Deposition Of Pd Nanoparticles Research Articles

Deposition of Pd, Pt, and PdPt Nanoparticles on TiO2 Powder Using Supercritical Fluid Reactive Deposition: Application in the Direct Synthesis of H2O2.

In this study, we investigated the catalytic properties of mono- and bimetallic palladium (Pd) and platinum (Pt) nanoparticles deposited via supercritical fluid reactive deposition (SFRD) on titanium dioxide (TiO2) powder. Transmission electron microscopy analyses verified that SFRD experiments performed at 353 K and 15.6 MPa enabled the deposition of uniform mono- and bimetallic nanoparticles smaller than 3 nm on TiO2. Electron-dispersive X-ray spectroscopy demonstrated the formation of alloy-type structures for the bimetallic PdPt nanoparticles. H2O2 is an excellent oxidizing reagent for the production of fine and bulk chemicals. However, until today, the design and preparation of catalysts with high H2O2 selectivity and productivity remain a great challenge. The focus of this study was on answering the questions of (a) whether the catalysts produced are suitable for the direct synthesis of hydrogen peroxide (H2O2) in the liquid phase and (b) how the metal type affects the catalytic properties. It was found that the metal type (Pd or Pt) influenced the catalytic performance strongly; the mean productivity of the mono- and bimetallic catalysts decreased in the following order: Pd > PdPt > Pt. Furthermore, all catalysts prepared by SFRD showed a significantly higher mean productivity compared to the catalyst prepared by incipient wetness impregnation.

Electroless Deposition of Palladium Nanoparticles on Graphdiyne Boosts Electrochemiluminescence.

Modulating the electronic structure of metal nanoparticles via metal-support interaction has attracted intense interest in the field of catalytic science. However, the roles of supporting substrates in regulating the catalytic properties of electrochemiluminescence (ECL) remain elusive. Here, we find that the use of graphdiyne (GDY) as the substrate for electroless deposition of Pd nanoparticles (Pd/GDY) produces the most pronounced anodic signal enhancement in luminol-dissolved oxygen (O2) ECL system as co-reactant accelerator over other carbon-based Pd composite nanomaterials. Pd/GDY exhibits electrocatalytic activity for the reduction of O2 through a four-electron pathway at approximately -0.059 V (vs Ag/AgCl) in neutral solution forming reactive oxygen species (ROS) as intermediates. The study shows that the interaction of Pd and GDY increases the amount and stability of ROS on the Pd/GDY electrode surface and promotes the reaction of ROS and luminol anion radical to generate excited luminol, which significantly boosts the luminol anodic ECL emission. Based on quenching of luminol ECL through the consumption of ROS by antioxidants, we develop a platform for the detection of intracellular antioxidants. This study provides an avenue for the development of efficient luminol ECL systems in neutral media and expands the biological application of ECL systems.

In situ synthesis of C–SiO2 enhanced Pd nanoparticles for catalytic dehydrogenation of formic acid

Formic acid (FA, HCOOH), as a liquid chemical hydrogen storage carrier with low cost, high hydrogen content, and convenient storage and transportation, has attracted extensive attention. Pd-based catalysts for hydrogen production from FA are easy to aggregate and deactivate in the reaction process, which hinders the further development of FA as a hydrogen storage carrier. Therefore, the exploitation of carriers with simple preparation methods and excellent performance can effectively improve the catalytic activity of Pd-based catalysts. Porous carbon and SiO2 have been widely used for their unique structural properties, and the preparation of composite carriers by combining the advantages of both is a current research hotspot. Herein, this work synthesized C–SiO2 for the deposition of Pd nanoparticles by a one-step method, and the obtained Pd/C–SiO2 exhibits a superior FA dehydrogenation activity with a turnover frequency value of 1278 h−1 and a favorable stability with only a slight decrease in activity after five cycles.

Ag/Cr-TiO2 and Pd/Cr-TiO2 for Organic Dyes Elimination and Treatment of Polluted River Water in Presence of Visible Light.

