine accurately the H content in Pd particles, we propose a technique based on analysis of charge disbalance at anodic and cathodic scans of a cyclic voltammogram, and also address the contribution of adsorbed H. To illustrate the possibilities and limitations of this technique, we present the voltametric study of thin electrodeposited Pd layers on glassy carbon and of a carbon-supported Pd catalyst.