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 Electrocatalysis   [SJR: 0.883]   [H-I: 10]   Follow         Hybrid journal (It can contain Open Access articles)    ISSN (Print) 1868-2529 - ISSN (Online) 1868-5994    Published by Springer-Verlag  [2302 journals]
• Using the Alkynyl-Substituted Rhenium(I) Complex
(4,4′-Bisphenyl-Ethynyl-2,2′-Bipyridyl)Re(CO) 3 Cl as Catalyst
for CO 2 Reduction—Synthesis, Characterization, and Application
• Abstract: Abstract The synthesis, structure, photophysics, and spectroscopic characterization of an organometallic rhenium multichromophore compound carrying a central 2,2′-bipyridyl acceptor moiety with additional phenylethynyl substituents conjugated at the 4,4′-positions of the acceptor ligands and its effect on the electron density of the central rhenium atom as metal center for CO2 reduction is reported. The results were compared to fac-(2,2′-bipyridyl)Re(CO)3Cl and fac-(5,5′-bisphenylethynyl-2,2′-bipyridyl)Re(CO)3Cl. Cyclovoltammetric studies and rotating disk electrochemistry were performed for electrochemical characterization. Ultraviolet and visible (UV-vis) absorption, Fourier transform infrared (FTIR), and luminescence measurements were carried out for a spectroscopic characterization and compared to theoretical calculations at the density functional theory (DFT) level. In addition, the rhenium complex fac-(4,4′-bisphenyl-ethynyl-2,2′-bipyridyl)-Re(CO)3Cl was used as a novel catalyst for the electrochemical reduction of CO2 in homogeneous solution. Results showed an 11-fold increase in the current density under CO2 saturation and a catalytic second-order rate constant for CO formation of about 560 M−1 s−1 on a Pt working electrode. For further characterization of the CO2 reduction capabilities, bulk controlled potential electrolysis experiments were performed using a CO2-saturated acetonitrile electrolyte solution. The headspace product gas analysis yields CO as main reduction product with faradaic efficiencies of about 12 % over 5-h electrolysis time. Graphical Abstract
PubDate: 2015-03-01

• On the Temperature Performance of Ethanol Oxidation Reaction at
• Abstract: Abstract The present paper reports on ethanol oxidation reaction (EOR) investigated at catalytically modified nickel foam material. The EOR was studied in 0.1 M NaOH supporting electrolyte on Pd-activated nickel foam catalyst material, obtained by a spontaneous deposition method. Catalytic modification of Ni foam resulted in a composite material having superior EOR kinetics, as elucidated through corresponding values of a.c. impedance-derived charge-transfer resistance parameter (including temperature-dependence of the EOR over the temperature range 20–60 °C). The presence of a catalytic additive was disclosed from SEM and XRD analyses.
PubDate: 2015-03-01

• Microscopic Insights into the Chlorine Evolution Reaction on RuO 2 (110):
a Mechanistic Ab Initio Atomistic Thermodynamics Study
• Abstract: Abstract The frequently discussed mechanisms for the chlorine evolution reaction (CER)—Volmer–Tafel, Volmer–Heyrovsky, and Krishtalik—are assessed for the case of RuO2 within a mechanistic ab initio thermodynamics approach, employing the concept of Gibbs energy loss. The CER over the fully O-covered RuO2(110) surface, the stable surface configuration under CER conditions, is shown to proceed via the Volmer–Heyrovsky mechanism, i.e., the adsorption and discharge of the chloride ion are followed by the direct recombination of this surface species with a chloride ion from the electrolyte solution. The weak adsorption of the chloride ion on the fully O-covered RuO2(110) surface constitutes the elementary reaction step with highest Gibbs energy loss which has its origin in a too strong ruthenium–oxygen bond. Therefore, the activity of the model catalyst RuO2(110) can be enhanced by weakening the surface metal–oxygen bond such as realized with a monolayer of PtO2 coated on RuO2(110). Graphical Abstract ᅟ
PubDate: 2015-03-01