In this work, photocatalytic materials constituted by Cr-doped TiO2 (Cr-TiO2) decorated with noble metals show high effectiveness in the mineralization of Acid Orange 7 (AO7) and in the disinfection of real river water. The materials were firstly obtained by sol-gel method to get Cr-TiO2 that was subsequently modified by photochemical deposition of Ag or Pd nanoparticles (Ag/Cr-TiO2, Pd/Cr-TiO2). Chemical-physical characterization results evidenced that the noble metals were homogeneously distributed on the Cr-TiO2 surface. By using Pd(0.25%)/Cr-TiO2, the AO7 discoloration efficiency was about 91.4% after only 60 min of visible irradiation, which can be due to the lowest band gap of this material. Moreover, nitrates, chlorides, total hardness, and coliform bacteria content significantly decreased after the treatment of real river water samples (that is contaminated by industrial and domestic effluents) under UV and visible light irradiation in the presence of TiCrOx decorated with noble metals. One hundred percent of elimination rate for E. coli, total coliforms, and other enterobacteriaceae (without regrowth) was achieved by using Ag/Cr-TiO2 as photocatalyst.

Preparation of LSPR enhanced Z-scheme Pd/WO3@SnO2 for photocatalytic decomposition of organic compounds under simulated sunlight

The decoration of semiconductor photocatalysts with metal nanoparticles (NPs) is an efficient strategy for improving their performance via localized-surface-plasma-resonance (LSPR). For this study, a LSPR enhanced Z-scheme Pd/WO3@SnO2 photocatalyst was synthesized, which revealed excellent photocatalytic performance and reusability against Rhodamine B (RhB) with degradation rate of 100 % after 1 h under simulated sunlight. The reaction rate constants (k) of the Pd/WO3@SnO2 were ∼4.9, 3.5, and 2.1 times higher than those of the WO3, SnO2, and WO3@SnO2, respectively. In this Z-scheme-structure, the transfer efficacy of photogenerated electrons was significantly promoted due to integrated electric-field between the SnO2 and WO3, which was supported by experimental results and theoretical calculations. The deposited Pd nanoparticles served as an electron-transfer-bridge, as well as a LSPR excitation source, which played significant role in the degradation of RhB. The photodecomposition pathway of RhB was explored, and the toxicities of the intermediates were evaluated. Moreover, tetracycline (TC), chlortetracycline-hydrochloride (CTC), doxycycline-hydrate (DOX), and oxytetracycline (OTC) were tested as common antibiotic models to verify the effectiveness of the catalysts. The degradation efficiencies for TC, CTC, DOX, and OTC over Pd/WO3@SnO2 attained 90.98 %, 96.33 %, 75.37 %, and 50.90 %, respectively, under simulated sunlight, which confirmed its strong potential for the removal of recent pollutants. Experiments and electron paramagnetic resonance (EPR) tests indicated that •O2– served as the major active species in the photocatalysis process, while •OH and h+ played secondary roles. Finally, an LSPR enhanced direct Z-scheme mechanism was proposed. This study provides a rational design strategy for the development of more efficient Z-scheme photocatalysts that exploit the LSPR-effect for photodecomposition of organic pollutant compounds.

Pd/Chitosan Nanoparticle Catalysts Prepared by Solid Mortar Grinding for Hydrogenation of Nitroarenes

Herein, we report a rational and highly sustainable strategy for the gram-scale synthesis of solid chitosan polymer-supported palladium nanoparticles (Pd/Chit) without the use of toxic solvents or expensive purification processes. Pd nanoparticles (NPs) are deposited onto a chitosan polymer using both ascorbic acid and NaOH. The former served as a mild reducing agent in the conversion of PdCl2 to Pd NPs, and the latter was crucial in anchoring the resulting Pd NPs to the chitosan support during solid grinding. The combination of ligand adsorption kinetics measurements and Langmuir adsorption isotherm studies of Pd/Chit reveals that the deposited Pd NPs have a higher available surface area and a large number of accessible active sites, which is in sharp contrast with other Pd NP catalysts reported using solution methods. As a result, in the presence of NaBH4 as a hydrogen source, the Pd/Chit demonstrated enhanced catalytic activity for the reduction of a range of nitroarenes into corresponding amines. Furthermore, a kinetics investigation of the reduction of nitroarenes under optimal reaction conditions showed that Pd/Chit has substantially lower activation energy than other reported Pd NP catalysts. Because of the novel interface structure at the Pd–chitosan site as well as the greater number of accessible active sites at the Pd NP sites, the Pd/Chit possesses excellent catalytic activity and selectivity. The development of more renewable biopolymer-supported metal catalysts for heterogeneous catalysis may therefore be encouraged by the present scalable solid-state method for the sustainable synthesis of Pd/Chit catalysts.

