Au Pd Bimetallic Nanoparticles Research Articles

Synthesis and catalytic hydrogenation activity of Pd and bimetallic Au–Pd nanoparticles supported on high-porosity carbon materials

The processes of palladium deposition on various high-porosity carbon matrices (Sibunit, CMK-3) have been studied. Mesostructured carbon material CMK-3 was synthesized using a silicate template of SBA-15 type. Pd nanoparticles were loaded onto carbon matrices by metalorganic chemical vapour deposition (MOCVD) method using palladium(II) acetylacetonate precursor. Bimetal Au–Pd systems were synthesized by autoclave reduction of gold(III) chloride complexes on Pd-containing carbon matrices. Structure of the obtained composite particles was studied by electron microscopy and X-ray diffraction. The average diameter of Pd particles on Sibunit is about 10, and 5–6 nm on CMK-3. The catalytic activity of the synthesized materials was studied in the reaction of furfural diethyl acetal (FDEA) hydrogenation, using gas–liquid chromatographic analysis. There is significant difference in catalytic activity of MOCVD-Pd/C compared to conventional impregnated Pd/C systems: the hydrogenation rate is 3–6 times higher with MOCVD-derived catalysts. Introducing Au into a MOCVD-Pd/C catalyst increases the hydrogenation rate threefold. Considerable difference in the composition of hydrogenation products was observed between these differently prepared catalysts.

Structured microreactor with gold and palladium on titania: Active, regenerable and durable catalyst coatings for the gas-phase partial oxidation of 1-butanol

Structured microreactors coated with catalytically active porous layers have emerged as a promising replacement for conventional reactors because they are inherently safe to operate in nearly isothermal conditions within the kinetic regime. Bio-based 1-butanol is commonly produced by acetone-butanol-ethanol (ABE) fermentation and is considered an important platform chemical that will benefit in the share of value-added chemicals through the development of new catalytic processes. In this study, monometallic gold (Au) and palladium (Pd), as well as bimetallic Au-Pd nanoparticles, supported on titania (TiO2) were prepared by a sol-immobilization method, characterized, coated on structured microreactor plates and tested for their catalytic activity in the gas-phase partial oxidation of 1-butanol to n-butyraldehyde. A customized structured catalyst testing microreactor was used. The average noble metal particle size for the catalyst coatings was determined to be approximately 3.6 nm for Au and Au-Pd catalysts, and the noble metal nanoparticles were evenly distributed. The catalyst coating was 17 ± 7 μm in thickness. The studied coated catalysts (TiO2, Au/TiO2, Pd/TiO2, and Au-Pd/TiO2) were all active for the partial oxidation of 1-butanol. The Au/TiO2 (0.6 wt%) catalyst showed the highest yield (20%) of n-butyraldehyde at 300 °C. The introduction of Pd onto Au/TiO2 or TiO2 shifted the product distribution at 250 °C towards retro-hydroformylation and oxidation products (propene, carbon monoxide and carbon dioxide). All of the coated catalysts that were tested were mechanically stable. The nano Au/TiO2 could be regenerated in situ and showed reproducible activities and yields in over 50 test runs. Structured microreactors coated with gold nanoparticles supported on titania show promise as a reusable and mechanically stable device for the process development of n-butyraldehyde production in ABE fermentation plants.

Aerobic oxidation of 5-hydroxymethylfurfural to 2,5-difurancarboxylic acid over Pd-Au nanoparticles supported on Mg-Al hydrotalcite

A series of reconstructed hydrotalcite supported monometallic Au or Pd and bimetallic Pd-Au nanoparticles with various Pd/Au ratios were synthesized. The physicochemical properties of these catalysts were charaterized by X-ray diffraction (XRD), X-ray photoelectronic spectroscopy (XPS), Transimission electron microscopy, N2 adsorption, etc. The catalysts were used for the aerobic oxidaiton of 5-hydroxymethylfurfural(HMF) into 2,5-furandicarboxylic acid (FDCA) in an alkaline aqueous solution. The monometallic Pd or Au catalyst could not oxidize the intermediate product-5-hydroxymethyl-2-furanic acid (HMFCA), while bimetallic Pd-Au catalysts exhibited good performances for HMFCA oxidation. A high yield of FDCA up to 90% was achieved over the Pd-Au/HT catalyst with the Au/Pd ratio of 4 at 60 °C for 6 h. The enhanced oxidation activity of HMF for the bimetallic catalysts is attributed to the syneretic effect between Au and Pd nanoparticles and the formation of smaller particle size that facilicates the oxidation of HMF to FDCA. The Pd-Au/HT(1 :4) catalyst also exhibited a good stabiblity without significant loss in FDCA yield after five succesive cycles.