• An Easy Method for Calculating Kinetic Parameters of Electrochemical
Mechanisms: Temkin’s Formalism
• PubDate: 2015-03-01

• Selectivity of Nanocrystalline IrO 2 -Based Catalysts in Parallel Chlorine
and Oxygen Evolution
• Abstract: Abstract Nanocrystalline electrocatalysts with chemical composition corresponding to Ir1 − x M x O2 (M = Co, Ni, and Zn, 0.05 ≤ x ≤ 0.2) were prepared by the hydrolysis of H2IrCl6·4H2O solutions combined with nitrates and acetates of Ni, Zn, and Co. X-ray diffraction (XRD) analysis indicates that the dopant Co, Ni, and Zn cations substitute the Ir atoms in the rutile lattice. The prepared materials contain small inclusions of iridium metal on the level comparable with the detection of the XRD technique. The local environment of Co and Zn in the doped IrO2 materials conforms to a rutile model with a homogeneous distribution of the doping elements in the rutile lattice. The incorporated Ni is distributed in the rutile lattice non-homogeneously and tends to form clusters within rutile structure. The incorporation of Ni and Co enhances the activity of the prepared electrocatalysts in oxygen evolution. The modification of the IrO2 via doping process alters also the material’s selectivity in the parallel oxygen and chlorine evolution. Incorporation of Co and Zn cations shifts the selectivity of the catalysts toward oxygen evolution in chloride-containing media; the Ni incorporation leads to an enhancement of the selectivity toward chlorine evolution. Chlorine evolution is apparently limited by the number of the active catalytic sites on the electrode surface.
PubDate: 2015-03-01

• In Situ Analysis of Scan Rate Effects on Pt Dissolution Under Potential
Cycling Using a Channel Flow Double Electrode
• Abstract: Abstract To investigate the effect of scan rate (ν), the instantaneous dissolution of Pt under potential cycling 0.5–200 mV/s was studied using a channel flow double electrode. In an anodic scan, ν affects the initiation and inhibition of Pt dissolution during oxide formation. Slow scans induce Pt dissolution earlier, but soon suppress it. The extent of dissolution, however, did not show significant changes like the oxide development does when changing the ν. In a cathodic scan, the electrochemical dissolution of Pt2+ during oxide reduction speeds up with ν. The trivial chemical dissolution of unstable PtO2 into Pt4+ also occurs and increases with increasing ν.
PubDate: 2015-03-01

• Electrodeposition of Pt Nanoparticles on New Porous Graphitic Carbon
Nanostructures Prepared from Biomass for Fuel Cell and Methanol Sensing
Applications
• Abstract: Abstract We investigate the performance of an iron-doped porous graphitic carbon nanostructure (GCN) prepared from biomass for application in fuel cells and electrochemical sensors. By using cyclic voltammetry (CV), we show that these GCNs have appropriate electrochemical properties and exhibit a significantly high catalytic activity toward oxygen reduction without Pt catalyst. The GCNs were also used as a substrate for electrodeposition of Pt nanoparticles (Pt-NPs) to study electro-oxidation and sensing of methanol. The composition of Pt-NPs and GCNs show high catalytic affinity toward electro-oxidation of methanol in an acidic medium. The modified electrode with Pt-NPs and GCNs also could act as an effective sensor for determination of methanol concentration in natural pH. This sensor enables determination of methanol with a wide linear range (0.05–21.73 mM), low detection limit (20 μM, at S/N of 3), high sensitivity (11.49 μA cm−2 mM−1), and long-term stability (over 40 days). The present sensor also has low working potential (0.17 V) making it less prone to an interference effect. The resulting electrodes were characterized by using scanning electron microscopy, energy dispersive X-ray spectroscopy, and CV.
PubDate: 2015-03-01

