Supported Palladium Nanoparticles Research Articles

Insights Into Electrocatalytic Hydrogenation of Furfural on Nanoparticulate Pd/C Under Acidic Conditions

AbstractIn this work, we present an insight into the mechanism of electrochemical hydrogenation of furfural on carbon supported palladium nanoparticles. By directly coupling electrochemistry with mass spectrometry, we were able to, for the first time, deconvolute the hydrogen evolution reaction and electrochemical hydrogenation by measuring the mass signal for hydrogen and 2‐methylfuran. This approach also allowed us to extract the Tafel slopes for each reaction and get insights into mechanisms. The results indicate that the hydrogenation occurs by a Langmuir–Hinshelwood type process rather than by proton‐coupled electron transfer. Further findings recognize the blocking character of furfuryl alcohol (FA) where the latter or one of its intermediates blocks the electrochemical hydrogenation. Additionally, FA is shown to be a precursor for 2‐methyl furan formation. Accordingly, specific guidelines towards improvement of reaction performance are suggested.

Ultrafine Pd nanoparticles confined in naphthalene-based covalent triazine frameworks for efficient and stable hydrogen production from formic acid

Formic acid (FA) is considered as a kind of promising hydrogen storage materials due to its economic feasibility, safety, stability and high hydrogen density. Nevertheless, it is a challenge to design a high-performance catalyst with high activity, selectivity and stability for the dehydrogenation of FA to generate hydrogen (H2). Herein, a range of covalent triazine frameworks (CTFs including 1,8-CTF, 1,5-CTF and 2,3-CTF) with abundant nitrogen atoms are developed to support palladium nanoparticles for efficiently catalyzing FA dehydrogenation. Ultrasmall palladium nanoparticles with a size of 1.2 ± 0.3 nm showed near 100 % H2 selectivity and high catalytic activity in FA dehydrogenation supported by 1,8-CTF. The activation energy of FA dehydrogenation catalyzed by Pd/1,8-CTF reaches 26.17 kJ·mol−1. In addition, Pd/1,8-CTF exhibits high stability and easy recyclability, and the catalytic activity is maintained even after 6 cycles. This work gives a feasible strategy to develop high-efficiency and selective nanocatalysts for H2 production from FA dehydrogenation.

Iridium Single Atoms to Nanoparticles: Nurturing the Local Synergy with Cobalt-Oxide Supported Palladium Nanoparticles for Oxygen Reduction Reaction.

A ternary catalyst comprising Iridium (Ir) single-atoms (SA)s decorated on the Co-oxide supported palladium (Pd)nanoparticles (denoted as CPI-SA) is developed in this work. The CPI-SA with 1wt.% of Ir exhibits unprecedented high mass activity (MA) of 7173 and 770mA mgIr -1, respectively, at 0.85 and 0.90V versus RHE in alkaline ORR (0.1m KOH), outperforming the commercial Johnson Matthey Pt catalyst (J.M.-Pt/C; 20wt.% Pt) by 107-folds. More importantly, the high structural reliability of the Ir single-atoms endows the CPI-SA with outstanding durability, where it shows progressively increasing MA of 13 342 and 1372mA mgIr -1, respectively, at 0.85 and 0.90V versus RHE up to 69 000 cycles (3 months) in the accelerated degradation test (ADT). Evidence from the in situ partial fluorescence yield X-ray absorption spectroscopy (PFY-XAS) and the electrochemical analysis indicate that the Ir single-atoms and adjacent Pd domains synergistically promote the O2 splitting and subsequent desorption of hydroxide ions (OH-), respectively. Whereas the Co-atoms underneath serve as electron injectors to boost the ORR activity of the Ir single-atoms. Besides, a progressive and sharp drop in the ORR performance is observed when Ir-clusters and Ir nanoparticles are decorated on the Co-oxide-supported Pd nanoparticles.

Mesoporous organic resin supported palladium nanoparticles for efficient hydrodeoxygenation of vanillin

Resorcinol 1,4-phthalaldehyde resin (RPR) was successfully synthesized using a solvent-free self-assembly method employing a template (F127) and a mixture of resorcinol and 14-phthalaldehyde. After the removal of the template (F127) by heating, the PRR exhibited an ordered mesoporous structure with a size of approximately 5.8 nm. After impregnating with Pd species, a RPR supported Pd catalyst (Pd/RPR) was finally obtained, which demonstrated outstanding catalytic performance and good stability in the hydrodeoxygenation of vanillin. With an optimal catalyst, 100% conversion of vanillin and 96.7% selectivity for 2-methoxy-4-methylphenol were achieved under the reaction conditions of 2 MPa H2 in ethanol at 90 ℃ over 4 hours. The superior catalytic properties of Pd/RPR with high activity and stability are anticipated to be significant for future biofuel upgrades.

