Supported Metal Nanoparticles Research Articles

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.

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 (>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 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 (>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.

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.

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.

Supported Metal Nanoparticles‐Based Catalysts and their Interactions with H2: Insights from Inelastic Neutron Scattering Spectroscopy

AbstractThe investigation of supported metal nanoparticle in the presence of H2 is fundamental to better understand their behavior as hydrogenation catalysts. In this respect, this review will focus on the main recent results obtained by Inelastic Neutron Scattering (INS) spectroscopy, which is of particular interest thanks to its ability to provide very detailed vibrational spectra of the H‐containing species in the sample. The review will cover the main results concerning the characterization of the H‐species already present in the pristine catalyst, with a particular focus on carbon‐based materials and their modification upon the interaction with metal nanoparticles. Successively, the forms in which H2 interacts with the catalysts will be examined, starting from H2 physisorption, to then pass to the metal hydride species formed through the splitting of dihydrogen upon the active metallic phase, and finally to the migration of atomic hydrogen from the metal nanoparticles onto the support as a result of hydrogen spillover. The aim of the review is to present an overview of all the hydrogenous species identifiable by INS spectroscopy in hydrogenation catalysts, focusing on the specific case of supported metal nanoparticles systems.

H2[Pt(C2O4)2] as a Tailor‐made Halide‐free Precursor for the Preparation of Diesel Oxidation Catalysts: Nanoparticles Formation, Thermal Stability and Catalytic Performance

AbstractThe aim of this study was to investigate a tailor‐made metal precursor and its chemical properties to tune the properties of supported metal nanoparticles (NPs) and their catalytic performance when used as Diesel Oxidation Catalyst (DOC). The formation of extremely small Pt NPs from a new halide‐free Pt complex was investigated, namely bis(oxalato)platinate, H2[Pt(C2O4)2]. The size evolution of the supported NPs, from the formation upon the Pt precursor decomposition on γ‐alumina to the sintering of the NPs at high temperatures, was followed by thermogravimetric analysis coupled with mass spectrometry (TG‐MS) and differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy. A correlation between the NPs’ size of the catalyst and the performance for the CO, C3H6, C3H8 and NO oxidation reactions pointed out a retained activity during test cycles, showing low sensitivity to the test conditions applied (i. e., temperature and gas composition). The overall catalytic performance was better in the fresh catalysts compared to the reference catalyst prepared from platinum nitrate, Pt(NO3)4. In particular, the different dispersion of the Pt NPs over the support obtained from the two precursors was identified as the reason for the different catalytic performance, retaining small NPs size after the tests cycles.

Atomic-Scale 3D Structure of a Supported Pd Nanoparticle Revealed by Electron Tomography with Convolution Neural Network-Based Image Inpainting.

Electron tomography based on scanning transmission electron microscopy (STEM) is used to analyze 3D structures of metal nanoparticles on the atomic scale. However, in the case of supported metal nanoparticle catalysts, the supporting material may interfere with the 3D reconstruction of metal nanoparticles. In this study, a deep learning-based image inpainting method is applied to high-angle annular dark field (HAADF)-STEM images of a supported metal nanoparticle to predict and remove the background image of the support. The inpainting method can separate an 11nm Pd nanoparticle from the θ-Al2 O3 support in HAADF-STEM images of the θ-Al2 O3 -supported Pd catalyst. 3D reconstruction of the extracted images of the Pd nanoparticle reveals that the Pd nanoparticle adopts a deformed structure of the cuboctahedron model particle, resulting in high index surfaces, which account for the high catalytic activity for methane combustion. Using the xyz coordinate of each Pd atom, the local Pd-Pd bond distance and its variance in a real supported Pd nanoparticle are visualized, showing large strain and disorder at the Pd-Al2 O3 interface. The results demonstrate that 3D atomic-scale analysis enables atomic structure-based understanding and design of supported metal catalysts.