• Self-adsorption of an Ultrathin Bismuth Layer in the Size of Ions on an Au
Surface
PubDate: 2015-03-01

• The Effects of Cathode Parameters on the Performance of
Poly(2,5-Benzimidazole)-Based Polymer Electrolyte Membrane Fuel Cell
• Abstract: Abstract The effects of electrode parameters on membrane electrode assembly performance including Pt loading, hydrophobicity during heat treatment, catalyst layer thickness and the amount of polytetrafluoroethylene (PTFE) in the cathode are investigated. The fuel cell performance is maximized via catalyst utilization by optimizing the phosphoric acid content in the electrodes. Heat treatment of gas diffusion electrode results in an increase in hydrophobicity and a decrease in phosphoric acid content in the catalyst layer, which drastically affects the fuel cell performance. In our conditions, a maximum fuel cell performance of 270 mW cm−2 was achieved at 160 °C with air using 1 mg Pt cm−2 total catalyst loading (20 % PTFE). The fuel cell performance and the poisoning effect of carbon monoxide in poly(2,5-benzimidazole) (ABPBI)-membrane-based high-temperature membrane electrode assemblies were investigated with respect to carbon monoxide concentrations. Fuel cell performance of Pt alloys (Pt-Cu/C, Pt-Fe/C, Pt-Ni/C) is compared with that of Pt/C at temperatures between 140 and 180 °C. It was observed that Pt-Cu/C alloy catalysts exhibit higher performance with lower catalyst loadings (0.4 mg Pt cm−2) than Pt/C catalyst. The performance of alloy catalysts follows the order of Pt-Cu/C > Pt-Fe/C > Pt-Ni/C > Pt/C.
PubDate: 2015-03-01

• High-Throughput Screening for Acid-Stable Oxygen Evolution
Electrocatalysts in the (Mn–Co–Ta–Sb)O x Composition
Space
• Abstract: Abstract Solar generation of fuel is a promising future energy technology, and strong acidic conditions are highly desirable for integrated solar hydrogen generators. In particular, water splitting near pH 0 is attractive due to the availability of high theoretical efficiency, high performance hydrogen evolution catalysts, and robust ion exchange membranes. The lack of a stable, earth-abundant oxygen evolution catalyst inhibits deployment of this technology, and development of such a material is hampered by the strong anti-correlation between electrochemical stability and catalytic activity of non-precious metal oxides. High-throughput screening of mixed metal oxides offers a promising route to the identification of new stable catalysts and requires careful design of experiments to combine the concepts of rapid experimentation and long-term stability. By combining serial and parallel measurement techniques, we have created a high-throughput platform to assess the catalytic activity of material libraries in the as-prepared state and after 2 h of operation. By screening the entire (Mn–Co–Ta–Sb)O x composition space, we observe that the compositions with highest initial activity comprised cobalt and manganese oxides, but combinations with antimony and tantalum offer improved stability. By combining the desired properties of catalytic activity and stability, the optimal composition regions are readily identified, demonstrating the success and fidelity of this novel high-throughput screening platform.
PubDate: 2015-03-01

• Direct Electrochemistry of Glucose Oxidase on a Three-Dimensional Porous
Zirconium Phosphate–Carbon Aerogel Composite
• Abstract: Abstract Biocompatible materials with large specific surface areas can play a crucial role in direct electron transfer between redox proteins and an electrode surface. Here, we report zirconium phosphate–carbon aerogel (ZrP-CA) composites with a large specific surface area and uniform nanopore distributions as matrix for glucose oxidase immobilization. The immobilized glucose oxidase displays two stable, well-defined redox peaks with an electron transfer rate constant of 9.34 s−1 in nitrogen-saturated phosphate-buffered saline (PBS) solution (0.1 M, pH 7.0), at a scan rate of 100 mV s−1. The modified electrode was also used as a glucose biosensor, which was found to exhibit a linear calibration range of 0.12–2.0 mM, sensitivity of 5.56 μA mM−1 cm−2 at an applied potential of −0.5 V, and detection limit of 34 μM based on a signal-to-noise ratio of 3. After 80 scan cycles, the decreases in the peak current were less than 8 %, indicating good stability of the as-prepared ZrP-CA. The unique characteristics of the ZrP-CA nanocomposite make it a good matrix for protein immobilization and biosensor preparation.
PubDate: 2015-02-26

