Supported Metal Nanoparticles Research Articles

Real-Time Simulation of the Reaction Kinetics of Supported Metal Nanoparticles.

A common issue with supported metal catalysts is the sintering of metal nanoparticles, resulting in catalyst deactivation. In this study, we propose a theoretical framework for realizing a real-time simulation of the reactivity of supported metal nanoparticles during the sintering process, combining density functional theory calculations, microkinetic modeling, Wulff-Kaichew construction, and sintering kinetic simulations. To validate our approach, we demonstrate its feasibility on α-Al2O3(0001)-supported Ag nanoparticles, where the simulated sintering behavior and ethylene epoxidation reaction rate as a function of time show qualitative agreement with experimental observation. Our proposed theoretical approach can be employed to screen out the promising microstructure feature of α-Al2O3 for stable supported Ag NPs, including the surface orientation and promoter species modified on it. The outlined approach of this work may be applied to a range of different thermocatalytic reactions other than ethylene epoxidation and provide guidance for the development of supported metal catalysts with long-term stability.

Precise Size Determination of Supported Catalyst Nanoparticles via Generative AI and Scanning Transmission Electron Microscopy.

Transmission electron microscopy (TEM) plays a crucial role in heterogeneous catalysis for assessing the size distribution of supported metal nanoparticles. Typically, nanoparticle size is quantified by measuring the diameter under the assumption of spherical geometry, a simplification that limits the precision needed for advancing synthesis-structure-performance relationships. Currently, there is a lack of techniques that can reliably extract more meaningful information from atomically resolved TEM images, like nuclearity or geometry. Here, cycle-consistent generative adversarial networks (CycleGANs) are explored to bridge experimental and simulated images, directly linking experimental observations with information from their underlying atomic structure. Using the versatile Pt/CeO2 (Pt particles centered ≈2nm) catalyst synthesized by impregnation, large datasets of experimental scanning transmission electron micrographs and physical image simulations are created to train a CycleGAN. A subsequent size-estimation network is developed to determine the nuclearity of imaged nanoparticles, providing plausible estimates for ≈70% of experimentally observed particles. This automatic approach enables precise size determination of supported nanoparticle-based catalysts overcoming crystal orientation limitations of conventional techniques, promising high accuracy with sufficient training data. Tools like this are envisioned to be of great use in designing and characterizing catalytic materials with improved atomic precision.

Ru/MgO-catalysed selective aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid

Biomass valorisation through the selective oxidation of carbohydrate and lipid derivatives offers access to an array of platform chemicals through energy- and atom-efficient catalytic processes. Supported metal nanoparticles are promising catalysts for the aerobic selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA), but typically require strong liquid base to achieve high selectivity. Here, we explore the utility of MgO as a solid base support for the Ru-catalysed aerobic oxidation of HMF, obtaining 68% FDCA yield at 160°C and 1.5 MPa of O2 using <1 mol-% metal.

In-situ observation of defects evolution of graphene nanoflakes in Pt/C catalyst for boosting ORR performance

The structural stability of supported metal nanoparticles determines the activity and longevity of heterogeneous catalysts. Unfortunately, the chemical/thermal working environment inevitably accelerates metal sintering to larger crystallites that leads to the degradation of catalytic performance. Here, we demonstrate that the distribution of defects in carbon support as an inherent parameter plays a crucial role in catalyst sintering. Based on in-situ transmission electron microscopy studies, the strong metal-support interaction between platinum (Pt) nanoparticles and defect-rich graphene nanoflakes largely suppresses metal sintering up to 700 °C. Particularly, the optimal carbon support can be achieved in the annealing process, in which the mass transfer and charge transport can be enhanced by accurately manipulating the distribution of defects in carbon matrix and graphitization degree. It is worth noting that the screened Pt/GNs-300 exhibits impressive oxygen reduction reaction performance with high half-wave potential (0.91 V), mass activity (108.1 A g–1Pt) and excellent stability. By its ascendancy in ORR, the Pt/GNs-300 exhibits a high open-circuit voltage of 1.41 V and a maximum power density of 198.6 mW cm−2 in Zn-air battery, implying its brilliant practicability. This work paves a pathway for achieving sinter-resistant metal-loaded catalysts in energy electrocatalysis.