Furaldehyde-based magnetic supported palladium nanoparticles as an efficient heterogeneous catalyst for Mizoroki–Heck cross-coupling reaction

Novel furaldehyde-based magnetic nanoparticles are used as an efficient catalyst for the Mizoroki–Heck reaction of arylhalide and olefins.

Efficient synthesis of glycerol carbonate by doping metallic copper in palladium-catalyzed glycerol system for carbonylation reaction

The synergistic effect between copper and palladium promotes electron transport by using ZIF-8-derived Cu–NC materials to support palladium nanoparticles, which plays a crucial role in the ringing of glycerol carbonate.

Anthracene-based covalent organic framework supported palladium nanoparticles for visible-light-mediated Suzuki–Miyaura cross-coupling

Anthracene-based covalent organic framework (COF) anchoring Pd nanoparticles photocatalyzed Suzuki–Miyaura coupling of arylbromides and arylboronic acids in water under blue LED irradiation at room temperature.

Aerobic bacteria-supported biohybrid palladium catalysts for efficient cross-coupling reactions

Palladium-based catalysts are of key importance in organic synthesis due to their versatility and tolerance for a wide range of functional groups. However, their use challenged by increasing sustainability issues and complex preparation methods. Consequently, the development of new heterogeneous catalysts with enhanced sustainability is of significant interest. Typically, the synthesis of carbon supports for palladium is associated with high energy consumption or the generation of substantial chemical waste, prompting extensive research into the creation of sustainable biological supports. In this study, the potential use of aerobic bacterial cells as a support for palladium nanoparticles was explored, using Paracoccus yeei VKM B-3302 as a model organism. Electron microscopy, powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) studies demonstrated the formation of palladium particles on the cell surface as well as inside microorganisms following deposition from a solution. Control experiments established that bacterial cells do not interact with either the reactants or the products of selected cross-coupling processes. Furthermore, bacteria do not affect the analysis of reaction mixtures by nuclear magnetic resonance (NMR) spectroscopy and gas chromatography-mass spectrometry (GC–MS). At the same time, palladium/Paracoccus yeei demonstrated efficient catalysis of the Mizoroki-Heck and Suzuki-Miyaura reactions, yielding results comparable to commercial palladium on carbon (Pd/C) catalysts. Employing a fresh start procedure and catalyst separation method, the catalyst was successfully recycled and reused across five cycles, maintaining good catalytic activity. In a broader aspect, bacteria-supported biohybrid palladium catalysts can represent a new type of catalysts worth to explore in a number of processes, where sustainability issues are concerned.

The Origin of the Size Effect in the Oxidation of CO on Supported Palladium Nanoparticles

Two Pd/TiO2 catalysts with mean particle sizes of 1 and 3 nm were prepared and tested in the low-temperature oxidation of CO. It was found that the first catalyst with higher dispersion is more active. Turnover frequencies varied for these catalysts by almost six times. In contrast, the apparent activation energy of the oxidation of CO on the catalyst with smaller Pd nanoparticles was estimated at 76 kJ/mol, and for the catalyst with larger Pd nanoparticles at 58 kJ/mol. According to in situ XANES studies, the particle size effect originates from the oxidation of small palladium nanoparticles under reaction conditions, whereas larger nanoparticles are stable and consist of palladium atoms mainly in the metallic state. Palladium oxide is more active in the low-temperature oxidation of CO than metallic palladium. This means that the origin of size-dependent activity of Pd nanoparticles in the low-temperature oxidation of CO is associated with the change in the chemical composition of nanoparticles that leads to a change in the reaction mechanism and, as a result, in their activity.

