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The present investigation deals with the development, characterization and application of nanostructured Pd doped Ni electrodes (Pd@Ni), which uses the electrochemical properties of Pd in synergy with the magnetic properties of Ni for biosensors development. The Pd@Ni electrodes have been characterized by X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. It has been shown that palladium presented spherical assemblies ranging 150–200 nm medium diameter size that covers large areas of the electrode surface while metallic nickel, which confers magnetic properties, showed a uniform granular structure with sizes between 20 and 50 nm. Cyclic voltammetry and electrochemical impedance spectroscopy were performed to understand the electrochemical process at the Pd@Ni electrodes in neutral media. The Pd@Ni electrodes were applied for the electrochemical detection of H 2 O 2. Finally, Ni nanoparticles (NiNP) functionalized with the model enzyme glucose oxidase (GOx-NiNP) have been attached to the Pd@Ni electrode solely through magnetic interactions, and the obtained GOx-NiNP/Pd@Ni biosensor applied for glucose determination in aqueous solutions by fixed potential amperometry at −0.05 V (vs Ag/AgCl) with reduced interferences. Image 10197 • Palladium doped nickel electrodes and nickel nanoparticles. • Benefits from the catalytic effect of Pd and the magnetic properties of Ni. • Oxidase immobilization solely through magnetic interactions. • Palladium doped nickel electrodes for the detection of H 2 O 2. • Biosensor operates at low potential values avoiding interfering compounds. [ABSTRACT FROM AUTHOR]

3D-ordered porous nitrogen and sulfur co-doped carbon (NS/C) is synthesized from the functionalized fluidic acrylonitrile telomer (ANT) as C, N and S source. The dispersed PdCuW nanoparticles with an average size of 5.25 nm are supported on the walls of the NS/C by a glycol reduction method. Compared with 20%Pd black (Pd/C), NS/C and 20%Pd-NS/C, it is found that PdCuW-NS/C composite with 11.4 wt% Pd exhibits superior catalytic activity for oxygen reduction reaction (ORR) in alkaline solution. Moreover, PdCuW-NS/C possesses higher capacities, lower overpotentials and better cyclic stability as cathode materials for Li-O 2 batteries; the cyclic retention of more than 70 cycles are achieved at 300 mA g −1 with the restricted capacity at 500 mAh g −1 . [ABSTRACT FROM AUTHOR]

Manganese oxide (MnO x )-based hybrid electrode materials have been designed by electrochemical deposition on carbon cloth preliminary activated by palladium (Pd) nanoparticles. The synthesis conditions (current density, deposition time) were chosen in such a way as to achieve a stable structure of MnO x with a large surface area. The structural parameters and surface morphology of materials obtained are characterized by Scanning Electron and Transmission Electron Microscopy (SEM, TEM), Raman spectroscopy, X-ray Photoelectron Spectroscopy (XPS), etc. The electrochemical behavior was investigated by cyclic voltammetry, galvanostatic charge/discharge and impedance spectroscopy. The attained results indicate that MnO x deposits reviled birnessite-type structural feature. Apart from that, the morphology of MnO x transformed with increasing of current density from needlelike structure to loosely-packed thin sheets and then to closed-packed thicker sheets structures. Different morphology exhibits different specific surface area and electrochemical efficiency. Hence electrochemical analysis reviled the highest specific capacitance (186 F g −1 ) and cyclic stability for MnO x PdCC with obtained at current density of 1 mA cm −2 . It can be explained by the formation of a less dense structure of MnOx (loosely-packed thin sheets) with large specific surface area and thus better permeability for Na + and SO 4 −2 ions. As to the role of Pd, its nanoparticles deposited on CC can play a dual role, namely electron conducting passway between CC and MnO x and structure–guiding agent of manganese oxides nucleation and grows. [ABSTRACT FROM AUTHOR]