Oxygen vacancies promoted hydrogen production from methanol aqueous phase reforming over MgAl−LDHs supported plasmonic Ru nanoparticles catalyst

Catalytic aqueous phase reforming of methanol is a promising process for the sustainable hydrogen production. The search for highly efficient heterogeneous catalyst is a topic of interest. Herein, we report oxygen vacancies enriched MgAl−LDHs supported plasmonic Ru nanoparticles catalyst exhibit excellent photocatalytic performance for efficient hydrogen production at 150 ºC under light irradiation. Characterizations demonstrate abundant oxygen vacancies are introduced into MgAl−LDHs via “memory effect”. The local electron transfer from oxygen vacancies of the MgAl−LDHs to the Ru nanoparticles leading the formation of electron-rich Ru species, which promote the dehydrogenation of methanol under light irradiation. In situ DRIFTS demonstrated a redox mechanism of water-gas shift reaction due to the existence of oxygen vacancies, which resulted a faster hydrogen production rate. This work displays a facile strategy for synthesis of oxygen vacancies rich LDH supported metal nanoparticles catalysts and deep understanding into the pathway and mechanism toward the effective hydrogen production.

Recent Progress on Covalent Organic Frameworks Supporting Metal Nanoparticles as Promising Materials for Nitrophenol Reduction

With the utilization of nitrophenols in manufacturing various materials and the expansion of industry, nitrophenols have emerged as water pollutants that pose significant risks to both humans and the environment. Therefore, it is imperative to convert nitrophenols into aminophenols, which are less toxic. This conversion process is achieved through the use of noble metal nanoparticles, such as gold, silver, copper, and palladium. The primary challenge with noble metal nanoparticles lies in their accumulation and deactivation, leading to a decrease in catalyst activity. Covalent organic frameworks (COFs) are materials characterized by a crystalline structure, good stability, and high porosity with active sites. These properties make them ideal substrates for noble metal nanoparticles, enhancing catalytic activity. This overview explores various articles that focus on the synthesis of catalysts containing noble metal nanoparticles attached to COFs as substrates to reduce nitrophenols to aminophenols.

Efficient Electrochemical Reduction through Flow Cells Using Spherical-Polymer Based Carbon Supported Catalysts as Fixed-Bed Electrode

