scholarly journals Temperature dependence of the kinetics of oxygen reduction on carbon-supported pt nanoparticles

2008 ◽  
Vol 73 (6) ◽  
pp. 641-654 ◽  
Author(s):  
Nevenka Elezovic ◽  
Biljana Babic ◽  
Nedeljko Krstajic ◽  
Snezana Gojkovic ◽  
Ljiljana Vracar
Keyword(s):  
Temperature Dependence ◽  
Oxygen Reduction ◽  
Current Density ◽  
Pt Nanoparticles ◽  
Reduction Reaction ◽  
Hydrogen Electrode ◽  
Rate Determining Step ◽  
Current Densities ◽  
Kinetics Of ◽  
Mechanism Of The Reaction

The temperature dependence of oxygen reduction reaction (ORR) was studied on highly dispersed Pt nanoparticles supported on a carbon cryo-gel. The specific surface area of the support was 517 m2 g-1, the Pt particles diameter was about 2.7 nm and the loading of the catalyst was 20 wt.%. The kinetics of the ORR at the Pt/C electrode was examined in 0.50 mol dm-3 HClO4 solution in the temperature range from 274 to 318 K. At all temperatures, two distinct E-log j regions were observed; at low current densities with a slope of -2.3RT/F and at high current densities with a slope of -2.3?2RT/F. In order to confirm the mechanism of oxygen reduction previously suggested at a polycrystalline Pt and a Pt/Ebonex nanostructured electrode, the apparent enthalpies of activation at selected potentials vs. the reversible hydrogen electrode were calculated in both current density regions. Although ?H ?a,1 > ?H ?a,h , it was a,1 a, h found that the enthalpies of activation at the zero Galvani potential difference were the same and hence it could be concluded that the rate-determining step of the ORR was the same in both current density regions. The synthesized Pt/C catalyst showed a small enhancement in the catalytic activity for ORR in comparison to the polycrystalline Pt, but no change in the mechanism of the reaction.

scholarly journals Oxygen reduction at platinum nanoparticles supported on carbon cryogel in alkaline solution

2007 ◽  
Vol 72 (7) ◽  
pp. 699-708 ◽  
Author(s):  
N.R. Elezovic ◽  
B.M. Babic ◽  
LJ.M. Vracar ◽  
N.V. Krstajic
Keyword(s):  
Particle Size ◽  
Oxygen Reduction ◽  
Alkaline Solution ◽  
Reduction Reaction ◽  
Rotating Disc ◽  
Rate Determining Step ◽  
Naoh Solution ◽  
Orr Kinetics ◽  
Carbon Cryogel ◽  
Current Densities

The oxygen reduction reaction was investigated in 0.1 M NaOH solution, on a porous coated electrode formed of Pt particles supported on carbon cryogel. The Pt/C catalyst was characterized by the X-ray diffraction (XRD), transmission electron microscopy (TEM) and cyclic voltammetry techniques. The results demonstrated a successful reduction of Pt to metallic form and homogenous Pt particle size distribution with a mean particle size of about 2.7 nm. The ORR kinetics was investigated by linear sweep polarization at a rotating disc electrode. The results showed the existence of two E - log j regions, usually referred to polycrystalline Pt in acid and alkaline solution. At low current densities (lcd), the Tafel slope was found to be close to -2.3RT/F, while at high current densities (hcd) it was found to be close to -2?2.3RT/F. It is proposed that the main path in the ORR mechanism on Pt particles was the direct four-electron process, with the transfer of the first electron as the rate determining step. If the activities are expressed through the specific current densities, a small enhancement of the catalytic activity for Pt/C was observed compared to that of polycrystalline Pt. The effect of the Pt particle size on the electrocatalysis of oxygen reduction was ascribed to the predominant (111) facets of the platinum crystallites. .

scholarly journals Conducting Copper(I/II)-Metallopolymer for the Electrocatalytic Oxygen Reduction Reaction (ORR) with High Kinetic Current Density