Monodispersed metal (Cu, Pd, Pt, Rh) nanoparticles have been anchored on reduced graphene oxide (rGO) by a facile electrochemical co-deposition method. Scanning electron microscopic images reveal the presence of homogeneously dispersed metal nanoparticles on the rGO nanosheets. The as-prepared nanocomposites demonstrate excellent electrocatalytic activity for electroreduction of NO 3 − and NO 2 − . The mechanisms associated with the best performed Rh-rGO were studied in detail by cyclic voltammetry, X-ray photoelectron spectroscopic (XPS) and Fourier transformed ac voltammetry. It is proposed that the electrocatalytic reduction of NO 3 − on Rh-rGO is catalyzed by an adsorbed H* (H + aq + e − → H*) species to form NO 2 − which is further catalyzed by H* to form a surface confined NO* intermediate. Rh-rGO displays high electrochemical stability for NO 3 − reduction over the pH range of 4–9, which could be a suitable candidate for applications in remediation of NO 3 − contamination. [ABSTRACT FROM AUTHOR]

The use of Ionic Liquids (ILs) to enhance the electrocatalytic activity of metal nanoparticles has garnered sustained research interest. However, current strategies involving ionic liquids do not exploit their use and advantages in chemical synthesis of metal nanoparticles. Herein, we demonstrate a straightforward method, which combines the advantages of ILs in nanoparticle synthesis with the potentials of ILs in electrocatalysis, for the synthesis of Pd nanoclusters for electrochemical oxidation of formaldehyde. This method relies on the use of 1-(2′-aminoethyl)-3-methyl-imidazolum tetrafluoroborate ionic liquid as stabilizers to directly generate Pd nanoclusters with average sizes of 1.8 ± 0.3 nm in a reaction medium consisting of water and methanol at room temperature. The electrochemical measurements prove that the ionic liquid-assisted Pd nanoclusters have mass-normalized activity approximately 7 times than that of commercial Pd/C catalysts for the oxidation of formaldehyde. [ABSTRACT FROM AUTHOR]

Palladium (Pd) is considered as a possible candidate as catalyst for proton exchange membrane fuel cells (PEMFCs) due to its high activity and affordable price compared to platinum (Pt). However, the stability of Pd is known to be limited, yet still not fully understood. In this work, Pd dissolution is studied in acidic media using an online inductively coupled plasma mass spectrometry (ICP-MS) in combination with an electrochemical scanning flow cell (SFC). Crucial parameters influencing dissolution like potential scan rate, upper potential limit (UPL) and electrolyte composition are studied on a bulk polycrystalline Pd (poly-Pd). Furthermore, a comparison with a supported high-surface area catalyst is carried out for its potential use in industrial applications. For this aim, a carbon supported Pd nanocatalyst (Pd/C) is synthesized and its performance is compared with that of bulk poly-Pd. Our results evidence that the transient dissolution is promoted by three main contributions (one anodic and two cathodic). At potentials below 1.5 V RHE the anodic dissolution is the dominating mechanism, whereas at higher potentials the cathodic mechanisms prevail. On the basis of the obtained results, a model is thereafter proposed to explain the transient Pd dissolution. [ABSTRACT FROM AUTHOR]

Defective Pd@Pd-Pt nanocubes (NCs) were successfully synthesized by a displacement deposition method. In this study, a Pt layer was predominantly deposited at the corners and edges of Pd NCs to form concave NC surfaces and a Pd-Pt shell with a Pd-only core. Additionally, rotating ring-disk electrode experiments were performed to determine the mass activities of these Pd@Pd-Pt NCs, which acted as oxygen reduction catalysts in a KOH solution. The concave Pd@Pd-Pt NCs (28.2 nm) exhibited a 1.7-fold higher activity than that of 7 nm Pt nanoparticles. After accelerated durability tests, the data indicated the prepared NCs retained nearly 80% of the initial activity for the oxygen reduction reaction. [ABSTRACT FROM AUTHOR]