The transition to economically friendly feedstocks and the electrification of chemical synthesis reactions gained much attention in the recent years. To be able to compete with the conventional processes, it is crucial not only to concentrate on the electrochemical reactions itself but also to constantly improve the reactor concepts. A vast variety of designs are imaginable and already well-described – from a simple, undivided beaker cell setup to a divided flow cell with separate electrolytes at cathode and anode. [1] As electrode material not only flat metal electrodes are studied, but also the concept of using carbon supported metal nanoparticles is well-known to employ high dispersion to lower the total amount of required metal. [2,3] While there are already commercial flow reactors and electrodes available for electrosynthesis with flat standard electrodes, reactors using a fixed-bed of porous carbon with nanodispersed metals as electrode just recently started to attract attention. [4] Dealing with the pressure drop over the catalyst bed, while the electrical contact is still ensured, are key challenges for this reactor design. Spherical polymer-based carbons (SPBC) combine porous carbons properties with a high purity and especially spherical character. [5] While these advantages led already to commercial products for chromatographic applications (e.g. Carboxen®) the potential regarding flow-electrochemistry has not been leveraged. Key developments for this are reproducible synthesis procedures to deposit active metal on the SPBCs and the design of an electrochemical flow cell using these catalysts in a fixed-bed electrode configuration.The first part of this work presents the deposition of Cu through different impregnation and reduction procedures on a SPBC (Carboxen® 1032, 50 µm, Merck). The carbon was characterized by physisorption, TPD-MS, TPO, Raman and SEM. The resulting metal-impregnated carbon catalysts were additionally investigated regarding the metal loading. Using the applied impregnation and reduction parameters targeted metal loadings (3 – 20 wt%) could be well achieved. The second part focuses on the design and commissioning of a flow-cell for the application of the SPBC-supported catalysts as a fixed-bed at the cathode side. Electrochemical synthesis reactions are targeted in the cell and the reduction of 5-HMF to BHMF was chosen as the test reaction in this work. In the framework of the cell development multiple aspects not only regarding the construction but also reaction engineering issues had to be considered: material stability of the pump, fixation and pressure drop of catalyst bed, choice of electrolyte, effect of dissolved oxygen in the catholyte, optimal flow rate, reliable electrochemical protocol and selection of contact material. The latter has to be a compromise between chemical inertness and an enhanced electron transfer between the catalyst bed and the contact material (e.g. soft foil vs. hard metal). Figure 1A shows the current voltage characteristics of two possible contact materials (graphite foil, boron-doped diamond (BDD)) in the targeted electrolyte (0.5M borate buffer with 0.25M potassium chloride). Here, the graphite foil clearly shows a higher activity towards the hydrogen evolution reaction which may result in a less effective electrolysis later on. The comparison of BDD as contact material without and with a catalyst bed (Carboxen® 1032 loaded with 20 wt% Cu) resulted in a significant shift in the current voltage characteristic to lower overpotentials. Therefore, the electronic contact with the carbon bed is clearly enabled and the carbon spheres loaded with copper catalyze the reaction. Figure 1B presents the results of the test reaction with the conversion of the educt 5-HMF as well as the selectivity to the targeted product BHMF over the reaction time with BDD as contact material without and with a fixed bed of Cu/SPBC catalyst. The experiments prove full 5-HMF conversion within 23 h on stream in combination with a high selectivity towards BHMF with the catalyst bed. The mass-based productivity reaches values of up to 1.78 mmol h-1 gCu -1 and is therefore about 15 times higher compared to the use of conventional Cu foil (Pliterature = 0.11 mmol h-1 gCu -1 [6]). It is possible that due to the metal-support approach in the fixed-bed configuration, the copper is leveraged more efficiently and small amounts allow to provide sufficient metal surface area for the catalytic reaction.

A novel photoreduction deposition induced AuNPs/COFs composite for SERS detection of macrolide antibiotics

As we all know, SERS (Surface-enhanced Raman spectroscopy) is widely used in sensing, analysis and detection. The covalent organic frameworks (COFs) have performed well as a material for supporting metal nanoparticles and facilitating analyte adsorption in SERS, which may greatly enhance the detection sensitivity and reproducibility. The synthesis of traditional metal/COFs composites involved chemical reduction methods, however, the resulting metallic NPs exhibited reduced capacity to enhance SERS due to their small particle sizes (usually <20 nm). This paper presented a novel photoreduction method for the facile growth of AuNPs (diameters: 75 nm) on COFs matrix under light control, which represents the first report of such synthesis on COF. Subsequently, the photoreduction deposition induced AuNPs/COFs composites, which served as highly sensitive and reproducible SERS-active substrates for capturing the spectral information of four types of macrolide antibiotics. The detection limits for the four macrolide antibiotics were determined to be 3.30 × 10−11, 3.43 × 10−10, 1.10 × 10−10 and 5.78 × 10−11 M, respectively, exhibiting excellent linear relationships within the concentration range of 10−10 to 10−3 M. Therefore, our proposed SERS method opens up a new idea for the development of SERS substrates and environmental safety monitoring, and it has great potential for ensuring food safety in the future.

Rutile TiO2-Supported Pt Nanoparticle Catalysts for the Low-Temperature Oxidation of Ethane to Ethanol.