• The Influence of Protonation on the Electroreduction of Bi (III) Ions in
Chlorates (VII) Solutions of Different Water Activity
• Abstract: Abstract We examined the electroreduction of Bi (III) ions in chlorate (VII) solutions under varied protonation conditions of the depolariser using voltammetric and impedance methods. The results of the kinetic parameter correlation lead to the statement that the changes in the amount of chloric (VII) acid against the amount of its sodium salt in the supporting electrolytes of the low water activity have a significant influence on the rate of Bi (III) ion electroreduction. The increase of the concentration of chloric acid sodium salt, as well as the chloric (VII) acid alone within the particular concentration of the supporting electrolyte, inhibits the process of Bi (III) ion electroreduction. It should be associated with the reorganisation of the structure of the double layer connected with the slow dehydration inhibited by ClO 4 − ions. The standard rate constants k s values with the increase of the chlorate (VII) concentrations for all the solutions examined of chlorates (VII) confirms the catalytic influence of the decrease of water activity on the process of Bi (III) ion electroreduction. The multistage process is confirmed by the non-rectilinear 1nk f = f(E) dependences.
PubDate: 2015-02-24

• Combinatorial Synthesis of Gold-Based Thin Films for Improved
Electrocatalytic Conversion of CO 2 to CO
• Abstract: Abstract Carbon dioxide electroreduction (CO2ER) was studied on 35 gold-based thin film catalysts sputtered on glassy carbon disks. A sputter-down setup was used for the deposition of these thin films in a combinatorial manner. Zinc and silver were employed in combination with gold in order to obtain new catalysts. Linear sweep voltammetry was employed to obtain the selectivity profile of each catalyst. Among the 35 catalysts, three ternary combinations (Au14Ag34Zn52, Au32Ag51Zn17, and Au16Ag10Zn74) and one binary combination (Au80Zn20) were identified as being active catalysts, reducing the dissolved CO2 in favor of proton reduction. Two ternary catalysts (Au16Ag10Zn74 and Au32Ag51Zn17) exhibited higher selectivity and lower overpotential for CO2ER than the pure metals. The Au80Zn20 binary catalyst exhibited the longest potential range where the selectivity for CO2ER remains constant. A decrease of the gold loading between 18 and 88 % was obtained for these catalysts, suggesting that they are promising candidates for an industrial application of CO2ER. Electrochemical impedance spectroscopy proved that the mechanism of CO2ER, involving two successive one-electron transfers, is identical on pure metals and combined sputtered catalysts.
PubDate: 2015-02-22

• A DEMS Study of the Reduction of CO 2 , CO, and HCHO Pre-Adsorbed on Cu
Electrodes: Empirical Inferences on the CO 2 RR Mechanism
• PubDate: 2015-01-27