Deposition of Pd nanoparticles on 2D Ni–Fe-MOF ultrathin nanosheets for efficient N-alkylation of amines by alcohols under visible light

Pd/Ni–Fe-MOF NSs exhibit superior performance for light initiated N-alkylation of amines by alcohols due to its ultrathin nanosheet morphology to shorten transport path for photogenerated charge carriers and maximize exposed catalytic active sites.

Sensitive detection of extracellular hydrogen peroxide using plasmon-enhanced electrochemical activity on Pd-tipped Au nanobipyramids.

The fabrication of electroactive nanostructures with high electron concentration and specific electron transport is crucial for electrochemical sensing. In this study, a plasmon-enhanced electrochemical sensor has been developed for the detection of extracellular hydrogen peroxide (H2O2) from cancer cells, utilizing Pd-tipped Au nanobipyramids (PTA NBPs) as the electrocatalysts. Plasmonic PTA NBPs were synthesized by depositing Pd nanoparticles onto the tips of Au nanobipyramids (Au NBPs). Under excitation of localized surface plasmon resonance (LSPR), the PTA NBPs generate high-energy electron-hole pairs (e-/h+) on their surface. The generated electrons (e-) significantly enhance the electrochemical reduction of H2O2. Based on this, a plasmon-enhanced H2O2 electrochemical sensor is constructed with high sensitivity (986.57 μA mM-1 cm-2), low detection limit (0.02 μM), wide linear range (0.1 μM to 980 μM), and good stability and repeatability. Moreover, this sensor also enables the measurement of extracellular H2O2 derived from cancer cells (MCF-7), highlighting its potential applications in cellular biology and biomedical research.

Controllable deposition of dispersed Pd nanoparticles on ZnO for Suzuki-Miyaura cross-coupling reactions.

Palladium nanoparticles find extensive applications in catalysis in both homogeneously and heterogeneously catalyzed processes. Supporting metal nanoparticles enhances their stability as compared to their unsupported counterparts. The role of catalytic support is increasingly recognized as crucial in determining the behaviour of these materials. However, controlling the deposition and anchoring of palladium nanoparticles remains a significant challenge. This contribution discusses the preparation of straight lines of palladium particles on zinc oxide by wet impregnation. This phenomenon is attributed to the highly stepped morphology of the employed ZnO that created steric anchoring sites to stabilize the metal particles. Palladium-based catalysts were evaluated for the valuable Suzuki-Miyaura cross-coupling reaction. The dispersed Pd/ZnO catalyst achieved a conversion rate of 86% with 100% selectivity, remarkably superior to that of the Pd/Al2O3 and Pd/TiO2 counterparts.

Electrodeposited Pd nanoparticles on polypyrole/nickel foam for efficient methanol oxidation

The present work describes the Ni foam (Ni–F)/polypyrrole (PPy)/palladium (Pd) (Ni–F/PPy/Pd) multilayered catalysts via a facile electrochemical technique. Potentiostatic deposition of PPy on the surface of Ni–F is followed by galvanostatic deposition of Pd nanoparticles on Ni–F/PPy acted as supports for electrochemical deposition of Pd nanoparticles. The produced catalysts are utilized for electrocatalytic methanol oxidation in alkaline media. Chronoamperometry (CA), cyclic voltammetry (CVs), and electrochemical impedance spectroscopy (EIS) techniques are used to examine the electrocatalytic performance of Ni–F/PPy/Pd based electrodes for methanol oxidation. The polypyrrole modification on Ni–F leads to an improvement in the electrocatalytic activity of the Ni-F/PPY-Pd catalysts toward methanol oxidation. As an open-pored, porous metal with high electrical conductivity, nickel foam produces a substantial amount of active area during the modification of Pd and polypyrrole, which results in significant catalytic activity and a rapid rate charge transfer reaction kinetics on methanol oxidation. The Ni–F/PPy/Pd10 catalyst exhibits enhanced specific activity than its counterparts and a reduced onset potential for methanol oxidation, as well as a low Tafel slope. Based on these results, Ni–F/PPy/Pd10 is suggested as a good material for the anode in the electrocatalytic oxidation of methanol.

