AuPd Nanoparticles Research Articles

Accelerated Deactivation of Mesoporous Co3O4-Supported Au–Pd Catalyst through Gas Sensor Operation

High activity of a catalyst and its thermal stability over a lifetime are essential for catalytic applications, including catalytic gas sensors. Highly porous materials are attractive to support metal catalysts because they can carry a large quantity of well-dispersed metal nanoparticles, which are well-accessible for reactants. The present work investigates the long-term stability of mesoporous Co3O4-supported Au–Pd catalyst (Au–Pd@meso-Co3O4), with a metal loading of 7.5 wt% and catalytically active mesoporous Co3O4 (meso-Co3O4) for use in catalytic gas sensors. Both catalysts were characterized concerning their sensor response towards different concentrations of methane and propane (0.05–1%) at operating temperatures ranging from 200 °C to 400 °C for a duration of 400 h. The initially high sensor response of Au–Pd@meso-Co3O4 to methane and propane decreased significantly after a long-term operation, while the sensor response of meso-Co3O4 without metallic catalyst was less affected. Electron microscopy studies revealed that the hollow mesoporous structure of the Co3O4 support is lost in the presence of Au–Pd particles. Additionally, Ostwald ripening of Au–Pd nanoparticles was observed. The morphology of pure meso-Co3O4 was less altered. The low thermodynamical stability of mesoporous structure and low phase transformation temperature of Co3O4, as well as high metal loading, are parameters influencing the accelerated sintering and deactivation of Au–Pd@meso-Co3O4 catalyst. Despite its high catalytic activity, Au–Pd@meso-Co3O4 is not long-term stable at increased operating temperatures and is thus not well-suited for gas sensors.

Acetylene functionalized covalent triazine frameworks with AuPd nanoparticles as photocatalysts for hydrogen evolution from formic acid

Photocatalytic dehydrogenation of formic acid (FA) at room temperature is a promising way to meet the increasing demand for hydrogen energy. In this work, we loaded nanoparticles of plasmonic AuPd alloys on the acetylene functionalized covalent triazine frameworks (CTFs) for the design of Mott-Schottky catalysts (AuPd/CTFs) with further application to photocatalytic hydrogen production from FA. Experimental data showed that the introduction of acetylene (-C≡C-) unit and AuPd alloy into the CTF could significantly enhance the performance of hydrogen evolution. The results of photoelectrochemical tests showed that the introduction of carbon-carbon triple bonds and AuPd alloy could adjust the electronic structure of CTF and inhibit charge recombination. Thus, benefiting from these positive effects, the FA photocatalytic decomposition by the obtained AuPd-CTF-EDDBN photocatalyst yielded H2 at a good rate of 10600 μmol·gcat −1·h−1.

Bimetallic (AuAg, AuPd and AgPd) nanoparticles supported on cellulose-based hydrogel for reusable catalysis

Biopolymer-derived hydrogels with low-cost and sustainable features have been considered as fascinating supported materials for metal nanoparticles. Cellulose, as the most abundant biopolymer, is a renewable raw material to prepare biopolymer-derived hydrogels for catalysis. Here, a cellulose-based hydrogel is designed to load bimetallic (AuAg, AuPd and AgPd) nanoparticles. 4-Nitrophenol reduction and Suzuki–Miyaura coupling reactions are selected to evaluate and compare the catalytic performance of the resulting bimetallic nanoparticle-loaded cellulose-based composite hydrogels. The bimetallic nanocomposite hydrogels are easy to be recycled over 10 times during the catalytic experiments and possess good applicability and generality for various substrates. The catalytic activity of bimetallic nanocomposite hydrogels was compared with recent literatures. In addition, the possible catalytic mechanism is also proposed. This work is expected to give a new insight for designing and preparing bimetallic nanoparticle-based cellulose hydrogels and proves its applicability and prospect in the catalytic field.