Oxygen vacancy-driven strong metal-support interactions on AuPd/TiO2 catalysts for high-efficient air-oxidation of 5-hydroxymethylfurfural

The regulation ofstrong metal-support interactions (SMSI) has emerged as a powerful strategy in boosting catalytic activity and controlling product selectivity. However, directly tuning the metal-supportinteractions in oxide supported metal nanocatalysts remains challenging. Herein, citric acid (CA)‑assisted synthesized TiO2 layer on halloysite nanotubes (HNTs) with varied oxygen vacancies (Ov) concentrations was designed for loading AuPd nanoparticles. SMSI between the AuPd nanoparticles and the TiO2-xCA@HNTs support was successfully induced by adjustable Ov concentrations. The synthesized catalyst was employed for air-oxidation of bio-based 5-hydroxymethylfurfural (HMF) to bioplastic monomer 2,5-furandicarboxylic acid (FDCA) in water. A satisfactory FDCA yield of 98.4 %, accompany with an outstanding FDCA formation rate of 900.9 mmol·g−1·h−1 and an excellent TOF value at 441.2 h−1 was afforded. Based on catalysts characterizations and experimental studies, the catalytic performance was significantly affected by Ov concentrations. The kinetic study showed that the supported gold nanoparticles in alkaline environment had strong aldehyde oxidation activity but weak alcohol oxidation ability. On the contrary, supported palladium nanoparticles were more conducive to alcohol oxidation. This imbalance was overcome by the loading of AuPd nanoparticles, which enhanced the activity for air-oxidation of HMF. Mechanistic studies demonstrated that the stronginteractions between noble metal nanocatalysts and supports were regulated by Ov, which not only increased the adsorption capacity of the substrate and crucial intermediate, but also facilitated the adsorption and activation of molecular oxygen to generate oxygen active species of superoxide radicals. The possible catalytic mechanism for air-oxidation of HMF over Ov-driven SMSI on the obtained catalysts was proposed. This work sheds lights on the design of supported metal catalysts with SMSI for the catalytic upgrading of biomass-derived platform chemicals.

Polysaccharide/Silica Microcapsules Prepared via Ionic Gelation Combined with Spray Drying: Application in the Release of Hydrophilic Substances and Catalysis.

Polysaccharide/silica hybrid microcapsules were prepared using ionic gelation followed by spray-drying. Chitosan and alginate were used as biopolymer matrices, and in situ prepared silica was used as a structuring additive. The prepared microparticles were used in two very different applications: the encapsulation of hydrophilic molecules, and as a support for palladium nanoparticles used as catalysts for a model organic reaction, namely the reduction of p-nitrophenol by sodium borhydride. In the first application, erioglaucine disodium salt, taken as a model hydrophilic substance, was encapsulated in situ during the preparation of the microparticles. The results indicate that the presence of silica nanostructures, integrated within the polymer matrix, affect the morphology and the stability of the particles, retarding the release of the encapsulated substance. In the second application, chloropalladate was complexed on the surface of chitosan microparticles, and palladium(II) was subsequently reduced to palladium(0) to obtain heterogeneous catalysts with an excellent performance.

Mechanochemistry through Extrusion: Opportunities for Nanomaterials Design and Catalysis in the Continuous Mode

The potentialities of mechanochemistry trough extrusion have been investigated for the design of nanosized catalysts and their use in C-C bond-forming reactions. The mechanochemical approach proved successful for the synthesis of supported palladium nanoparticles with mean diameter within 6–10 nm, achieved by the reduction of Pd(II) acetate with ethylene glycol, in the absence of any solvent. A mesoporous N-doped carbon derived from chitin as a renewable biopolymer, was used as a support. Thereafter, the resulting nanomaterials were tested as catalysts to implement a second extrusion based-protocol for the Suzuki-Miyaura cross-coupling reaction of iodobenzene and phenylboronic acid. The conversion and the selectivity of the reaction were 81% and >99%, respectively, with a productivity of the desired derivative, biphenyl, of 41 mmol gcat−1 h−1.

Fluorine spillover for ceria- vs silica-supported palladium nanoparticles: A MD study using machine learning potentials.