Studies concentrated on the development of carbon supported Pd x Pt y /C electrocatalysts for the oxygen reduction reaction (ORR). The application of the reverse ‘water-in-oil’ microemulsion method allowed to obtain a number of electrocatalysts with metal nanoparticles of ca. 5–6 nm in size. Catalysts with the constant metal loading of 10 wt% and various Pd:Pt atomic ratios were investigated. The textural features of the PdPt/C catalysts (surface area, morphology) as well as the PdPt phase (metal particle size, bulk composition) were characterized by a number of techniques. A particular attention was paid to the characterization of the surface properties of the PdPt particles using cyclic voltammetry technique. For all Pt contents (5 to 70 at%) a segregation of metal components (Pt, Pd) occurred leading to the Pt enrichment in the top layers. The observed Pt enrichment manifested especially strongly for PdPt catalysts with bulk Pt content below 20 at%. The surface fraction of Pt as high as 0.8 to 0.9 was attained regardless of nominal Pt content, starting from 30 at%. Among the catalysts, those with Pt content of 50 and 70 at% exhibited the highest activity towards ORR in terms of positively shifted half-wave potential, even surpassing that of Pt/C. Moreover, the obtained specific activity and turnover frequency values also suggested similar activities of catalysts with Pt content of 50 and 70 at%. A negligible formation of hydrogen peroxide on these two catalysts, indicated almost exclusively a desired four-electron process leading to water formation. The observed effect of Pt content on ORR activity is discussed in terms of surface properties of the PdPt nanoparticles. [ABSTRACT FROM AUTHOR]

The present work investigates the electrocatalytic properties of the palladium nanoparticles based polymer nanocomposite towards sensing of Melatonin (MEL). The modification protocol involved a single step fabrication and was achieved using cyclic voltammetry. The sensing surface was characterized using voltammetry, FE-SEM, EDX and EIS. Quantitative estimation of MEL has also been carried out using square wave voltammetry in the linear concentration range of 5–100 μM and sensitivity and limit of detection of 0.1235 μA/μM and 0.09 μM respectively have been achieved. The surface modified sensor exhibited almost 3 fold improvement in the sensing properties in comparison to the unmodified surface. The proposed method was also successfully extended for the determination of MEL in commercially available pharmaceutical formulations and human urine samples. [ABSTRACT FROM AUTHOR]

Design of appropriate supporting materials is an alternative route to yield efficient Pt-free catalysts for ethanol oxidation reaction, which in practice may determine the conversion efficiency of direct alkaline ethanol fuel cells. In this work, graphene nanoribbons (GNRs) coated with MnO 2 are used as a unique supporting material for loading and dispersing Pd nanoparticles. XRD, TEM and XPS are applied to characterize the structure of as-synthesized Pd/MnO 2 /GNRs nanocomposite catalyst, revealing a good dispersion as well as a modification of electronic property of Pd nanoparticles. Electrochemical measurements demonstrate that the as-synthesized nanocomposite displays largely enhanced electrocatalytic activity and durability toward ethanol oxidation in alkaline media as compared to the other tested Pd-based catalysts with various supports. [ABSTRACT FROM AUTHOR]

Palladium nanoparticle–graphene nanosheet composite (PdNP–GN) is demonstrated as an efficient electrode material in energy storage applications in supercapacitors. Palladium nanoparticle (PdNP) decorated graphene nanosheet (GN) composite was synthesized via a chemical approach in a single step by the simultaneous reduction of graphene oxide (GO) and palladium chloride from the aqueous phase using ascorbic acid as reducing agent. The materials were characterized by scanning and high resolution transmission electron microscopy, Raman, X-ray diffraction and energy dispersive X-ray spectroscopy which demonstrate that the metal nanoparticles have been uniformly deposited on the surface of graphene nanosheets. The synthesized material has been analyzed by cyclic voltammetry, electrochemical impedance spectrometry and chronopotentiometry using 1 M KCl as the supporting electrolyte for its application in electrochemical double layer supercapacitors. PdNPs-GN composite showed improved electron transfer kinetics and superior capacitive performance with large specific capacitance of 637 F g −1 , excellent cyclic performance and maximum energy and power densities of 56 Wh kg −1 and 1166 W kg −1 , respectively at a current density of 1.25 A g −1 . This highlights the importance of the synergetic effects of electrochemically efficient Pd nanoparticles and graphene for energy storage applications in supercapacitors. [ABSTRACT FROM AUTHOR]