Polymers ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1002 ◽  
Author(s):  
Sait Elmas ◽  
Wesley Beelders ◽  
Xun Pan ◽  
Thomas Nann
Keyword(s):  
Fuel Cell ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Noble Metals ◽  
Reduction Reaction ◽  
Rotating Disk Electrode ◽  
Potential Candidate ◽  
Hydrogen Electrode ◽  
Electrocatalytic Oxygen Reduction ◽  
Current Densities

The oxygen reduction reaction (ORR) is still the most research-intensive aspect of a fuel cell. The sluggish kinetics of the electrocatalysts toward the ORR requires large amounts of platinum to be used as cathode material, which calls for alternatives to replace or minimize the amount of the noble metals used. This study describes the synthesis and complete characterization of a copper metallopolymer (Cu MP) based on a conducting polymer (CP) and single-site catalytic centers for the electrocatalytic ORR. The copper (II) catalyst, embedded in a redox-active and conducting polymeric environment, was pursued as a potential candidate to replace noble metals in fuel cell applications. Performance studies at a rotating disk electrode (RDE) showed that the metallopolymer exhibited a direct four-electron reduction at potentials between −150 and −350 mV vs. the reversible hydrogen electrode (RHE) and high kinetic current densities of over 22.62 mA/cm2. The kinetic current densities obtained at the Cu MP electrode outperformed most of the reported state-of-the art electrocatalysts toward the ORR. Further analysis of the Cu/CP hybrid revealed the copper being largely reduced to the oxidation state +I.

ZIF-67 Derived Cu-Doped Electrocatalyst for Oxygen Reduction Reaction

2020 ◽  
Vol 18 (2) ◽  
Author(s):  
M. Daarain Haider ◽  
Naseem Iqbal ◽  
Syed Aun M. Rizvi ◽  
Tayyaba Noor ◽  
Saadia Hanif ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Current Density ◽  
Electrochemical Impedance ◽  
Metal Organic Framework ◽  
Reduction Reaction ◽  
Electrode System ◽  
Alkaline Media ◽  
Hydrogen Electrode ◽  
Onset Potential

Abstract In the present study, the catalytic activity of copper-loaded cobalt-based metal–organic framework (ZIF-67) composites was studied for their electrochemical oxygen reduction reaction (ORR). The Cu-ZIF-67 composite was prepared by the solvothermal method. After pyrolysis under argon atmosphere at 700 °C, the composite was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and Fourier transform infrared spectroscopy (FTIR). The electrochemical activity of the composites was tested for ORR in 0.1 M alkaline media using the three-electrode system by cyclic voltammetry (CV), Tafel plots, and electrochemical impedance spectroscopy (EIS). The composites showed variable activity with a current density of 1.32 mA cm−2 at 0.71 V (versus reversible hydrogen electrode (RHE)) onset potential for 70 wt% Cu-ZIF-67, 7.5 mA cm−2 at 0.82 V (versus RHE) onset potential for 50 wt% Cu-ZIF-67, and 11.85 mA cm−2 at 0.85 V (versus RHE) for 30% Cu-ZIF-67. The increasing ratio of the ZIF-67 effect can be attributed to the increased activity of ZIF-67 with the synergistic effect of Cu toward increased current density.