Supported metallic nanoparticles play a central role in catalysis. However, predictive modeling is particularly challenging due to the structural and dynamic complexity of the nanoparticle and its interface with the support, given that the sizes of interest are often well beyond those accessible via traditional abinitio methods. With recent advances in machine learning, it is now feasible to perform MD simulations with potentials retaining near-density-functional theory (DFT) accuracy, which can elucidate the growth and relaxation of supported metal nanoparticles, as well as reactions on those catalysts, at temperatures and time scales approaching those relevant to experiments. Furthermore, the surfaces of the support materials can also be modeled realistically through simulated annealing to include effects such as defects and amorphous structures. We study the adsorption of fluorine atoms on ceria and silica supported palladium nanoparticles using machine learning potential trained by DFT data using the DeePMD framework. We show defects on ceria and Pd/ceria interfaces are crucial for the initial adsorption of fluorine, while the interplay between Pd and ceria and the reverse oxygen migration from ceria to Pd control spillover of fluorine from Pd to ceria at later stages. In contrast, silica supports do not induce fluorine spillover from Pd particles.

The Effect of Reducing Agent for Synthesizing Palladium Nanoparticle on Carbon Nanotube Support and Its Superior Catalytic Activity towards Methanol Oxidation Reaction

In this report, we have synthesized carbon nanotube supported palladium nanoparticles (CNT-Pd) by using different reducing agents such as sodium borohydride (SBH), hydrazine monohydrate (HY) and ascorbic acid (AA) for the methanol oxidation reaction (MOR) in alkaline media. The elemental and morphological properties of all catalysts are verified by HRTEM, XPS, and XRD. From the HRTEM images, it is found that CNT-Pd reduced by sodium borohydride CNT-Pd (SBH) exhibited a narrow size distribution of Pd nanoparticles (PdNPs) with an average size of 3.15 nm. The role of the reducing agents (SBH, HY, and AA) is investigated by applying them as anode catalysts for the methanol oxidation reaction (MOR) and it is found that the reducing agent remarkably affected the electrochemical activities. CNT-Pd (SBH) catalysts show the superior catalytic activity and durability towards MOR among all catalysts, which may be due to the Pd NPs in CNT-Pd (SBH) having a perfect crystal structure with a narrow size distribution.

Corncob-derived nanocellulose-supported palladium nanoparticles towards catalytic reduction of 4-nitrophenol

This study proposed the efficient extraction of nanocellulose from an agricultural residue and the facile immobilization of metal nanoparticles on the surface of nanocellulose without using any external surfactants. In which, corncob was successively treated by an alkaline aqueous solution, a bleaching agent, and a strong acid in order to achieve nanocellulose, which was subsequently served as a support for palladium nanoparticles (PdNPs/NC). Nanocellulose and PdNPs/NC were thoroughly examined involving Fourier-transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Such successive chemical treatments of corncob yielded nanocellulose with crystallinity index of over 90 %, and palladium nanoparticles (4.9 % wt. Pd) were successfully immobilized on cellulose nanofibrils (∼50 nm in diameter, micrometers in length). Such a catalytic system (PdNPs/NC) was utilized in the selective reduction of 4-nitrophenol to form 4-aminophenol at room-temperature, complying the pseudo-first-order kinetics (k = 0.1144 min−1), relative to a turnover frequency (TOF) of 1.91 h−1, validating the high reactivity of the newly-generated nanocatalyst.

Evolution of surface and bulk structure of supported palladium nanoparticles by in situ X-ray absorption and infrared spectroscopies: Effect of temperature, CO and CH4 gas

Interaction of CO and CH4 with palladium is a relevant process in numerous catalytic reactions, which may induce structural changes in the metal affecting its catalytic properties This work establishes a systematic study of the evolution of the atomic and electronic structure in alumina- and carbon-supported palladium nanoparticles in presence of CO and CH4 gases at temperatures from 50 to 350 °C by a combination of in situ X-ray absorption and infrared spectroscopies. Immediate adsorption of CO molecules with formation of surface carbon deposits due to the disproportionation reaction occurs at low temperatures, while above 250 °C, active formation of bulk palladium carbide is observed. In CH4 the later process starts only at ca. 350 °C. Reduction of palladium and contraction of the Pd-Pd interatomic distances were observed with increasing temperature irrespective of the gas atmosphere, including the inert one, particle size and the type of support. For carbon supported samples formation of palladium carbide occurred above 200 °C due to the decomposition of the support.