DNA-Encoded Morphological Evolution of Bimetallic Pd@Au Core-shell Nanoparticles from a High-indexed Core.

DNA-mediated synthesis of nanoparticles with different morphologies has proven to be a powerful method to synthesize and access many exclusive shapes and surface properties. While previous studies employ seeds that contain relatively low-energy facets, such as a simple cubic palladium seed in the synthesis of Pd-Au bimetallic nanoparticles, few studies have investigated whether DNA molecules can still exert their influence when the synthesis uses a seed that contains high-energy facets. Seeds that are enclosed by such high-energy facets or sites are known to act as easy nucleation sites in nanoparticles growth and could potentially suppress the effect of DNA. To answer this question, we herein report DNA-encoded control of morphological evolution of bimetallic Pd@Au core-shell nanoparticles from a concave palladium nanocube seed that contains high indexed facets. Based on detailed spectroscopic and SEM studies of time-dependent growth of the bimetallic nanoparticles, we found that each of 10-mer DNA molecules (T10, G10, C10 and A10) has a unique way of interacting with both the seed's surface and the precursor. Among them, the most important factor is the binding affinity of the nucleobase to the Pd surface, with the A10 possessing the highest binding affinity and thus capable of stabilizing the seed's high energy surfaces. Furthermore, for bases with lower binding affinity (T10, G10 and C10) than A10, the growth is completely dictated by the seed's surface energy initially, but the later growth can still be influenced by the different DNA sequences, resulting in four unique morphologically different Pd@Au bimetallic nanoparticles. The effect of these DNA molecules with medium binding affinity can only be observed when there is more deposition of Au. Based on the above results, a scheme for the DNA controlled growth is proposed. Together these results have provided insights into factors governing DNA-mediated growth of core-shell structures using seeds with high-energy sites, and the insights can readily be applied to other bimetallic systems that adopt seed-mediated synthesis.

Porous Nanocrystalline Silicon Supported Bimetallic Pd-Au Catalysts: Preparation, Characterization, and Direct Hydrogen Peroxide Synthesis.

Bimetallic Pd-Au catalysts were prepared on the porous nanocrystalline silicon (PSi) for the first time. The catalysts were tested in the reaction of direct hydrogen peroxide synthesis and characterized by standard structural and chemical techniques. It was shown that the Pd-Au/PSi catalyst prepared from conventional H2[PdCl4] and H[AuCl4] precursors contains monometallic Pd and a range of different Pd-Au alloy nanoparticles over the oxidized PSi surface. The PdAu2/PSi catalyst prepared from the [Pd(NH3)4][AuCl4]2 double complex salt (DCS) single-source precursor predominantly contains bimetallic Pd-Au alloy nanoparticles. For both catalysts the surface of bimetallic nanoparticles is Pd-enriched and contains palladium in Pd0 and Pd2+ states. Among the catalysts studied, the PdAu2/PSi catalyst was the most active and selective in the direct H2O2 synthesis with H2O2 productivity of 0.5 at selectivity of 50% and H2O2 concentration of 0.023 M in 0.03 M H2SO4-methanol solution after 5 h on stream at −10°C and atmospheric pressure. This performance is due to high activity in the H2O2 synthesis reaction and low activities in the undesirable H2O2 decomposition and hydrogenation reactions. Good performance of the PdAu2/PSi catalyst was associated with the major part of Pd in the catalyst being in the form of the bimetallic Pd-Au nanoparticles. Porous silicon was concluded to be a promising catalytic support for direct hydrogen peroxide synthesis due to its inertness with respect to undesirable side reactions, high thermal stability, and conductivity, possibility of safe operation at high temperatures and pressures and a well-established manufacturing process.