Methanol-reduced Pd nanoparticles anchored on B,N-CDs@CNT hybrid for oxygen reduction reaction

The development of highly active oxygen reduction reaction (ORR) catalysts with low-loading of precious metals is imperative but remains a great challenge. Herein, Pd/B,N-CDs@CNT composite catalysts was designed with Pd nanoparticles immobilized on hybrid support composed of B,N-doped carbon dots (B,N-CDs) and the multi-wall carbon nanotubes (CNT) using a simple methanol reduction method. The deposited Pd nanoparticles exhibit clean surface, low crystallinity and surface distortion. The Pd/B,N-CDs@CNT catalyst shows significantly enhanced ORR activity, with the mass activity about 5–6 times higher than that of commercial Pt/C. Thus prominent ORR performance is mainly attributed to the unique microstructure of Pd nanoparticles. Moreover, the composited B,N-CDs and the doped B, N heteroatoms further improve the ORR performance, in which B,N-CDs supply more absorption sites, the formation of N–Pd facilitates the electron transfer, B doping can promote the adsorption of oxygenated species and weaken the strong interaction between Pd and C. Furthermore, the B, N co-doping plays a synergistic effect. This strategy provides a simple and mild method for designing highly efficient electrocatalysts with ultra-low precious metals in alkaline electrolytes.

Strategies for palladium nanoparticles formation on halloysite nanotubes and their performance in acetylene semi‑hydrogenation

Pd nanoparticles are widely applied in catalysis. In this work, the deposition of Pd nanoparticles onto halloysite (Hal) nanotubes from different Pd precursors and solvents has been investigated. The prepared Pd/Hal catalysts have been characterized by low-temperature N2 adsorption, transmission electron microscopy, zeta potential measurement, and tested in the hydrogenation of acetylene. On calcined Hal, the largest nanoparticles are formed in acid media, and the smallest are formed in non-aqueous one. Silanization of halloysite decreases absolute values of its zeta potential significantly and drops PdNPs size twice. Catalytic tests have shown that acetylene conversion and selectivity to ethylene depend on the deposition method, and the most active catalysts were prepared from Pd acetate dissolved in acetone. The lowest activity and highest selectivity to ethylene were demonstrated by the azine-modified halloysite, that could be related to Pd poisoning with nitrogen.

Hierarchically structured and highly active palladium-loaded Al-MIL-53-linked hybrid periodic mesoporous silica catalysts for Suzuki-Miyaura cross-coupling reaction

The rational design and precise preparation of hierarchically structured catalysts (HSCs) with an enhanced catalytic activity and reusability are still enormous challenges in material science and catalysis. Herein, a HSC Pd/Al-MIL-53@HOOC-SBA-15 was successfully prepared by the oriented growth of metal-organic framework Al-MIL-53 into/onto HOOC-SBA-15 via a hydrothermal technique and in-situ deposition of Pd nanoparticles reduced by NaBH4. Such a heterogeneous catalyst was applied to Suzuki-Miyaura cross-coupling reaction (CCR) of various aryl halides and phenylboronic acid. The results showed a highly catalytic performance over 99% conversion/yield, thanks to the crucial role of functional group, the synergistic effect of microporous-mesoporous structure, mesoporous confinement effect and microporous confinement effect. As a comparison, Pd/HOOC-SBA-15 and Pd/SBA-15 were also fabricated for C-C CCR, showing characteristic functional group-protected effect ensuring the stability and redeposition of Pd during catalysis. Based on experimental results, an order on catalytic activity and recyclability is Pd/Al-MIL-53@HOOC-SBA-15 > Pd/HOOC-SBA-15 > Pd/SBA-15 > Pd/Al2O3-C@SBA-15, revealing an excellent catalytic activity and high reusability of Pd/Al-MIL-53@HOOC-SBA-15. Combining with structure and composition of all catalysts, the leaching-redeposition mechanism can well explain highly catalytic performance and deactivation behavior in C-C CCR. This study provides an efficient strategy to prepare large-scale multi-composite HSCs for multi-functionalized catalytic applications.