Sewage Sludge Activated Carbon as an Adsorbent and Catalytic Support: Evaluation of Nitrate Removal and Suzuki‐Miyaura Cross‐Coupling

AbstractThis manuscript reports the valorization of sewage sludge with the production of activated carbon. Thus, a series of 11 adsorbents are produced, activated with different substances (salt, acid, and base), and their adsorptive properties are carefully evaluated. The C6 series of activated carbons prove to be very efficient for removing nitrate anions from aqueous medium and, due to this, it is evaluated as a catalytic support for palladium nanoparticles. The generated solid, named Pd@CA6F, is the first report of a catalyst containing activated carbon from sewage sludge that is efficient in the Suzuki‐Miyaura cross‐coupling. The catalytic system developed is eco‐friendly, phosphine‐free, and of low cost. Good yields are obtained in the coupling of aryl iodides with phenylboronic acid in a short time. The same catalyst load could be recycled for up to ten times.

Fe3O4-carbon spheres core–shell supported palladium nanoparticles: A robust and recyclable catalyst for suzuki coupling reaction

Suzuki-Miyaura (S-M) is regarded the most powerful way for synthesis biaryls, triaryls, or incorporating of substituted aryl moieties in organic preparation by the cross-coupling of aryl boronic acid with aryl halides using the Pd catalyst. This work reports the combining of the hydrothermal and microwave-assisted protocol to convert the glucose to magnetic carbon spheres (Fe3O4-CSPs) decorated with Pd nanoparticles (NPs) as the catalyst for Suzuki-Miyaura cross-coupling reactions. The physicochemical properties in the produced composite were examined using FESEM, HRTEM, nitrogen isotherms, Raman spectroscopy, FTIR, XPS, and XRD. The as-fabricated composite Pd/Fe3O4-CSPs is mostly spherical with a core–shell structure and possesses a great surface area of 253.2 m2·g−1. Its catalytic performance demonstrates that the composite has excellent stability and high tolerance Suzuki-Miyaura cross-coupling reactions in 30 min at 80 °C. Both activated and deactivated aryl halides provided excellent yield. The as-fabricated catalyst was recycled for up to four catalytic cycles without a substantial decline in performance. Moreover, this research offers a facile roadmap for synthesizing Pd/Fe3O4-CSPs composites and promoting the practical implementation of Pd/Fe3O4-CSPs catalysts for organic transformation processes.

A novel core@double shell magnetic nitrogen-doped carbon nanotubes as a support for palladium nanoparticles: A highly efficient magnetic catalyst in the direct reductive coupling of nitroarenes and alcohols

Palladium nanoparticles anchored to the core-double shell magnetic nitrogen-doped carbon (Fe3O4@N-C) nanotubes have been successfully synthesized and characterized. It is possible to load palladium nanoparticles inside and outside of the nanotube. The catalytic performance of the as-prepared nanohybrids was evaluated by the one-pot synthesis of the imine and secondary amine directly from the readily available and stable nitrobenzene and benzyl alcohol precursors under exogenous base and solvent-free conditions. It showed excellent performance in this cascade reaction, as measured by high nitrobenzene conversion (99%) and turnover frequency (3.96 h−1).

Triazole-functionalized hydrochar-stabilized Pd nanocatalyst for ullmann coupling

Biomass valorization is essential, particularly in emerging countries. Here, hydrochar from arabica coffee straw was functionalized with a triazole group (HD-TRz) for use as a support of palladium nanoparticles (PdNPs-HD-TRz) applied in the Ullmann coupling reaction for the first time. It provided remarkably excellent selectivities, conversions at a temperature as low as 45 °C and catalyst recyclability, surpassing previous literature performances. Hydrochar was obtained by one-pot reaction via hydrothermal synthesis, using NaOH solution as activating agent and functionalized with a 1,3-triazole group by CuAAC “click” reaction. The PdNPs were prepared via reduction of hydrochar-bound Pd(II) using NaBH4. Hydrochar functionalization was monitored by infrared spectroscopy, and X-ray diffraction (XRD) allowed to observe carbon and palladium planes in hydrochar and PdNPs HD-TRz structures. The PdNPs presented a spherical shape with 2.1 ± 0.1 nm size, homogeneously distributed in the carbon coverslips. The HD-TRz-supported PdNPs were used as a catalyst in the Ullmann reaction of iodobenzene, using ethanol as solvent with 100% of conversion and 91% selectivity at 45 °C. The material was reused, presenting 100% of conversion and selectivities of 92, 84 and 73% for the 1st, 2nd and 3rd cycle, respectively. The scope of the reaction was expanded to other molecules showing the potential of this and other triazole-hydrochar-supported nanocatalysts.