Direct growth of ultrasmall bimetallic AuPd nanoparticles supported on nitrided carbon towards ethanol electrooxidation

Bimetallic nanoparticles (NPs) show interesting synergy to enhance the activity and durability in electrocatalytic alcohol oxidation compared to single-component metal NPs. The synthesis of bimetallic NPs often carried out in solution brings challenges in separating, loading and dispersing these NPs on conductive carbon supports. We herein report the direct growth of well-defined AuPd bimetallic NPs in the size range of 2–5 nm on nitrided carbon support. Our method is based on a seed-mediated growth method using Au seeds (1.8 ± 0.3 nm) supported on nitrided carbon. We show that the sizes and surface compositions of bimetallic NPs are precisely controllable. The resultant core-shell AuPd bimetallic NPs are thermally stable and they can be converted to alloyed AuPd NPs when subjected to thermal activation at 250 °C for 1 h. The chemical compositions of the AuPd alloyed NPs have been investigated by combining electron microscopy dispersive X-ray analysis, X-ray photoelectron spectroscopy and surface oxygen desorption using electrochemical reduction of catalysts. The catalytic activity, stability, poisoning tolerance and charge transfer resistance of AuPd alloyed NPs for the ethanol electrooxidation are largely enhanced compared to single-component NPs. Au0.45Pd0.55-5 nm exhibited the superior specific activity of 1.11 mA/cm2 and mass activity of >0.4 A/mgmetal toward ethanol oxidation, approximately 5 times more active than commercial Pd/C. We expect that this synthetic method will be of interest to prepare metallic electrocatalysts having defined nanostructures and compositions directly on conductive carbon for applications in fuel cells and batteries.

TiO2 Supported gold–palladium catalyst for effective syngas production from methane partial oxidation

The CO and H2 (syngas) production from methane partial oxidation (MPO) using TiO2 supported Au-Pd bimetallic catalysts are discussed. The supported Au, Pd and Au-Pd bimetallic nanoparticles were prepared by an incipient wetness impregnation or co-impregnation method and were characterized. The supported Au-Pd catalyst was selective for reforming and was more active compared to bare TiO2, TiO2 supported Au only, or Pd only catalysts. The catalyst properties before and after MPO reaction were investigated, including the stability of the TiO2 support, and the stability of Au and Pd nanoparticles. The supported Au-Pd catalyst has the highest TON (TONH2 = 23 at 650 °C), compared to supported Au catalyst (TONH2 < 1) and supported Pd catalyst (TONH2 < 1). Based on the analysis of outlet gases from the MPO reaction in a flow reactor, synergetic effects between Au and Pd, where Pd activates CH bonds while gold modulates the behavior of oxygen at the catalyst surface, are shown to contribute to MPO. Additionally, the Au-Pd/TiO2 material shows long-term activity (>12 h) for the MPO reaction at 600 °C.

Bimetallic Au-Pd nanoparticles on 2D supported graphitic carbon nitride and reduced graphene oxide sheets: A comparative photocatalytic degradation study of organic pollutants in water

Novel and sustainable bimetallic nanoparticles of Au-Pd on 2D graphitic carbon nitride (g-C3N4) and reduced graphene oxide (rGO) sheets was designed adopting an eco-friendly chemical route to obtain Au-Pd/g-C3N4 and Au-Pd/rGO, respectively. Elimination of hazardous pollutants, particularly phenol from water is urgent for environment remediation due to its significant carcinogenicity. Considering this aspect, the Au-Pd/g-C3N4 and Au-Pd/rGO nanocomposites are used as photocatalyst towards degradation of toxic phenol, 2-chlorophenol (2-CP) and 2-nitrophenol (2-NP) under natural sunlight and UV light irradiation. Au-Pd/g-C3N4 nanocomposite exhibited higher activity then Au/g-C3N4, Pd/g-C3N4 and Au-Pd/rGO nanocomposites with more than 95% degradation in 180 min under sunlight. The obtained degradation efficiency of our materials is better than many other reported photocatalysts. Incorporation of nitrogen atoms in the carbon skeleton of g-C3N4 provides much better properties to Au-Pd/g-C3N4 nanocomposite than carbon based Au-Pd/rGO leading to its higher degradation efficiency. Due to the presence of these nitrogen atoms and some defects, g-C3N4 possesses appealing electrical, chemical and functional properties. Photoluminescence results further revealed the efficient charge separation and delayed recombination of photo-induced electron-hole pairs in the Au-Pd/g-C3N4 nanocomposite. Generation of reactive oxygen species during photocatalysis is well explained through photoluminescence study and the sustainability of these photocatalyst was ascertained through reusability study up to eight and five consecutive cycles for Au-Pd/g-C3N4 and Au-Pd/rGO nanocomposites, respectively without substantial loss in its activity. Characterization of the photocatalysts after reaction signified the stability of the nanocomposites and added advantage to our developed photocatalytic system.