• Recent Advances in Heteroatom-Doped Metal-Free Electrocatalysts for Highly
Efficient Oxygen Reduction Reaction
• Abstract: Abstract Heteroatom-doped metal-free electrocatalysts for oxygen reduction reaction (ORR) represent one of the most prominent families of electrocatalysts for fuel cells. While nitrogen (N)-doped carbon electrocatalysts toward ORR have experienced great progress throughout the past decades and yielded promising material concepts, also other heteroatom-doped catalysts have gained the researchers’ tremendous interest recently. Boron (B)-doping on carbon has been extensively studied, and due to the contrary electronic properties between N and B, a synergetic effect between the codoped N and B on carbon has been found for ORR. The carbons doped with sulfur (S), phosphorus (P), silicon (Si), and halogen (fluorine (F), chlorine (Cl), bromine (Br), iodine (I)) have also been studied as metal-free electrocatalysts for ORR in both experimental and theoretical ways. It has been known that the difference in electronegativity and size between the heteroatoms (N, B, S, P, Si, Cl, Br, I) and carbon can polarize adjacent carbon atoms to facilitate the oxygen reduction process. Especially, our research group reported the first F-doped or N,F-codoped carbon black as highly efficient ORR electrocatalysts which possess one of the best price/performance ratio ever. In this feature article, we review the recent research progress in the development of heteroatom-doped carbon-based metal-free electrocatalysts for ORR. Graphical Abstract Heteroatom-doped metal-free electrocatalysts for oxygen reduction reaction represent one of the most prominent families of electrocatalysts that are used in fuel cells. In this feature article, we review the recent research progress in the development of heteroatom-doped carbon-based metal-free electrocatalysts for ORR.
PubDate: 2015-01-16

• CO 2 Electroreduction on Cu-Modified Platinum Single Crystal Electrodes in
Aprotic Media
• Abstract: Abstract Techniques of electrode modification by copper deposits are developed that allow obtaining compact bulk quasi-epitaxial deposits on basal Pt(hkl) single crystal faces. The issues of the deposit roughness and characterization are discussed. Problems of drying and transferring electrodes with copper deposits into other solutions are considered. The obtained deposits are used for CO2 electroreduction in propylene carbonate and acetonitrile solutions of 0.1 M TBAPF6, and the relationship between the electrode surface structure and its electrocatalytic activity in CO2 electroreduction is discussed. We also demonstrate that the restructuring of Cu deposits occurs upon CO2 electroreduction. Complementary reactivity studies are presented for bare Pt(hkl) and Cu(hkl) single crystal electrodes. Cu-modified Pt(hkl) electrodes display the highest activity as compared to bare Pt(hkl) and Cu(hkl). Particularly, the Cu/Pt(110) electrode shows the highest activity among the electrodes under study. Such high activity of Cu/Pt(hkl) electrodes can be explained not only by the increasing actual surface area but also by structural effects, namely by the presence of a large amount of specific defect sites (steps, kinks) on Cu crystallites.
PubDate: 2015-01-01

• Electrochemical Behaviour of PSS-Functionalized Silica Films Prepared by
Electroassisted Deposition of Sol–Gel Precursors
• Abstract: Abstract Porous, electrically insulating SiO2 layers containing polystyrene sulfonate (PSS) were deposited on glassy carbon electrodes by an electrochemically assisted deposition method. The obtained material was characterized by microscopic, spectroscopic and thermal techniques. Silica-PSS films modify the electrochemical response of the glassy carbon electrodes against selected redox probes. Positively charged species show reduced diffusivities across the SiO2-PSS pores, which resulted in a concentration ratio higher than 1 for these species. The opposite behaviour was found for negatively charged redox probes. These observations can be interpreted in terms of the different affinity of the GC/SiO2-PSS-modified electrode for the electroactive species, as a consequence of the negatively charged porous silica.
PubDate: 2015-01-01

• Oxygen Electroreduction on Electrodeposited PdAu Nanoalloys
• Abstract: Abstract The electrocatalytic activity of electrodeposited palladium–gold (PdAu) alloys towards the oxygen reduction reaction (ORR) was studied in 0.05 M H2SO4 and 0.1 M KOH solutions using the rotating disc electrode (RDE) method. The electrochemical deposition was carried out at a constant potential and the ratio of concentrations of the precursors in the deposition bath was varied. The surface morphology of the deposits was studied using scanning electron microscopy (SEM), and the average particle size for PdAu alloys was determined to be about 6 nm. The X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV) studies suggest that the resulting PdAu coatings are alloyed. The ORR activities of the electrodes were compared by calculating the specific activities on the basis of the real electroactive surface area of Pd. The specific activity did not depend on the composition of the alloy in sulphuric acid solution, but in alkaline medium it increased with decreasing Pd content.
PubDate: 2015-01-01