AuPd Nanocatalysts Supported on Citric Acid-Modified Boron Nitride to Boost Hydrogen Generation from Formic Acid Dehydrogenation

Formic acid (FA) dehydrogenation is a potential technology for sustainable hydrogen production, while the tardy nature of FA dehydrogenation inhibits its development. To optimize the catalytic activity of hydrogen generation from formic acid dehydrogenation, citric acid-modified boron nitride with abundant −NH2 (CA–BN-NH2) is employed as a support to control the particle distribution, particle size, and electronic structure of AuPd nanoparticles. The obtained Au0.3Pd0.7/CA–BN-NH2 exhibits extraordinary catalytic activity for hydrogen production from FA dehydrogenation, possessing 100% hydrogen selectivity and an unprecedented initial turnover frequency (TOF) of 7046 mol H2 mol catalyst–1 h–1 without any additive, outperforming most of the reported noble metal catalysts under similar conditions. Transmission electron microscopy (TEM) images, X-ray photoelectron spectroscopy (XPS) analysis, and density functional theory (DFT) calculations demonstrate that the extraordinary catalytic activities are mainly due to the geometric effect and electronic effect of AuPd nanoparticles derived from the modification of h-BN with citric acid and the accompanying −NH2. This work provides more flexibility for designing highly efficient nanocatalysts for hydrogen generation from FA dehydrogenation.

MoS2 Nanoplatelets on Hybrid Core-Shell (HyCoS) AuPd NPs for Hybrid SERS Platform for Detection of R6G

In this work, a novel hybrid SERS platform incorporating hybrid core-shell (HyCoS) AuPd nanoparticles (NPs) and MoS2 nanoplatelets has been successfully demonstrated for strong surface-enhanced Raman spectroscopy (SERS) enhancement of Rhodamine 6G (R6G). A significantly improved SERS signal of R6G is observed on the hybrid SERS platform by adapting both electromagnetic mechanism (EM) and chemical mechanism (CM) in a single platform. The EM enhancement originates from the unique plasmonic HyCoS AuPd NP template fabricated by the modified droplet epitaxy, which exhibits strong plasmon excitation of hotspots at the nanogaps of metallic NPs and abundant generation of electric fields by localized surface plasmon resonance (LSPR). Superior LSPR results from the coupling of distinctive AuPd core-shell NP and high-density background Au NPs. The CM enhancement is associated with the charge transfer from the MoS2 nanoplatelets to the R6G. The direct contact via mixing approach with optimal mixing ratio can effectively facilitate the charges transfer to the HOMO and LUMO of R6G, leading to the orders of Raman signal amplification. The enhancement factor (EF) for the proposed hybrid platform reaches ~1010 for R6G on the hybrid SERS platform.

Mechanistic Studies into the Selective Production of 2,5-furandicarboxylic Acid from 2,5-bis(hydroxymethyl)furan Using Au-Pd Bimetallic Catalyst Supported on Nitrated Carbon Material

Aerobic oxidation of bio-sourced 2,5-bis(hydroxymethyl)furan (BHMF) to 2, 5-furandicarboxylic acid (FDCA), a renewable and green alternative to petroleum-derived terephthalic acid (TPA), is of great significance in green chemicals production. Herein, hierarchical porous bowl-like nitrogen-rich (nitrated) carbon-supported bimetallic Au-Pd nanocatalysts (AumPdn/ N-BNxC) with different nitrogen content and bimetal nanoparticle sizes were developed and employed for the highly efficient aerobic oxidation of BHMF to FDCA in sodium carbonate aqueous solution. The reaction pathway for catalytic oxidation of BHMF went through the steps of BHMF→HMF→HMFCA→FFCA→FDCA. Kinetics studies showed that the activation energies of BHMF, HMF, HMFCA, and FFCA were 58.1 kJ·moL−1, 39.1 kJ·moL−1, 129.2 kJ·moL−1, and 56.3 kJ·moL−1, respectively, indicating that the oxidation of intermediate HMFCA to FFCA was the rate-determining step. ESR tests proved that the active species was a superoxide radical. Owing to the synergy between the nitrogen-rich carbon support and bimetallic Au-Pd nanoparticles, the Au1Pd1/N-BN2C nanocatalysts exhibited BHMF conversion of 100% and FDCA yield of 95.8% under optimal reaction conditions. Furthermore, the nanocatalysts showed good stability and reusability. This work provides a versatile strategy for the design of heterogeneous catalysts for the highly efficient production of FDCA from BHMF.