Structure-function relationships of supported metal nanoparticle catalysts in the CO-assisted oxidation of ethane to ethanol were investigated. A rutile TiO2-supported Pt nanoparticle catalyst exhibited the highest ethanol production rate and selectivity. During the reaction, sequential changes in the geometric/electronic states and the particle size of the Pt nanoparticles were observed. The comparison of the catalytic performances of model catalysts with controlled metal-support interactions revealed that Pt0 nanoparticles of 2-3 nm with a high fraction of the surface Ptδ+ species are highly active for the oxidation of ethane to ethanol. The coadded CO plays a pivotal role not only in tuning the oxidation state of the surface Pt but also in producing H2O2, which is the true oxidant for the reaction. The supported Pt nanoparticle uses in situ-generated H2O2 to activate ethane, where the C2H5OOH intermediate is formed through a nonradical mechanism and subsequently converted to C2H5OH. This reaction occurs even at 50 °C with an apparent activation energy of 32 kJ mol-1. The present study sheds light on the usefulness of surface-engineered Pt nanoparticles for the low-temperature oxidation of ethane to ethanol.

Tailoring Catalysis of Encapsulated Pt Nanoparticles by Pore Wall Engineering of Covalent Organic Frameworks

While supported metal nanoparticles (NPs) have shown significant promise in heterogeneous catalysis, precise control over their interaction with the support, which profoundly impacts their catalytic performance, remains a significant challenge. In this study, Pt NPs are incorporated into thioether‐functionalized covalent organic frameworks (denoted COF‐Sx), enabling precise control over the size and electronic state of Pt NPs by adjusting the thioether density dangling on the COF pore walls. Notably, the resulting Pt@COF‐Sx demonstrate exceptional selectivity (&gt;99%) in catalytic hydrogenation of p‐chloronitrobenzene to p‐chloroaniline, in sharp contrast to the poor selectivity of Pt NPs embedded in thioether‐free COFs. Furthermore, the conversion over Pt@COF‐Sx exhibits a volcano‐type curve as the thioether density increases, due to the corresponding change of accessible Pt sites. This work provides an effective approach to regulating the catalysis of metal NPs via their microenvironment modulation, with the aid of rational design and precise tailoring of support structure.

Tailoring Catalysis of Encapsulated Platinum Nanoparticles by Pore Wall Engineering of Covalent Organic Frameworks.

While supported metal nanoparticles (NPs) have shown significant promise in heterogeneous catalysis, precise control over their interaction with the support, which profoundly impacts their catalytic performance, remains a significant challenge. In this study, Pt NPs are incorporated into thioether-functionalized covalent organic frameworks (denoted COF-Sx), enabling precise control over the size and electronic state of Pt NPs by adjusting the thioether density dangling on the COF pore walls. Notably, the resulting Pt@COF-Sx demonstrate exceptional selectivity (> 99 %) in catalytic hydrogenation of p-chloronitrobenzene to p-chloroaniline, in sharp contrast to the poor selectivity of Pt NPs embedded in thioether-free COFs. Furthermore, the conversion over Pt@COF-Sx exhibits a volcano-type curve as the thioether density increases, due to the corresponding change of accessible Pt sites. This work provides an effective approach to regulating the catalysis of metal NPs via their microenvironment modulation, with the aid of rational design and precise tailoring of support structure.

Wood-Structured Nanomaterials as Highly Efficient, Self-Standing Electrocatalysts for Water Splitting.

Electrocatalytic water splitting (EWS) driven by renewable energy is widely considered an environmentally friendly and sustainable approach for generating hydrogen (H2), an ideal energy carrier for the future. However, the efficiency and economic viability of large-scale water electrolysis depend on electrocatalysts that can efficiently accelerate the electrochemical reactions taking place at the two electrodes. Wood-derived nanomaterials are well-suited for serving as EWS catalysts because of their hierarchically porous structure with high surface area and low tortuosity, compositional tunability, cost-effectiveness, and self-standing integral electrode configuration. Here, recent advancements in the design and synthesis of wood-structured nanomaterials serving as advanced electrocatalysts for water splitting are summarized. First, the design principles and corresponding strategies toward highly effective wood-structured electrocatalysts (WSECs) are emphasized. Then, a comprehensive overview of current findings on WSECs, encompassing diverse structural designs and functionalities such as supported-metal nanoparticles (NPs), single-atom catalysts (SACs), metal compounds, and heterostructured electrocatalysts based on engineered wood hosts are presented. Subsequently, the application of these WSECs in various aspects of water splitting, including the hydrogen evolution reaction (HER), oxygen evolution reaction (OER), overall water splitting (OWS), and hybrid water electrolysis (HWE) are explored. Finally, the prospects, challenges, and opportunities associated with the broad application of WSECs are briefly discussed. This review aims to provide a comprehensive understanding of the ongoing developments in water-splitting catalysts, along with outlining design principles for the future development of WSECs.

