Oxygen reduction reaction (ORR) in acidic media is investigated at various potentials a thin-film rotating disk electrode (TF-RDE) configuration using electrochemical impedance spectroscopy (EIS). The ionomer-free and ionomer-containing catalyst layers are composed of Pt black carbon-supported catalysts different metal loadings (5 20 wt%). simplest EI spectrum consisting an arc or semi-circle obtained high with layers. most complex frequency (HF) two semi-circles observed the mixed...

Nitrogen-doped carbon (N/C) and graphene (N/G) were synthesized by the established conventional heat-treatment method, incorporation of nitrogen into matrix was confirmed CHN analysis, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy. Electrochemical impedance (EIS) prepared catalysts in argon-saturated 0.1 M KOH performed a three-electrode rotating disk electrode (RDE) configuration. The capacitance derived from low-frequency region EIS patterns used to estimate effective density...

Synthesis of shape-controlled nanoparticles precious metals with defined size is well-established in the literature and control over shape achieved using surfactants capping agents. However, a clean surface without impurities required for realistic applications. In present investigation, palladium nanocubes are synthesized poly(vinylpyrrolidone) potassium bromide. A novel method cleaning nanoparticle surface, i.e., treatment tert-butylamine reported. For comparison, part untreated sample...

Shape-controlled Pt nanoparticles (cubic, tetrahedral, and cuboctahedral) are synthesized using stabilizers capping agents. The cleaned thoroughly electrochemically characterized in acidic (0.5 M H2SO4 0.1 HClO4) alkaline (0.1 NaOH) electrolytes, their features compared to that of polycrystalline Pt. Even with less than 100% shape-selectivity the truncation at edges corners as shown by ex-situ TEM analysis, voltammetric shape-controlled correlate very well respective single-crystal surfaces,...

Oxygen reduction reaction (ORR) is investigated on bulk PdO-based catalysts (oxides of Pd and Pd3Co) in oxygen-saturated 0.1 M HClO4 to establish the role surface oxides adsorbed hydrogen activity product selectivity (H2O/H2O2). The initial voltammetric features suggest that are inactive toward ORR. evolution ORR voltammograms potential-dependent H2O2 generation PdO catalyst gradual parallel situ phase below ∼0.4 V underpotential deposition (Hupd) region; confirmed from X-ray photoelectron...

An unsupported Cu-Pt core-shell catalyst is prepared by a transmetalation reaction between copper and Pt2+ ions, bimetallic alloy simultaneous reduction reaction. Both catalysts are subjected to electrochemical leaching without further treatment their characteristics ORR activities compared that of standard Pt black catalyst. Potential cycling in 0.1 M HClO4 0.5 H2SO4 shows the highly stable features show it purely on surface. The surface area much higher than black. When loading electrode...

Hydrogen uptake at 250 °C, PH2 > 15 bar and release 320, 350 °C by MgH2 mixed with 10 wt % rGO alleviates the incubation period (slow kinetics) encountered during hydrogen pure MgH2. Ball milling establishes Mg–C interactions (∼283 eV) in these nanocomposites through electron-transfer from Mg to π* of C weakens C–C π bond. These persist upon subsequent release. change hybridization sp2 sp3, aiding (C–H). On release, H releases C–H, electrons are donated back Mg. This electron back-donation...

Electrochemical impedance spectroscopy is used to investigate the charge-transfer and mass-transfer processes of VO2+/VO2 + (V4+/V5+) redox species across carbon-modified glassy carbon disk electrode/electrolyte interface. The features EIS patterns depend on potential, concentrations mass-transport conditions at With starting electrolyte containing either only V4+ or V5+ species, shows a straight line capacitor feature, as no oxidation reduction reaction take place measured open circuit...

Carbon-supported Pd and Pd3Co catalysts have been electrochemically characterized in 0.1 M HClO4 solution we found that both were unstable. On repeated potential cycling, the electrochemical surface area of decreases oxygen reduction reaction (ORR) activity suffers. To stabilize atoms catalysts, deposited Pt using adsorbed hydrogen on catalytically active sites. The : ratio Pt-coated suggests half-a-monolayer coverage (two required for reducing a Pt2+ ion). catalyst obtained from simple...

Hydrogen evolution reaction (HER) are investigated on Pt, Pd, and MoS2 in a 0.5 M H2SO4 electrolyte rotating disk electrode (RDE) configuration the temperature range of 285-335 K. The is temperature-sensitive all three catalyst surfaces at their respective overpotential ranges. kinetic parameters (activation enthalpy (ΔH#), free energy activation (ΔG#), pre-exponential factor (Af)) toward HER obtained from Arrhenius Eyring relations, overall kinetics analyzed. ΔH# for strong function case...

The rate of electron-transfer reactions, irrespective whether electrochemical or electrocatalytic, is universally explained on the basis Butler-Volmer (B-V) theory. charge-transfer coefficient (α) obtained typically in range 0.0-1.0, and 0.6 ± 0.1 for oxygen reduction reaction (ORR) Pt, which subject present investigation. Alternatively, α can be estimated from derivative change Gibbs free energy activation (ΔG#) with respect to overpotential (η) has unreasonably high value 1.1 0.2. origin...

Abstract Poly (vinylidene fluoride) (PVDF) is widely utilized for its unique pyro and piezoelectric properties related to electro‐active β ‐PVDF. In the past few decades, methods of producing ‐PVDF by mechanical stretching non‐polar α have been extensively documented. The aim present study understand correlation between phase behavior β‐PVDF obtained directly from spin‐coating, stretch‐induced transformation α‐PVDF. effect thermal annealing in‐plane anisotropy on spin‐coated PVDF...

Using the hydride formation property of Pd for removal strongly-adsorbed impurities from nanoparticle surfaces.

Reconstruction and dissolution of shape-controlled Pt nanoparticles in acidic electrolytes.

The shape control of Pd nanoparticles is investigated using chloride (Cl(-)) ions as capping agents in an aqueous medium the temperature range 60-100 °C. With weakly adsorbing and strongly etching Cl(-) ions, oxygen plays a crucial role control. experimental factors considered are concentration agents, reaction time atmosphere. Thus, various shapes with high selectivity can be synthesized. Moreover, removal from nanoparticle surface easier than that Br(-) (moderately etching) I(-) (strongly...

Transport of redox species (VO2+/VO2+, V2+/V3+, Ti3+/Ti4+, and Fe2+/Fe3+) across the electrode/electrolyte interface is investigated in a thin-film rotating disk electrode configuration using electrochemical impedance spectroscopy (EIS). The transport features depend on constituents catalyst layer rate constant reaction. On Nafion-free porous electrodes, semi-infinite linear finite are observed under static hydrodynamic conditions electrode, respectively. Depending reaction, an equivalent...

A method to estimate the electrochemical active site density of carbon and nitrogen-doped using phosphomolybdate as a probe is proposed. The complete rejection background current in AC voltammetry offers better density.