Palladium‐Based Metal Organic Frameworks as Heterogeneous Catalysts for C−C Couplings

AbstractAmong the various cross coupling reactions, C−C cross coupling reaction has attracted many researchers to investigate in the last four decades. The continuous, constant, and consistent progress in this field fetched a Noble prize in 2010, showing the importance of this reaction in diversified fields. Among the various transition metals studied for this reaction, Pd is one of the metals that has exhibited the highest activity due to its unique features and reactivity. Although Pd‐based homogeneous catalyst was the preferred choice for many researchers, the field slowly diverted towards the development of Pd‐based heterogeneous catalysts for C−C coupling reactions. This is obviously due to the high cost of Pd precursor, its self‐deactivation. In this context, metal organic frameworks (MOFs) are one of the solid catalysts frequently employed as host matrix for the deposition of Pd(II) salts and Pd nanoparticles. This is due to the widespread possibilities available for the functionalization of MOFs and their stability during the synthetic procedure. This review provides the design and development of Pd‐based MOFs as heterogeneous catalysts for the C−C cross coupling reactions. After a brief introduction on MOFs and the importance of C−C coupling reactions, the main part of the review summarizes the catalytic data with respect to Pd(II) and Pd nanoparticles as active sites. The last section provides our views in this field for the further development in the near future.

Low-temperature control over deposition of ultrafine Pd nanoparticles on porous carbon nanosheets for highly efficient dehydrogenation of ammonia borane

The search for simply synthetic strategies of small-size metal nanoparticles is of significant relevance but still faces challenges. In this paper, a method of lowtemperature regulation (LTR) of ultrafine palladium nanoparticles deposited on porous carbon nanosheets is proposed for efficient dehydrogenation of ammonia borane. The LTR method might relieve the sintering of metal particles, thereby resulting in ultrafine Pd nanoparticles of 1.7 nm and their high dispersion on porous carbon. As suggested by the catalytic experiments hereby, Pd/NPC-LTR contributes to higher turnover frequencies of ammonia borane hydrolysis relative to most Pd-based catalysts reported previously. Furthermore, the catalytic performance could be further enhanced by the addition of NaOH under the same reaction conditions, with the hydrolysis completion time shortened by 2.5 times. Moreover, the recycle tests reveal that Pd/NPC-LTR catalyst has good stability and reusability in the hydrolysis of ammonia borane, preserving 70% of its initial catalytic activity even after 10 recycles. The insights reported here can be easily extended to slick preparation and rational design of Pd-catalysts for practical applications. • Low-temperature control over deposition of Pd NPs without any complicated treatments. • Highly dispersed and ultrafine Pd NPs are well deposited on porous carbon nanosheets. • Good performance for catalytic dehydrogenation of ammonia borane. • Highly stability and reusability even after 10 recycles.

Preparation, Characterization, and Catalytic Properties of Pd-Graphene Quantum Dot Catalysts

In this study, Pd-graphene quantum dot (Pd-GQD) catalysts were prepared by depositing Pd nanoparticles onto functionalized GQD surfaces, and their morphology and elemental composition were characterized using transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The as-prepared Pd-GQD was subsequently employed as a catalyst for the Heck and decarboxylative cross-coupling reactions and was found to exhibit higher catalytic activity than other reference systems. The expanded substrate scope of various substituted aryl iodides further proved that the GQD is an effective support for preparing new heterogeneous catalysts with improved catalytic performances.