Scaling-Up Microwave-Assisted Synthesis of Highly Defective Pd@UiO-66-NH2 Catalysts for Selective Olefin Hydrogenation under Ambient Conditions.

The need to develop green and cost-effective industrial catalytic processes has led to growing interest in preparing more robust, efficient, and selective heterogeneous catalysts at a large scale. In this regard, microwave-assisted synthesis is a fast method for fabricating heterogeneous catalysts (including metal oxides, zeolites, metal-organic frameworks, and supported metal nanoparticles) with enhanced catalytic properties, enabling synthesis scale-up. Herein, the synthesis of nanosized UiO-66-NH2 was optimized via a microwave-assisted hydrothermal method to obtain defective matrices essential for the stabilization of metal nanoparticles, promoting catalytically active sites for hydrogenation reactions (760 kg·m-3·day-1 space time yield, STY). Then, this protocol was scaled up in a multimodal microwave reactor, reaching 86% yield (ca. 1 g, 1450 kg·m-3·day-1 STY) in only 30 min. Afterward, Pd nanoparticles were formed in situ decorating the nanoMOF by an effective and fast microwave-assisted hydrothermal method, resulting in the formation of Pd@UiO-66-NH2 composites. Both the localization and oxidation states of Pd nanoparticles (NPs) in the MOF were achieved using high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and X-ray photoelectron spectroscopy (XPS), respectively. The optimal composite, loaded with 1.7 wt % Pd, exhibited an extraordinary catalytic activity (>95% yield, 100% selectivity) under mild conditions (1 bar H2, 25 °C, 1 h reaction time), not only in the selective hydrogenation of a variety of single alkenes (1-hexene, 1-octene, 1-tridecene, cyclohexene, and tetraphenyl ethylene) but also in the conversion of a complex mixture of alkenes (i.e., 1-hexene, 1-tridecene, and anethole). The results showed a powerful interaction and synergy between the active phase (Pd NPs) and the catalytic porous scaffold (UiO-66-NH2), which are essential for the selectivity and recyclability.

Highly Active and Sintering-Resistant Pt Clusters Supported on FeOx-Hydroxyapatite Achieved by Tailoring Strong Metal-Support Interactions.

The catalytic performance of supported metal catalysts is closely related to their structure. While Pt-based catalysts are widely used in many catalytic reactions because of their exceptional intrinsic activity, they tend to deactivate in high-temperature reactions, requiring a tedious and expensive regeneration process. The strong metal-support interaction (SMSI) is a promising strategy to improve the stability of supported metal nanoparticles, but often at the price of the activity due to either the coverage of the active sites by support overlay and/or the too-strong metal-support bonding. Herein, we newly constructed a supported Pt cluster catalyst by introducing FeOx into hydroxyapatite (HAP) support to fine-tune the SMSIs. The catalyst exhibited not only high catalytic activity but also sintering resistance, without deactivation in a 100 h test for catalytic CO oxidation. Detailed characterizations reveal that FeOx introduced into HAP weaken the strong covalent metal-support interaction (CMSI) between Pt and FeOx while simultaneously inhibiting the oxidative strong metal-support interaction (OMSI) between Pt and HAP, giving rise to both high activity and thermal stability of the supported Pt clusters.