Tuning Pd–Au Bimetallic Catalysts for Heterogeneous Parahydrogen-Induced Polarization

The heterogeneous hydrogenation of propene over supported Pd–Au bimetallic nanoparticles was investigated using NMR and the parahydrogen-induced polarization (PHIP) technique. The composition and structure of Pd–Au/TiO2 catalysts were correlated to both catalytic activity and pairwise hydrogen addition. Sol-immobilization, impregnation, and deposition–precipitation methods were used for preparation of the Pd–Au bimetallic catalysts. A strong signal enhancement was observed on the bimetallic catalyst prepared through the sol-immobilization method, up to 24-fold higher than that with the other two methods. The polyvinyl alcohol (PVA) stabilizer bound to the metal surface was responsible for the enhanced PHIP effect. The removal of the PVA ligands by water washing and calcination treatments shows a significant effect on the hydrogen pairwise addition. Increasing the Au content in the bimetallic alloy led to a promotion of the pairwise selectivity due to the ensemble effect. The pairwise selectivity could be tuned by the morphologies of Pd–Au structures; the Au-shell/Pd-core morphology produced a higher pairwise selectivity than that of the Pd-shell/Au-core structure, while the random PdAu alloy showed the best PHIP effect.

Photocatalytic Ullmann coupling of aryl halides by a novel blended catalyst consisting of a TiO2 photocatalyst and an Al2O3 supported Pd–Au bimetallic catalyst

Synergy of TiO2 photocatalyst and Pd–Au bimetallic nanoparticles is essential for the efficient photocatalytic Ullmann coupling of aryl halides.

One-Step Synthesis of AuPdNPs/ERGO Nanocomposite for Enhanced Electrochemical Sensing of Cr(VI) in Water

One-step electrochemical approach for synthesis of AuPdNPs/ERGO nanocomposite has been developed for Cr(VI) sensing in water. The bimetallic AuPd nanoparticles and electrochemical reduced graphene oxide (ERGO) composite (AuPdNPs/ERGO) were reduced from H2PdCl4, HAuCl4 and GO mixed solution and deposited onto glass carbon electrode (GCE) through cyclic voltammetry, simultaneously. The bimetallic AuPdNPs were homogeneously modified on graphene nanosheets and characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM) and energy-dispersive X-ray spectroscopy (EDX) technique. Based on the voltammetric results, the bimetallic AuPdNPs/ERGO/GCE had higher catalytic activity for Cr(VI) determination, compared with AuNPs/GCE, PdNPs/GCE and ERGO/GCE obtained by the same method. The fabricated AuPdNPs/ERGO/GCE shows good relationship in two concentration ranges from 0.05 μM to 5 μM and 5 μM to 1000 μM, with a detection of 0.013 μM (at S/N = 3). In addition, the proposed modified electrode presents high selectivity, sensitivity and stability for Cr(VI) detection and a high recovery of more than 95% was obtained towards real water application, which makes it favorable for the further practical field monitoring.

Au-Pd bimetallic nanoparticles supported on a high nitrogen-rich ordered mesoporous carbon as an efficient catalyst for room temperature Ullmann coupling of aryl chlorides in aqueous media.

An ionic liquid derived highly nitrogen-rich mesoporous carbon supported Au-Pd alloy was found to be an efficient and recyclable catalyst for the Ullmann coupling reaction of various aryl chlorides at room temperature in aqueous media.

Compositional effect of two-dimensional monodisperse AuPd bimetallic nanoparticle arrays fabricated by block copolymer nanopatterning on catalytic activity of CO oxidation.

We present a straightforward approach for fabricating AuPd nanocatalysts based on self-assembled block copolymer nanopatterning. CO oxidation was carried out on AuPd alloy nanoparticles and the activity increased with increasing Pd content; this synergistic activity can be precisely tuned by varying the chemical composition. Theoretical calculations suggest that Pd clusters are required to bind and dissociate O2 for oxidation of coadsorbed CO molecules. Our results suggest that the geometric configuration of the Pd atoms on the surface are a key factor in the catalytic activity.

General Synthetic Route toward Highly Dispersed Ultrafine Pd-Au Alloy Nanoparticles Enabled by Imidazolium-Based Organic Polymers.