Synthesis of unused-wood-derived C-Fe-N catalysts for oxygen reduction reaction by heteroatom doping during hydrothermal carbonization and subsequent carbonization in nitrogen atmosphere

2021 ◽  
Vol 379 (2209) ◽  
Author(s):  
Yasuto Goto ◽  
Yuta Nakayasu ◽  
Hiroya Abe ◽  
Yuto Katsuyama ◽  
Takashi Itoh ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Current Density ◽  
Low Cost ◽  
Hydrothermal Carbonization ◽  
Reduction Reaction ◽  
Nitrogen Atmosphere ◽  
Hydrogen Electrode ◽  
Efficient Manner ◽  
And Storage

There is an urgent need to develop renewable sources of energy and use existing resources in an efficient manner. In this study, in order to improve the utilization of unused biomass and develop green processes and sustainable technologies for energy production and storage, unused Douglas fir sawdust (SD) was transformed into catalysts for the oxygen reduction reaction. Fe and N were doped into SD during hydrothermal carbonization, and the N- and Fe-doped wood-derived carbon (Fe/N/SD) was carbonized in a nitrogen atmosphere. After the catalyst had been calcined at 800°C, its showed the highest current density (−5.86 mAcm −2 at 0.5 V versus reversible hydrogen electrode or RHE) and E onset value (0.913 V versus RHE). Furthermore, its current density was higher than that of Pt/C (20 wt% Pt) (−5.66 mA cm −2 @0.5 V versus RHE). Finally, after 50 000 s, the current density of sample Fe/N/SD (2 : 10 : 10) remained at 79.3% of the initial value. Thus, the synthesized catalysts, which can be produced readily at a low cost, are suitable for use in various types of energy generation and storage devices, such as fuel cells and air batteries. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)’.

Pt Distribution- Controlled Ni-Pt Nanocrystals via Alcohol Reduction Technique for Oxygen Reduction Reaction

2021 ◽  
Author(s):  
Kaneyuki Taniguchi ◽  
Jhon Lehman Cuya Huaman ◽  
Dausuke Iwata ◽  
Shun Yokoyama ◽  
Takatoshi Matsumoto ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Pt Nanoparticles ◽  
Cost Benefit ◽  
Reduction Reaction ◽  
Reduction Technique ◽  
Co Poisoning ◽  
Transition Elements ◽  
Poisoning Effect ◽  
Alcohol Reduction

Alloying Pt with transition elements as electrodes in fuel cells has been proposed to solve the CO poisoning effect besides cost-benefit. Consequently, the use of Ni-Pt nanoparticles (NPs) has been...

scholarly journals Mixed Lithium and Sodium Ion Aprotic DMSO Electrolytes for Oxygen Reduction on Au and Pt Studied by DEMS and RRDE

2021 ◽  
Author(s):  
M. Hegemann ◽  
P. P. Bawol ◽  
A. Köllisch-Mirbach ◽  
H. Baltruschat
Keyword(s):  
Oxygen Reduction ◽  
Product Distribution ◽  
Reduction Reaction ◽  
Mixed Electrolytes ◽  
Peroxide Formation ◽  
Pt Electrode ◽  
Rate Determining Step ◽  
Differential Electrochemical Mass Spectrometry ◽  
Redox Couples ◽  
Pt Electrodes

AbstractIn order to advance the development of metal-air batteries and solve possible problems, it is necessary to gain a fundamental understanding of the underlying reaction mechanisms. In this study we investigate the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER, from species formed during ORR) in Na+ containing dimethyl sulfoxide (DMSO) on poly and single crystalline Pt and Au electrodes. Using a rotating ring disk electrode (RRDE) generator collector setup and additional differential electrochemical mass spectrometry (DEMS), we investigate the ORR mechanism and product distribution. We found that the formation of adsorbed Na2O2, which inhibits further oxygen reduction, is kinetically favored on Pt overadsorption on Au. Peroxide formation occurs to a smaller extent on the single crystal electrodes of Pt than on the polycrystalline surface. Utilizing two different approaches, we were able to calculate the heterogeneous rate constants of the O2/O2− redox couple on Pt and Au and found a higher rate for Pt electrodes compared to Au. We will show that on both electrodes the first electron transfer (formation of superoxide) is the rate-determining step in the reaction mechanism. Small amounts of added Li+ in the electrolyte reduce the reversibility of the O2/O2− redox couples due to faster and more efficient blocking of the electrode by peroxide. Another effect is the positive potential shift of the peroxide formation on both electrodes. The reaction rate of the peroxide formation on the Au electrode increases when increasing the Li+ content in the electrolyte, whereas it remains unaffected on the Pt electrode. However, we can show that the mixed electrolytes promote the activity of peroxide oxidation on the Pt electrode compared to a pure Li+ electrolyte. Overall, we found that the addition of Li+ leads to a Li+-dominated mechanism (ORR onset and product distribution) as soon as the Li+ concentration exceeds the oxygen concentration. Graphical abstract