Nanoarchitectonics and catalytic performances of metal–organic frameworks supported metal nanoparticles

Metal–organic frameworks (MOFs) supported metal nanoparticles (MNPs) (MNPs@MOFs) composites, as a class of effective functional materials, have been extensively explored because of the synergetic effect of MOFs and MNPs. Lots of synthesized methods are developed to synthesize MNPs@MOFs composites. These strategies can be generally divided into four main synthesis strategies: ship‐in‐the‐bottle, bottle‐around‐the‐ship, one‐pot, and sandwich assembly approaches. In this review, the recent synthesized strategies are discussed and summarized for the design and fabrication of different MNPs@MOFs composites. Then, the catalytic applications of some MNPs@MOFs composites are presented. Lastly, the challenges and future perspectives are also pointed out in this hot research filed.

Significant Roles of Surface Hydrides in Enhancing the Performance of Cu/BaTiO2.8H0.2 Catalyst for CO2 Hydrogenation to Methanol

AbstractTuning the anionic site of catalyst supports can impact reaction pathways by creating active sites on the support or influencing metal‐support interactions when using supported metal nanoparticles. This study focuses on CO2 hydrogenation over supported Cu nanoparticles, revealing a 3‐fold increase in methanol yield when replacing oxygen anions with hydrides in the perovskite support (Cu/BaTiO2.8H0.2 yields ~146 mg/h/gCu vs. Cu/BaTiO3 yields ~50 mg/h/gCu). The contrast suggests that significant roles are played by the support hydrides in the reaction. Temperature programmed reaction and isotopic labelling studies indicate that BaTiO2.8H0.2 surface hydride species follow a Mars van Krevelen mechanism in CO2 hydrogenation, promoting methanol production. High‐pressure steady‐state isotopic transient kinetic analysis (SSITKA) studies suggest that Cu/BaTiO2.8H0.2 possesses both a higher density and more active and selective sites for methanol production compared to Cu/BaTiO3. An operando high‐pressure diffuse reflectance infrared spectroscopy (DRIFTS)‐SSITKA study shows that formate species are the major surface intermediates over both catalysts, and the subsequent hydrogenation steps of formate are likely rate‐limiting. However, the catalytic reactivity of Cu/BaTiO2.8H0.2 towards the formate species is much higher than Cu/BaTiO3, likely due to the altered electronic structure of interface Cu sites by the hydrides in the support as validated by density functional theory (DFT) calculations.

Significant Roles of Surface Hydrides in Enhancing the Performance of Cu/BaTiO2.8 H0.2 Catalyst for CO2 Hydrogenation to Methanol.

Tuning the anionic site of catalyst supports can impact reaction pathways by creating active sites on the support or influencing metal-support interactions when using supported metal nanoparticles. This study focuses on CO2 hydrogenation over supported Cu nanoparticles, revealing a 3-fold increase in methanol yield when replacing oxygen anions with hydrides in the perovskite support (Cu/BaTiO2.8 H0.2 yields ~146 mg/h/gCu vs. Cu/BaTiO3 yields ~50 mg/h/gCu). The contrast suggests that significant roles are played by the support hydrides in the reaction. Temperature programmed reaction and isotopic labelling studies indicate that BaTiO2.8 H0.2 surface hydride species follow a Mars van Krevelen mechanism in CO2 hydrogenation, promoting methanol production. High-pressure steady-state isotopic transient kinetic analysis (SSITKA) studies suggest that Cu/BaTiO2.8 H0.2 possesses both a higher density and more active and selective sites for methanol production compared to Cu/BaTiO3 . An operando high-pressure diffuse reflectance infrared spectroscopy (DRIFTS)-SSITKA study shows that formate species are the major surface intermediates over both catalysts, and the subsequent hydrogenation steps of formate are likely rate-limiting. However, the catalytic reactivity of Cu/BaTiO2.8 H0.2 towards the formate species is much higher than Cu/BaTiO3 , likely due to the altered electronic structure of interface Cu sites by the hydrides in the support as validated by density functional theory (DFT) calculations.