Hierarchical Flower-like WO3 Nanospheres Decorated with Bimetallic Au and Pd for Highly Sensitive and Selective Detection of 3-Hydroxy-2-butanone Biomarker.

Listeria monocytogenes, which is abundant in environment, can lead to many kinds of serious illnesses and even death. Nowadays, indirectly detecting the metabolite biomarker of L. monocytogenes, 3-hydroxy-2-butanone, has been verified to be an effective way to evaluate the contamination of L. monocytogenes. However, this detection approach is still limited by sensitivity, selectivity, and ppb-level detection limit. Herein, low-cost and highly sensitive and selective 3-hydroxy-2-butanone sensors have been proposed based on the bimetallic AuPd decorated hierarchical flower-like WO3 nanospheres. Notably, the 1.0 wt % AuPd-WO3 based sensors displayed the highest sensitivity (Ra/Rg = 84 @ 1 ppm) at 250 °C. In addition, the sensors showed outstanding selectivity, rapid response/recovery (8/4 s @ 10 ppm), and low detection limit (100 ppb). Furthermore, the evaluation of L. monocytogenes with high sensitivity and specificity has been achieved using 1.0 wt % AuPd-WO3 based sensors. Such a marvelous sensing performance benefits from the synergistic effect of bimetallic AuPd nanoparticles, which lead to thicker electron depletion layer and increased adsorbed oxygen species. Meanwhile, the unique hierarchical nanostructure of the flower-like WO3 nanospheres benefits the gas-sensing performance. The AuPd-WO3 nanosphere-based sensors exhibit a particular and highly selective method to detect 3-hydroxy-2-butanone, foreseeing a feasible route for the rapid and nondestructive evaluation of foodborne pathogens.

Transport Mediating Core-Shell Photocatalyst Architecture for Selective Alkane Oxidation.

The high activation barrier of the C-H bond in methane, combined with the high propensity of methanol and other liquid oxygenates toward overoxidation to CO2, have historically posed significant scientific and industrial challenges to the selective and direct conversion of methane to energy-dense fuels and chemical feedstocks. Here, we report a unique core-shell nanostructured photocatalyst, silica encapsulated TiO2 decorated with AuPd nanoparticles (TiO2@SiO2-AuPd), that prevents methanol overoxidation on its surface and possesses high selectivity and yield of oxygenates even at high UV intensity. This room-temperature approach achieves high selectivity for oxygenates (94.5%) with a total oxygenate yield of 15.4 mmol/gcat·h at 9.65 bar total pressure of CH4 and O2. The working principles of this core-shell photocatalyst were also systematically investigated. This design concept was further demonstrated to be generalizable for the selective oxidation of other alkanes.