Despite the synergistic features arising from three-dimensional (3D) interconnected porous networks and constitutive reduced grpahene oxide (rGO) sheets, the one-pot synthesis and self-assembly of metal nanoparticles (NPs) deposited on the 3D rGO aerogels (GAs) is still challenging. Herein, we demonstrate the in-situ synthesis and direct deposition of 3D macroporous GA/palladium (Pd) NP hybrids for electrocatalytic applications. The discrete Pd NPs with a narrow size distribution of 8 to 10 nm are uniformly distributed onto the pore surface of GAs, while 3D macroporosity being constructed via a one-pot, hydrothermal process. The morphology, chemical composition and structure, and textural property of the 3D GA/Pd NP hybrids are comprehensively characterized. As a consequence of the coupling effect of the hierarchical porosity and the discrete Pd NPs, the 3D GA/Pd NP hybrids exhibit the greater electrocatalytic activity compared to those of 3D GAs and 2D rGO/Pd NP hybrids. [ABSTRACT FROM AUTHOR]

Palladium nanoparticles with controlled distributions of sizes and shapes were synthesized and characterized by TEM, HRTEM and voltammetric methods. The surfaces of these nanoparticles were modified by spontaneous adsorption of bismuth. The activity and selectivity towards glycerol electrooxidation reaction were determined by coupling cyclic volatmmetry with in situ infrared spectroscopy. Higher activity were observed on pure Pd nanoparticles presenting extended (100) and/or (111) surface domains (nanocubes and nanooctahedrons, respectively), with Pd nanocubes being the most active. The modification of the surface by spontaneous adsorption of bismuth not only greatly improves the activity of Pd nanocubes but also affects the reaction pathway of glycerol electrooxidation. The study allows a better understanding of the material structure/electrocatalytic behavior relationship, which is essential on a fundamental point of view for the determination of reaction mechanisms and on a practical point of view for the rational design of catalysts active and selective towards oxidation of polyols from biomass. [ABSTRACT FROM AUTHOR]

Modified carbon is fabricated by applying phenanthroline as nitrogen source and used as support (PMC) to immobilize Pd nanoparticles. Because the nitrogen-doping not only changes physicochemical and electronic properties of carbon but also serves as basic or coordination sites to stabilize and produce additional electronic activation for Pd, the Pd/PMC exhibits excellent electrochemcial performance for ethylene glycol oxidation. Compared to conventional Pd/C catalyst, the Pd/PMC catalyst has a larger electrochemically active surface area, 50 mV more negative onset potential, 1.77 times oxidation current and superior stability. [ABSTRACT FROM AUTHOR]

Carbon-doped TiO 2 nanocoating (TiO 2 -C) on carbon black (CB) was prepared and employed as the support of Pd catalyst for ethanol oxidation reaction (EOR) in alkaline media. The obtained catalyst was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and electrochemical measurements. TEM characterization shows that TiO 2 nanocoating is formed uniformly on CB and still preserves its structure with no apparent sintering after carbon doping, and Pd particles are well dispersed on the conductive TiO 2 -C support. XRD characterization shows that TiO 2 -C presents an anatase structure. XPS characterization shows that oxygen vacancy defects resulting from carbon doping present in TiO 2 -C. Cyclic voltammetry (CV) and chronoamperometry (CA) results demonstrate that the as-prepared Pd/TiO 2 -C catalyst exhibits much enhanced catalytic activity and stability for EOR in alkaline media than Pd/C catalyst. The enhanced activity presented by the Pd/TiO 2 -C catalyst may result from the strong interactions between TiO 2 and Pd, the facilitated oxidation removal of CH 3 CO ads intermediate, and the facilitated transportation of ethanol to Pd active sites. [ABSTRACT FROM AUTHOR]