Design Strategy of Metal Nanoparticle Catalysis for C−H Bond Activation Reactions

AbstractC−H bond activation reactions facilitate highly efficient molecular transformations without requiring pre‐activating substrates. While the majority of reported reaction systems for C−H activation rely on metal complexes, certain reactions have demonstrated unique or superior catalysis of metal nanoparticles. This Concept article seeks to delineate recent reports that examine the novel catalysis and design strategy of supported metal nanoparticles for C−H bond activation reactions. These reactions include oxidative homocoupling of arenes, dehydrogenative alkylation of benzenes, selective H/D exchange reactions, and α,β‐dehydrogenation of ketones.

Carbon-dot liposome–based synthesis of gold nanocatalysts for efficient reduction of 4-nitrophenol in wastewater

Supported metal nanoparticles (NPs) having high catalytic activity and stability hold great promise in many fields including catalytic wastewater treatment. These NPs can be effectively stabilized by the suitable carriers to achieve satisfactory long-term stability and increased recyclability. Compared with common solid-state supports, catalyst supports with dynamic behavior are expected to endow active sites with additional degrees of freedom for enhanced catalytic performance. Here, a novel dynamical nanocatalyst support utilizing lamellar vesicles formed via self-assembly of lipid-like carbon dots was devised for in situ growth of gold NPs decorated carbon-dot liposomes (AuNPs@CDLs) in catalytic reduction application. CDLs with abundant carbon domains and surface functional groups are ideal hosts for carrying high-density Au NPs, which are beneficial for providing large number of active sites. CDLs also endow high substrate entrapment and adsorption capacity and thereby improve the overall catalytic performance. Our results reveal that AuNPs@CDLs exhibited superior catalytic activity than unsupported Au NPs for catalytic reduction of 4-nitrophenol (4-NP) with sodium borohydride. The increased fluidity in the vesicle membrane also leads to an enhancement of catalytic efficiency. AuNPs@CDLs have been successfully applied in industrial wastewater treatment, with results of almost complete degradation of 4-NP within 3 min. As a dynamically self-assembled support, CDLs can not only improve the stability against salt-induced aggregation and reusability of immobilized metal nanocatalysts, but also enhance the accessibility of active sites through the intrinsic fluidity of vesicle membranes.

Distribution of Pt single atom coordination environments on anatase TiO2 supports controls reactivity

Single-atom catalysts (SACs) offer efficient metal utilization and distinct reactivity compared to supported metal nanoparticles. Structure-function relationships for SACs often assume that active sites have uniform coordination environments at particular binding sites on support surfaces. Here, we investigate the distribution of coordination environments of Pt SAs dispersed on shape-controlled anatase TiO2 supports specifically exposing (001) and (101) surfaces. Pt SAs on (101) are found on the surface, consistent with existing structural models, whereas those on (001) are beneath the surface after calcination. Pt SAs under (001) surfaces exhibit lower reactivity for CO oxidation than those on (101) surfaces due to their limited accessibility to gas phase species. Pt SAs deposited on commercial-TiO2 are found both at the surface and in the bulk, posing challenges to structure-function relationship development. This study highlights heterogeneity in SA coordination environments on oxide supports, emphasizing a previously overlooked consideration in the design of SACs.

Correction: Microwave facile preparation of highly active and dispersed SBA-12 supported metal nanoparticles

Correction for ‘Microwave facile preparation of highly active and dispersed SBA-12 supported metal nanoparticles’ by Juan Manuel Campelo et al., Green Chem., 2008, 10, 853–858, https://doi.org/10.1039/B801754A.

Metal–organic framework-derived hierarchical porous N/Co-doped carbon-supported sponge-like Pd–SnO2 nanostructures for low-temperature CO oxidation

Metal–organic framework-derived porous N/Co-doped carbon (MOF-PNC) anchored sponge-like Pd–SnO2 nanoparticles (Pd–SnO2/MOF-PNC), prepared by microwave-irradiation, annealing and chemical etching, delivered excellent low-temperature carbon monoxide oxidation.

Immobilization of biogenic metal nanoparticles on sustainable materials – green approach applied to wastewater treatment: a systematic review

The simultaneous use of bio-resources and sustainable materials as reducing/capping agents and supporting materials to obtain supported metal nanoparticles is a significant green approach applied to wastewater treatment.