Bimetallic Pd-Au nanoparticles (NPs) usually show superior catalytic performances over their single-component counterparts, the general and facile synthesis of subnanometer-scaled Pd-Au NPs still remains a great challenge, especially for electronegative ultrafine bimetallic NPs. Here, we develop an anion-exchange strategy for the synthesis of ultrafine Pd-Au alloy NPs. Simple treatment of main-chain imidazolium-based organic polymer (IOP) with HAuCl4 and Na2PdCl4, followed by reduction with NaBH4 generated Pd-Au alloy NPs (Pd-Au/IOP). These NPs possess an unprecedented tiny size of 1.50 ± 0.20 nm and are uniformly dispersed over IOP. The electronic structure of the surface Pd and Au atoms is optimized via electron exchange during alloying, a net charge flowing resulting from counteranions is injected into Au and Pd to form a strong ensemble effect, which is responsible for a remarkably higher catalytic activity of Pd-Au/IOP in the hydrolytic dehydrogenation of ammonia borane than those of monometallic counterparts.

Fingerprint Feature of Atomic Intermixing in Supported AuPd Nanocatalysts Probed by X-ray Absorption Fine Structure

We report on a systematic study of AuPd bimetallic nanoparticles (NPs) prepared from two-step sputtering deposition in the suspension of graphene and ionic liquid using X-ray absorption fine structure (XAFS) spectroscopy. As-synthesized AuPd bimetallic catalysts possess well-enhanced activity and stability compared with monometallic (Au-only or Pd-only) catalysts, suggesting the synergistic effect upon alloying. A structural model with the introduction of Pd to Au cluster is provided to study the formation of bimetallic NPs and to offer detailed insights into the local structure information (interaction between Au and Pd). A novel and significant fingerprint is proposed to depict the intermixing structure of AuPd bimetallic NPs. The present XAFS study reveals a fingerprint feature in k-space, which can be an evaluation of the extent of the Au–Pd intermixing on the atomic scale, corresponding to the catalytic activity of bimetallic nanoparticles. The systematic XAFS-based methodology, demonstrated here on ...

On the development of kinetic models for solvent-free benzyl alcohol oxidation over a gold-palladium catalyst

Bimetallic Au-Pd nanoparticles supported on TiO2 show excellent catalytic activity and selectivity to benzaldehyde in the solvent-free transformation of benzyl alcohol to benzaldehyde, where toluene is the main observed by-product, together with smaller amounts of benzoic acid, benzyl benzoate and dibenzyl ether. However, despite the industrial relevance of this reaction and importance of tuning the selectivity to the desired benzaldehyde, only a few attempts have been made in the literature on modeling the reaction kinetics for a quantitative description of this reaction system. A kinetic model for the oxidation of benzyl alcohol over Au-Pd is proposed in this paper. The model assumes that hydrogenolysis, disproportionation and dehydrogenation reactions may occur in parallel, and it has been found satisfactory after a model discrimination procedure was applied to a number of simplified candidate models developed from microkinetic studies. Despite its relative simplicity, the proposed model is capable of representing the reactant conversion and distribution of products observed in experiments carried out at different temperature, pressure and catalyst mass in a stirred batch reactor. Major findings include the quantitative evaluation of the impact of hydrogenolysis and disproportionation pathways on benzaldehyde production. At low temperature the disproportionation reaction is the dominant route to toluene formation, while hydrogenolysis dominates at high temperature.

Bimetallic Effect of Single Nanocatalysts Visualized by Super-Resolution Catalysis Imaging.

Compared with their monometallic counterparts, bimetallic nanoparticles often show enhanced catalytic activity associated with the bimetallic interface. Direct quantitation of catalytic activity at the bimetallic interface is important for understanding the enhancement mechanism, but challenging experimentally. Here using single-molecule super-resolution catalysis imaging in correlation with electron microscopy, we report the first quantitative visualization of enhanced bimetallic activity within single bimetallic nanoparticles. We focus on heteronuclear bimetallic PdAu nanoparticles that present a well-defined Pd–Au bimetallic interface in catalyzing a photodriven fluorogenic disproportionation reaction. Our approach also enables a direct comparison between the bimetallic and monometallic regions within the same nanoparticle. Theoretical calculations further provide insights into the electronic nature of N–O bond activation of the reactant (resazurin) adsorbed on bimetallic sites. Subparticle activity correlation between bimetallic enhancement and monometallic activity suggests that the favorable locations to construct bimetallic sites are those monometallic sites with higher activity, leading to a strategy for making effective bimetallic nanocatalysts. The results highlight the power of super-resolution catalysis imaging in gaining insights that could help improve nanocatalysts.