A facile, rapid, and wet-chemical co-reduction method is developed for synthesis of platinum@palladium core-shell nanoparticles supported on reduced graphene oxide (denoted as Pt@Pd/RGO) with the assistance of caffeine, without any seed or template. Caffeine is used here as a structure-directing agent and a capping agent, which is critical to the formation of Pt@Pd core-shell nanoparticles. Furthermore, the as-synthesized Pt@Pd/RGO shows the enlarged electrochemically active surface area, remarkably enhanced catalytic activity, and improved stability for methanol oxidation reaction (MOR), compared to Pt/RGO, Pd/RGO, commercial Pt black and Pd black. [ABSTRACT FROM AUTHOR]

Highly ordered palladium nanoparticle modified TiO2 nanotube electrode (Pd/TiO2NT/Ti) was prepared by electrochemical anodization of a Ti sheet, followed by photocatalytic reduction process in palladium chloride solution. The prepared electrodes were characterized by SEM, EDX, and EIS techniques. The electrocatalytic oxidation of formaldehyde at the surface of Pd/TiO2NT/Ti was studied by cyclic voltammetry and chronoamperometry methods. Oxidation of formaldehyde was well evidenced by appearance of two well defined anodic peaks in the forward and backward scans during CV experiments. Effects of some parameters including formaldehyde concentration, scan rate, and upper potential limit on the electrooxidation performance of electrode were investigated. In comparison with some of the previously reported electrodes, the Pd/Ti/TiO2NTs anode exhibited superior performance for electrooxidation of formaldehyde with a very low overpotential and high current density. This electrode showed a good stability during experiments and after storage for a long time in dry condition. [ABSTRACT FROM AUTHOR]

Hybrids of graphene nanosheets (GNSs) with Pd and MMn2O4 (M=Mn & Co) have been prepared and investigated as electrocatalysts for the methanol oxidation (MOR) and oxygen reduction (ORR) reactions in 1M KOH at 25°C. Results show that incorporation of Mn3O4 (or CoMn2O4) into 40wt%Pd/GNS increases the electrocatalytic activity toward both the reactions (MOR and ORR) greatly; the observed enhancement in the activity being much higher with CoMn2O4 addition. It is observed that at an anodic potential, E=0.610V vs RHE, 8wt% CoMn2O4 addition improves the methanol oxidation current density of 40wt%Pd/GNS by more than 3 times. Similarly, at E=0.90V vs RHE, 5wt% CoMn2O4 addition improves the ORR activity of 40wt%Pd/GNS nearly two times. The stability of the active hybrid electrode is also found to be outstanding under both MOR and ORR conditions. Similar stabilities have not been found with other fuel cell catalysts. In a chronoamperometry experiment at E=0.626V vs RHE, the methanol oxidation current observed on Pd-8%CoMn2O4/GNS at 2min decreased by only ~5% at 120min. [ABSTRACT FROM AUTHOR]

Highlights: [•] Pd nanoparticles immobilized organic-inorganic hybrid nano-composite is synthesized. [•] It efficiently electrocatalyse hydrazine (HZ) oxidation at low overpotential. [•] Amperometric sensor for HZ determination is constructed with high sensitivity. [•] The sensor shows selective and stable response for HZ with minimum interferences. [ABSTRACT FROM AUTHOR]

Abstract: The PANI/Pd0 nanocomposite films with Pd nanoparticles embedded in the polyaniline (PANI), were successfully fabricated through the simple layer-by-layer (LBL) adsorption of PANI and PdCl6 2−, followed by the in situ electrochemical reduction of the incorporated PdCl6 2− in the multilayer film. The as-prepared composite films were characterized by X-ray photoelectron spectroscopy, UV–vis spectroscopy, Fourier-transform infrared, atomic force microscope and transmission electron microscopy. The size of Pd nanoparticles in the composite film could be fine-tuned in the range of about 2–22nm by varying the concentration of PdCl6 2−. PANI in the nano-structured PANI/Pd0 composite films still shows the good redox activity in neutral pH solution. The as-obtained PANI/Pd0 nanocomposite film presents an excellent electrocatalytic activity to hydrazine oxidation. And the catalytic performance is not only dependent on film thickness, but also Pd0 size. On the 5-bilayer PANI/Pd0 film with Pd0 particles 2nm in size, two calibration curves were found in the concentration ranges of 3.0×10−7–3.5×10−4 M and 5.0×10−4–1.2×10−2 M. And the minimal detectable concentration was down to 5.0×10−8 M on the electrode with 13 bilayers buildup. The substrate can be used repeatedly for consecutive detection of hydrazine with good stability. [Copyright &y& Elsevier]