Demystifying the Chemical Ordering of Multimetallic Nanoparticles

ConspectusMultimetallic nanoparticles (NPs) have highly tunable properties due to the synergy between the different metals and the wide variety of NP structural parameters such as size, shape, composition, and chemical ordering. The major problem with studying multimetallic NPs is that as the number of different metals increases, the number of possible chemical orderings (placements of different metals) for a NP of fixed size explodes. Thus, it becomes infeasible to explore NP energetic differences with highly accurate computational methods, such as density functional theory (DFT), which has a high computational cost and is typically applied to up to a couple of hundred metal atoms. Here, we demonstrate a methodology advancing NP simulations by effectively exploring the vast materials space of multimetallic NPs and accurately identifying the ones with the most thermodynamically preferred chemical orderings. With accuracies reaching that of DFT, our methodology is applicable to practically any NP size, shape, and metal composition. We achieve this by significantly advancing the bond-centric (BC) model, a physics-based model that has been previously shown to rapidly predict bimetallic NP cohesive energies (CEs). Specifically, the BC model is trained in a way to understand how the bimetallic bond strength changes under different coordination environments present on a NP and how the metal composition of every site affects the detailed coordination environment using fractional coordination numbers. This newly modified BC model leads to an improvement from 0.331 (original model) to 0.089 eV/atom in CE predictions when compared to DFT values on a robust data set of 90 different NPs consisting of PtPd, AuPt, and AuPd NPs with varying compositions and chemical orderings. By incorporating the modified BC model into an in-house-developed genetic algorithm (GA) we can effectively and accurately predict the most stable chemical orderings of large, realistic bimetallic NPs consisting of thousands of metal atoms. This is demonstrated on AuPd bimetallic NPs, a challenging system due to the similarity in the cohesion of the two metals. By training our BC model using a unique DFT calculation on a bimetallic NP (one calculation for two metals combining together), we expand to explore the chemical ordering of multimetallic NPs. We first demonstrate the application of our methodology on a AuPdPt NP and validate our stability predictions with literature data. Then, we effectively explore the vast materials space of multimetallic NPs consisting of combinations of Au, Pt, and Pd as a function of metal composition. Our thermodynamic stability trends are presented in a ternary diagram revealing detailed, and yet, unexpected chemical ordering trends. Our computational framework can aid both experimental and computational researchers toward effectively screening multimetallic NP stability. Moreover, we provide an outlook of how this framework can be applied to catalyst discovery, high-entropy alloys, and single-atom alloys.

Decarbonylation of 1,2-Diketones Catalyzed by Au–Pd Nanoparticles Supported on CeO2

Decarbonylation of 1,2-Diketones Catalyzed by Au–Pd Nanoparticles Supported on CeO2

In Cellulo Bioorthogonal Catalysis by Encapsulated AuPd Nanoalloys: Overcoming Intracellular Deactivation.

Bioorthogonal metallocatalysis has opened up a xenobiotic route to perform nonenzymatic catalytic transformations in living settings. Despite their promising features, most metals are deactivated inside cells by a myriad of reactive biomolecules, including biogenic thiols, thereby limiting the catalytic functioning of these abiotic reagents. Here we report the development of cytocompatible alloyed AuPd nanoparticles with the capacity to elicit bioorthogonal depropargylations with high efficiency in biological media. We also show that the intracellular catalytic performance of these nanoalloys is significantly enhanced by protecting them following two different encapsulation methods. Encapsulation in mesoporous silica nanorods resulted in augmented catalyst reactivity, whereas the use of a biodegradable PLGA matrix increased nanoalloy delivery across the cell membrane. The functional potential of encapsulated AuPd was demonstrated by releasing the potent chemotherapy drug paclitaxel inside cancer cells. Nanoalloy encapsulation provides a novel methodology to develop nanoreactors capable of mediating new-to-life reactions in cells.

Amine Functionalization Within Hierarchically‐Porous Zeotype Framework for Plasmonic Catalysis over PdAu Nanoparticles