scholarly journals Superior FexN electrocatalyst derived from 1,1′-diacetylferrocene for oxygen reduction reaction in alkaline and acidic media

2020 ◽  
Vol 9 (1) ◽  
pp. 843-852
Author(s):  
Hunan Jiang ◽  
Jinyang Li ◽  
Mengni Liang ◽  
Hanpeng Deng ◽  
Zuowan Zhou
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Current Density ◽  
Active Sites ◽  
Reduction Reaction ◽  
Alkaline Media ◽  
Acidic Media ◽  
Onset Potential ◽  
Acidic And Alkaline Media ◽  
The Stability

AbstractAlthough Fe–N/C catalysts have received increasing attention in recent years for oxygen reduction reaction (ORR), it is still challenging to precisely control the active sites during the preparation. Herein, we report FexN@RGO catalysts with the size of 2–6 nm derived from the pyrolysis of graphene oxide and 1,1′-diacetylferrocene as C and Fe precursors under the NH3/Ar atmosphere as N source. The 1,1′-diacetylferrocene transforms to Fe3O4 at 600°C and transforms to Fe3N and Fe2N at 700°C and 800°C, respectively. The as-prepared FexN@RGO catalysts exhibited superior electrocatalytic activities in acidic and alkaline media compared with the commercial 10% Pt/C, in terms of electrochemical surface area, onset potential, half-wave potential, number of electrons transferred, kinetic current density, and exchange current density. In addition, the stability of FGN-8 also outperformed commercial 10% Pt/C after 10000 cycles, which demonstrates the as-prepared FexN@RGO as durable and active ORR catalysts in acidic media.

Comparative Cathodic Behavior of ~9% Cr and Plain Steel Reinforcement in Concrete

CORROSION ◽  
2012 ◽  
Vol 68 (4) ◽  
pp. 045003-1-045003-10 ◽  
Author(s):  
M. Akhoondan ◽  
A.A. Sagüés
Keyword(s):  
Carbon Steel ◽  
Oxygen Reduction ◽  
Current Density ◽  
Surface Condition ◽  
Corrosion Current ◽  
Reduction Reaction ◽  
Cathodic Current Density ◽  
Cathodic Current ◽  
Steel Rebar ◽  
Cathodic Region

The extent of the oxygen reduction reaction in concrete was evaluated for ~9% Cr rebar approaching the ASTM A1035 specification and compared to that of conventional carbon steel rebar, at ages of up to ~1 year. Cathodic strength was measured by the cathodic current density developed at −0.35 V vs. copper/copper sulfate (Cu/CuSO4 [CSE]) and −0.40 VCSE in cyclic cathodic potentiodynamic polarization tests, both in the as-received condition with mill scale and with scale removed by glass bead surface blasting. In both conditions the ~9% Cr alloy was a substantially weaker cathode, by a factor of several fold, than carbon steel. Within each material, the surface-blasted condition yielded also much lower cathodic current density than the as-received condition. For a small anode-large cathode system with a given anode polarization function, and no important oxygen reduction concentration polarization, the corrosion current was projected to be significantly lower if the cathodic region were ~9% Cr instead of plain steel rebar with comparable surface condition. There was strong correlation between the charge storage capability of the interface and the extent of cathodic reaction of oxygen. The result cannot be ascribed solely to differences in effective surface area between the different materials and conditions.

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