Variation of SMSI with the Au:Pd Ratio of Bimetallic Nanoparticles on TiO2(110)

Au/Pd nanoparticles are important in a number of catalytic processes. Here we investigate the formation of Au–Pd bimetallic nanoparticles on TiO2(110) and their susceptibility to encapsulation using scanning tunneling microscopy, as well as Auger spectroscopy and low energy electron diffraction. Sequentially depositing 5 MLE Pd and 1 MLE Au at 298 K followed by annealing to 573 K results in a bimetallic core and Pd shell, with TiOx encapsulation on annealing to ~ 800 K. Further deposition of Au on the pinwheel type TiOx layer results in a template-assisted nucleation of Au nanoclusters, while on the zigzag type TiOx layer no preferential adsorption site of Au was observed. Increasing the Au:Pd ratio to 3 MLE Pd and 2 MLE Au results in nanoparticles that are enriched in Au at their surface, which exhibit a strong resistance towards encapsulation. Hence the degree of encapsulation of the nanoparticles during sintering can be controlled by tuning the Au:Pd ratio.

Characterization Microstructural and Electrochemical of AgPd Alloy Bimetallic Nanoparticles

ABSTRACTBimetallic nanoparticles are of special interest for their potential applications to fuel cells, among the bimetallic systems, AuPd bimetallic nanoparticles have received great interest as they can be widely used as effective catalysts for various electrochemical reactions. Monodisperse AgPd alloy nanoparticles were synthesized by polyol method using silver nitrate and potassium tetrachloropalladate(II) in ethylene glycol as the reducing agent at 160 °C. Structural, compositional and electrochemical characterizations of synthesized bimetallic nanoparticles were investigated. High-angle annular dark field scanning/transmission electron microscopy (HAADF-STEM) images and parallel beam X-ray diffraction (XRD) of the bimetallic nanoparticles were obtained. XRD and the contrast of the HAADF-STEM images show that the bimetallic nanoparticles have an alloy structure. Cyclic voltammetry was carried out in order to confirm the electrochemical responses of the AgPd/C electrocatalysts for methanol oxidation. Thanks to the narrow size distribution of the AgPd alloy bimetallic nanoparticles (9.15 nm) the supported AgPd/C electrocatalysts have high catalytic activity toward methanol electro-oxidation.

Reduced graphene oxide-supported Pd@Au bimetallic nano electrocatalyst for enhanced oxygen reduction reaction in alkaline media

Rational design and synthesis of core-shell bimetallic nanoparticles with tailored structural and functional properties is highly sought to realize clean and energy-efficient fuel cell systems. Herein, PdAu bimetallic nanoparticles (NPs) with core-shell morphology (PdCore–AuShell) were fabricated on the surface of reduced graphene oxide (RGO) support by a facile two-step protocol. In the first step, PdCore–AgShell bimetallic NPs were synthesized on RGO support by reducing Pd2+and Ag+ ions with methyl ammonia borane (MeAB). Later, PdCore–AuShell bimetallic NPs were conveniently fabricated on RGO support via a galvanic replacement strategy involving sacrificial oxidation of metallic silver and reduction of gold ions. The resulting core/shell bimetallic NPs were characterized by X-ray diffraction (XRD), High-resolution transmission electron microscopy (HR-TEM), Energy dispersive X-ray spectroscopy (EDS), Fourier-Transform Infrared Spectroscopy (FT-IR) and cyclic voltrammetry (CV). The electrocatalytic performance of core/shell nanostructures for the room temperature oxygen reduction reaction (ORR) in alkaline media were systematically performed by CV. The electrode-area-normalized ORR activity of RGO-supported PdCore–AuShell NPs was higher than the corresponding commercially available carbon-supported Pt nanoparticles (Pt/C) at −0.8 V vs Ag/AgCl (satd. KCl) (6.24 vs 5.34 mA cm−2, respectively). Further, methanol-tolerant ORR activities of as-synthesized catalysts were also studied. The Au-on-Pd/RGO bimetallic NPs presented enhanced ORR activity both in presence and in the absence of methanol in comparison with a commercial Pt/C catalyst and as-synthesized Pd/RGO and Au/RGO catalysts. The enhanced catalytic activities of core/shell structures might be resulted owing to the optimized core/shell structure comprising of a small Pd core and a thin Au shell and synergistic effects offered by Pd and Au. The present synthesis protocol demonstrated for two-layer structure can be extended to multi-layered structures with desired functions and activities.