AbstractPlasmonic catalysis has revealed improved product yield and selectivity in various chemical transformation reactions over the past decade. In this report, the effect of tertiary amine (‐NR3) functionalization on the surface of hierarchically‐porous zeotype (HP‐AlPO‐5) materials to enhance the plasmon‐mediated catalysis, utilizing a combination of the plasmonic antenna (Au) and catalytic reactor (Pd) nanoparticles (NPs) was investigated. The catalysts have been characterized using enhanced techniques such as HAADF‐STEM, FT‐EXAFS, and probe‐based FT‐IR to reveal the proximity and interaction between bimetallic NPs, and thermal stability of amines in the presence of Au or PdAu NPs. Interestingly, a four‐fold enhancement in the Suzuki‐Miyaura coupling reaction product yield was obtained over PdAu/HP‐AlPO‐5‐NR3 when compared with the analogous plasmonic catalyst with no amine functionalization under visible light irradiation. A range of amines were functionalized and their influence in the nucleation, uniform growth and stabilization of catalytic active site (Pd) and formation of electron‐rich species under visible light irradiation has also been investigated. The presence of tertiary amine in the nanostructured catalyst enhanced the turnover number (TON) significantly under light irradiation conditions in comparison to dark conditions. This study provides an enriched understanding of plasmon‐driven chemistry, where the maximized reaction rate enhancement requires the existence of active metal species and the formation of electron‐enriched species under light irradiation conditions.

AuPd bimetallic functionalized monodisperse In2O3 porous spheres for ultrasensitive trimethylamine detection

The use of bimetallic nanoparticles (NPs) to enhance the performance of oxide semiconductor gas sensor is a promising approach. In this work, monodisperse In2O3 porous spheres were synthesized by a simple hydrothermal method, and bimetallic AuPd NPs were decorated on In2O3 nanospheres by in-situ redox reaction, then Au, Pd and AuPd-modified In2O3 were obtained. Characterization results of SEM and TEM showed that the as-synthesized materials had monodisperse porous sphere morphology with uniform diameter of within 300 nm. The gas sensing test results showed that AuPd-In2O3 sensor has excellent gas sensing performance, specifically, lower detection limit (300 ppb, 1.35), and an ultra-short response time (2 s), as well as a high response to 100 ppm trimethylamine (TMA) (Ra/Rg=367.0) which was 12, 127 and 334 times higher than that of Pd-In2O3 (Ra/Rg=30.3), Au-In2O3 (Ra/Rg=2.9) and pristine In2O3 (Ra/Rg=1.1). The gas sensor also has a good long-term stability, repeatability, and cross-selectivity. The mechanism of enhanced gas sensing performance was proposed combining with chemical sensitization of Au, electronic sensitization of Pd, and synergetic catalytic effect of AuPd bimetallic NPs. This work provides a promising material for the design and preparation of gas sensors for TMA detection.

Modulating the microenvironment of AuPd nanoparticles using metal–organic frameworks for selective methane oxidation

The AuPd nanoparticles incorporated into Cu2+-doped MOFs selectively oxidize CH4 to CH3OH with H2O2 as an oxidant. The Cu species can alter the CH3OH selectivity by modulating the AuPd electronic state to improve CH4 adsorption and regulating the ˙OH formation.

Tuning the surface properties of AuPd nanoparticles for adsorption of O and CO.

Bimetallic nanoparticles are attracting increasing attention as effective catalysts because they can exhibit higher efficiencies than their monometallic counterparts. Recent studies show that PdAu nanoparticles can exhibit truly impressive catalytic activity, due to the synergistic effect of their properties. However, fine-tuning the catalytic activity requires an understanding of the full picture of the processes taking place in bimetallic particles of different compositions and structures. Here we study the influence of the structure and composition of PdAu nanoparticles on their electronic properties, charge distribution and adsorption properties (CO and O) using ab initio calculations. Two types of nanoparticles were considered: core-shell (Pd@Au and Au@Pd) and bimetallic alloy (Au-Pd) with an average diameter of 2 nm (321 atoms), having either fcc, icosahedral or amorphous structures. The results obtained on surface charges show the possibility of fine-tuning the surface properties of nanoparticles by modifying their atomic structure and composition. In addition, the adsorption of O and CO on the surface of PdAu nanoparticles with fcc structure has been studied. The obtained adsorption data correlate with the surface charge redistribution and the d-band center. The results of this study thus open up great prospects for tuning the catalytic properties of nanocatalysts by modifying their local atomic environment.