• Enhanced Electrooxidation of Ethanol Using Pd/C + TiO 2 Electrocatalysts
in Alkaline Media
• Abstract: Abstract This work describes the use of Pd nanoparticles synthetized by the borohydride process and supported on physical mixtures of C + TiO2 toward the ethanol electrooxidation reaction in alkaline media. In this study, the C/TiO2 ratios were studied by ranging the mass proportions of C/TiO2—100:0, 80:20, 60:40, 40:60, 20:80, and 0:100. X-ray diffraction patterns showed the presence of Pd face-centered cubic (fcc) structure, and carbon and TiO2 in rutile and anatase phases. Transmission electron micrographs showed metal nanoparticles with average particle size between 5.5 and 7.2 nm for all electrocatalysts. Cyclic voltammograms of Pd/C + TiO2 electrocatalysts showed a decrease of Pd surface area with the TiO2 increasing, while the linear sweep and chronoamperometric results showed the Pd/C + TiO2 (40:60) as the most promising electrocatalyst toward ethanol electrooxidation. The best results obtained with this catalyst were attributed to the presence of carbon and TiO2 in intermediate proportions since TiO2 supplies OH species and also changes the Pd d-band by a strong metal support interaction, increasing the alcohol oxidation without a significant decrease of conductivity and surface area.
PubDate: 2015-01-01

• Thermodynamics of the Under-Potential Deposition of Hydrogen on
Polycrystalline Platinum in Aqueous Trifluoromethanesulfonic Acid Solution

• Abstract: Abstract Understanding of the electrocatalytic behavior of the Pt/Nafion® ionomer interface is of great importance to fuel cell technology. Trifluoromethanesulfonic acid (CF3SO3H) is used as an electrolyte because it is the smallest fluorinated sulfonic acid and serves as a suitable molecular model mimicking the Nafion® ionomer. The under-potential deposition of H (UPD H) on polycrystalline Pt electrode in CF3SO3H is investigated using cyclic voltammetry in the 278–333 K temperature (T) range. The general electrochemical adsorption isotherm is used to determine the Gibbs energy (−13 ≤ Δ ec − ads G°(HUPD) ≤ −27 kJ mol−1), entropy (−59 ≤ Δ ec − ads S°(HUPD) ≤ +20 J mol−1 K−1), and enthalpy (−8 ≤ Δ ec − ads H°(HUPD) ≤ −43 kJ mol−1) of electro-adsorption, and the Pt–HUPD surface bond energy (+225 ≤  $${E}_{\mathrm{Pt}-{\mathrm{H}}_{\mathrm{UPD}}}$$  ≤ +261 kJ mol−1). The lateral interactions between the HUPD adatoms are repulsive; the energy of lateral interactions is T-dependent (ω(HUPD) = a − b T) and is in the +14 ≤ ω(HUPD) ≤ +22 kJ mol−1 range. The values of Δ ec − ads G°(HUPD), Δ ec − ads S°(HUPD), Δ ec − ads H°(HUPD), and $${E}_{\mathrm{Pt}-{\mathrm{H}}_{\mathrm{UPD}}}$$ for UPD H in CF3SO3H are very similar to the analogous values obtained in aqueous H2SO4 and HClO4 solutions. The anion present in the electrolyte has a small impact on UPD H and influences the values of Δ ec − ads G°(HUPD) only over a narrow HUPD coverage range. The anion nature has practically no impact on the values of Δ ec − ads S°(HUPD), Δ ec − ads H°(HUPD), or $${E}_{\mathrm{Pt}-{\mathrm{H}}_{\mathrm{UPD}}}$$ .
PubDate: 2015-01-01

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