Defect-dominated carbon deposited Pd nanoparticles enhanced catalytic performance of formic acid dehydrogenation

The defect-rich characteristic nanostructure carbon favors the changing polarity and electron distribution in carbon matrix, thus facilitating an efficient adsorption of ions. Herein, a B,N,F-tridoped carbon material is successfully prepared on defect-rich sites by directly calcining two sodium salts, namely ethylenediaminetetraacetic acid tetrasodium salt (Na4EDTA) and ammonium tetrafluoroborate (NH4BF4). B refers to electron-donating atoms while F and N are electron-accepting atoms. The co-existence of electron-donating and electron-accepting atoms causes an asymmetrical spin and charge density, favoring palladium nanoparticles (Pd NPs) well dispersed on the carbon matrix. The heteroatoms efficiently control over the growth of Pd NPs and regulate the internal electron density. The catalytic performance is significantly enhanced with the obtained Pd/BNF-C catalyst for formic acid dehydrogenation, which has a lower activation barrier (36.4 kJ/mol) and a better reusability than those of free-heteroatom catalysts. The efficiency might be attributed to the strong interaction between Pd NPs and heteroatoms, and the electrons transfer from carbon material to Pd NPs, with benefits including the significant coupling effect of B,N,F-tridoping down to the atomic scale, abundant surface active defects, in-plane nanopore defects and more adjacent metal active sites.

Functionalized rGO-Pd nanocomposites as high-performance catalysts for hydrogen generation via water electrolysis

Designing an efficient electrocatalyst for hydrogen evolution reaction (HER) is an important research area among the energy-related topics. In our study, the surface of the glassy carbon electrode (GCE) has been modified with reduced graphene oxide/(3-aminopropyl) triethoxysilane/Schiff base (rGO/APTES/Scb) composite structure. Palladium (Pd), which is preferred due to its high catalytic activity in HER process, has been embedded on this composite surface by two different methods. The first nanocomposite was obtained by depositing Pd nanoparticles electrochemically on the rGO/APTES/Scb surface, referred to as rGO/APTES/Scb/Pd Nc1. The other nanocomposite was synthesized by complexing Pd2+ with GO/APTES/Scb and then electrochemically reduced after applied to the electrode surface to obtain rGO/APTES/Scb/Pd Nc2. Conventional characterization techniques have been used to determine the surface structure, morphology and the chemical composition of the as-prepared nanocomposites. The results have shown the different distribution of Pd nanoparticles on both electrodes and that obtained from electrochemical tests for HER were also compatible in themselves. Although both nanocomposites showed high performance and stability, rGO/APTES/Scb/Pd Nc2 exhibited slightly better catalytic activity with an onset potential of -190 mV, a Tafel slope of 129 mV of per decade and achieving a current density of 10 mA cm−2 at an overpotential of -148 mV.

Pd(/Fe3O4)-on-ZIFs: nanoparticle deposition on (nano-)MOFs from ionic liquids

Selected ionic liquids are efficient media for deposition of Pd nanoparticles on nano- or micro- (100–2500 nm) crystals of different zeolitic imidazolate frameworks at 180-230 °C (MW, 1–10 min).

Reduction deposition of Pd nanoparticles on ZnO flowers used for photodegradation of methylene blue and methyl orange under UV light

ZnO flowers decorated with Pd nanoparticles on top were synthesized by a reduction deposition method using NaBH4 as a reducing reagent for efficient degradation of methylene blue (MB) and methyl orange (MO) under UV light irradiation. Pd nanoparticles uniformly anchored on the surface of ZnO petals for improving photocatalytic activities by preventing the recombination of photo-excited electrons–photo-induced holes. Heterostructure Pd/ZnO nanocomposite flowers have photocatalytic activity for degrading of MB and MO solution under UV light irradiation better than pure ZnO flowers. In this research, heterostructure 5% Pd/ZnO flowers have 1.5 and 4.7 times for MB and MO photodegradation over pure ZnO flowers because of the enhanced separation efficiency of electron–hole pairs containing in the heterostructure Pd/ZnO flowers.