Abstract: Palladium nanoparticles (PdNPs) modified indium tin oxide (ITO) electrode was fabricated via electrospinning followed by calcination. The results of scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) indicated the PdNPs were immobilized on the ITO electrode surface successfully. The electrochemical behavior of the modified electrodes could be adjusted easily by changing the collected time of electrospinning. The prepared electrodes exhibited high sensitivity, good reproducibility and stability toward NO2 −. The current responses were linear with NO2 − concentrations in a wide range with low detection limit. The proposed method can be successfully applied to the determination of NO2 − in real water samples. [Copyright &y& Elsevier]

Glucose biofuel cells are one of the promising power supplies with a competent long-term stability and power density. In this respect, catalysts of palladium (Pd) and platinum (Pt) metal nanoparticles film coated electrode were fabricated for biofuel cell. The Pt and Pd particles were electrochemically deposited onto glassy carbon (GC) electrode modified with poly(1,8-diaminonaphthalene), (p-1,8-DAN), via single or layer-by-layer electrodeposition. In results, Pt/p-1,8-DAN/GC, Pd/p-1,8-DAN/GC, Pt-Pd/p-1,8-DAN/GC and Pd-Pt/p-1,8-DAN/GC shell-core catalysts were fabricated and characterized by several analytical techniques such as AFM, EDX,SEM, TEM, and XPS, in addition to electrochemical methods. Their catalytic electrooxidation behaviors of glucose were investigated in alkaline medium. The as-prepared nano-catalysts showed improved electrocatalytic performances and better stability for glucose oxidation reaction (GOR) due to the presence of metal nanoparticles. The Pd as core and Pt as shell in Pt-Pd/p-1,8-DAN/GC catalyst exhibited higher electrochemically accessible surface area (157.58 m2/g) and a favored electrooxidation efficiency. Moreover, the bimetallic Pt-Pd shell-core electrode showed higher resistance to poisoning (tolerance 1.24) and a decrease in the onset potential to -0.28 V. These multipurpose electro-catalysts are a potential candidate for developing a novel glucose biofuel cell. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Palladium nanochains with uniform dispersion supported transition metal core-shell nanoparticles (TM core-shell , TM core-shell = Ni@NiO, Co@CoO) modified reduced graphene oxide (rGO) are synthesized through a facile two-step method as the catalysts for methanol electro-oxidation. The transition metal nanoparticle consists of transition metal core and transition metal oxide shell layer with an average particle diameter of about 35 nm, which can play an important role in adjusting the electronic structure of Pd. It can be attributed to the different support-metal synergistic interaction (SMSI) between TM core-shell -rGO support and Pd metal. In addition, the Pd/Co@CoO-rGO catalyst exhibits the highest electrocatalytic activity for methanol electro-oxidation, with the mass activity of 1786 mA mg−1, which is 7.01 times and 1.49 times as high as those of the commercial Pd/C and the commercial Pt/C, respectively. Furthermore, the Pd/Co@CoO-rGO catalyst keeps the best stability than the commercial Pd/C, the commercial Pt/C, Pd/rGO and Pd/Ni@NiO-rGO catalysts during all the test time. TM core-shell -rGO support provide us a new strategy of structure engineering for highly efficient methanol oxidation. • A novel Pd/TM core-shell -rGO hybrid electrocatalyst is prepared by a facile two-step method. • The electro-catalytic activity of Pd/Co@CoO-rGO catalyst is 7.01 times as high as that of the commercial Pd/C. • The enhanced electro-catalytic activity could be attributed to the support-metal synergistic interaction. • The Pd/Co@CoO-rGO catalyst will be a very promising catalyst in the commercialization of the alkaline DMFCs in future. [ABSTRACT FROM AUTHOR]