Urethane functions can reduce metal salts under hydrothermal conditions: synthesis of noble metal nanoparticles on flexible sponges applied in semi-automated organic reduction.

We report an additive-free one-pot hydrothermal synthesis of Au, Ag, Pd, and alloy AuPd nanoparticles (NPs) anchored on commercial polyurethane (PU) foams. While unable to reduce the precursor metal salts at room temperature, PU is able to serve as a reducing agent under hydrothermal conditions. The resulting NP@PU sponge materials perform comparably to reported state-of-the-art reduction catalysts, and are additionally very well suited for use in semi-automated synthesis: the NP anchoring is strong enough and the support flexible enough to be used as a 'catalytic sponge' that can be manipulated with a robotic arm, i.e., be repeatedly dipped into and drawn out of solutions, wrung out, and re-soaked.

Efficient catalytic hydrogen generation from formic acid dehydrogenation on ultrafine PdAu nanoparticles supported on modified carbon derived from rice straw

Formic acid (FA) dehydrogenation at ambient conditions is a promising route for hydrogen (H2) generation but still suffers from low activity and selectivity. Here, potassium hydroxide (KOH) and 3-aminopropyl triethoxysilane (APTES) modified porous carbon derived from the pyrolysis of rice straw (RSNPC) offers an effective support to promote the formation of ultrafine PdAu nanoparticles (NPs). Benefiting from the small sizes of PdAu NPs, the Pd0.7Au0.3/RSNPC catalyst exhibits excellent catalytic performance for FA dehydrogenation reaction with a high turnover frequency (TOF) of 6794.3 mol H2 mol catalyst−1 h−1 at ambient conditions, outperforming most of reported catalysts for FA dehydrogenation under similar conditions.

Unravelling synergistic effects in bi-metallic catalysts: deceleration of palladium–gold nanoparticle coarsening in the hydrogenation of cinnamaldehyde

In this work, we demonstrate that the synergistic effect of PdAu nanoparticles (NPs) in hydrogenation reactions is not only related to high activity but also to their stability when compared to Pd mono-metallic NPs.

Polystyrene stabilized Pd-Au nanoalloy for efficient synthesis of bis(indolyl)methanes from aryl iodides using oxalic acid as CO and H2 source

Herein, first example of heterogeneously catalyzed carbonylative synthesis of bis(indolyl)methanes from aryl iodides in one-pot and single-step manner has been reported. The reaction was best catalyzed by polystyrene supported bimetallic Pd-Au (Pd-Au@PS) nanoparticles (NPs) in comparison to various supported monometallic Pd-catalysts. The key feature of this protocol involves the application of oxalic acid as economic, solid, and safe multi-functional reagent which acts as a CO, H2 source as well as acid co-catalyst with PEG-200 as green solvent reaction medium for delivering moderate to excellent yields of the desired products, bis(indolyl)methanes (BIMs). The developed protocol is additive, phosphine ligand-free under air/moisture stable recyclable catalyst bearing easy accessibility/affordability to starting materials.

Mild and Rapid Light-Driven Suzuki-Miyaura Reactions Catalyzed by AuPd Nanoparticles in Water at Room Temperature.

Organic reactions carried out in water under mild conditions are state-of-the-art in terms of environmentally benign chemical processes. In this direction, plasmonic catalysis can aid in accomplishing such tasks. In the present work, cyclodextrin-mediated AuPd bimetallic nanoparticles (NPs) were applied in room-temperature aqueous Suzuki-Miyaura reactions aiming at preparing biaryl products based on fluorene, isatin, benzimidazole and resorcinol, with yields of 77 % up to 95 %. AuPd NPs were revealed to be a physical mixture of Au and Pd particles circa 20 and 2 nm, respectively, through X-ray diffraction, dynamic light scattering, UV-Vis spectroscopy and transmission electron microscopy analyses.