scholarly journals Investigation of Earth-Abundant Oxygen Reduction Electrocatalysts for the Cathode of Passive Air-Breathing Direct Formate Fuel Cells

Catalysts ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 320 ◽  
Author(s):  
Francisca E. R. Oliveira ◽  
Nelson A. Galiote ◽  
Fabio H. B. Lima
Keyword(s):  
Fuel Cells ◽  
Oxygen Reduction ◽  
Limiting Current ◽  
Significant Activity ◽  
Air Breathing ◽  
X Ray ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Earth Abundant

The development of direct formate fuel cells encounters important obstacles related to the sluggish oxygen reduction reaction (ORR) and low tolerance to formate ions in Pt-based cathodes. In this study, electrocatalysts formed by earth-abundant elements were synthesized, and their activity and selectivity for the ORR were tested in alkaline electrolyte. The results showed that carbon-encapsulated iron-cobalt alloy nanoparticles and carbon-supported metal nitrides, characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD), do not present significant activity for the ORR, showing the same half-wave potential of Vulcan carbon. Contrarily, nitrogen-doped carbon, synthesized using imidazole as the nitrogen source, showed an increase in the half-wave potential, evidencing an influential role of nitrogen in the ORR electrocatalysis. The synthesis with the combination of Vulcan, imidazole, and iron or cobalt precursors resulted in the formation of nitrogen-coordinated iron (or cobalt) moieties, inserted in a carbon matrix, as revealed by X-ray absorption spectroscopy (XAS). Steady-state polarization curves for the ORR evidenced a synergistic effect between Fe and Co when these two metals were included in the synthesis (FeCo-N-C material), showing higher activity and higher limiting current density than the materials prepared only with Fe or Co. The FeCo-N-C material presented not only the highest activity for the ORR (approaching that of the state-of-the-art Pt/C) but also high tolerance to the presence of formate ions in the electrolyte. In addition, measurements with FeCo-N-C in the cathode of an passive air-breathing direct formate fuel cells, (natural diffusion of formate), showed peak power densities of 15.5 and 10.5 mW cm−2 using hydroxide and carbonate-based electrolytes, respectively, and high stability over 120 h of operation.

scholarly journals Modified Carbon Nanotubes: Surface Properties and Activity in Oxygen Reduction Reaction

Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1354
Author(s):  
Vera Bogdanovskaya ◽  
Inna Vernigor ◽  
Marina Radina ◽  
Vladimir Sobolev ◽  
Vladimir Andreev ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Zeta Potential ◽  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Surface Area ◽  
Surface Properties ◽  
Reduction Reaction ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave

In order to develop highly efficient and stable catalysts for oxygen reduction reaction (ORR) that do not contain precious metals, it is necessary to modify carbon nanotubes (CNT) and define the effect of the modification on their activity in the ORR. In this work, the modification of CNTs included functionalization by treatment in NaOH or HNO3 (soft and hard conditions, respectively) and subsequent doping with nitrogen (melamine was used as a precursor). The main parameters that determine the efficiency of modified CNT in ORR are composition and surface area (XPS, BET), hydrophilic–hydrophobic surface properties (method of standard contact porosimetry (MSP)) and zeta potential (dynamic light scattering method). The activity of CNT in ORR was assessed following half-wave potential, current density within kinetic potential range and the electrochemically active surface area (SEAS). The obtained results show that the modification of CNT with oxygen-containing groups leads to an increase in hydrophilicity and, consequently, SEAS, as well as the total (overall) current. Subsequent doping with nitrogen ensures further increase in SEAS, higher zeta potential and specific activity in ORR, reflected in the shift of the half-wave potential by 150 mV for CNTNaOH-N and 110 mV for CNTHNO3-N relative to CNTNaOH and CNTHNO3, respectively. Moreover, the introduction of N into the structure of CNTHNO3 increases their corrosion stability.

Cobalt decorated nitrogen-doped carbon bowls as efficient electrocatalysts for the oxygen reduction reaction

2020 ◽  
Vol 56 (32) ◽  
pp. 4488-4491 ◽  
Author(s):  
Haobin Zhong ◽  
Changwei Shi ◽  
Jiantao Li ◽  
Ruohan Yu ◽  
Qiang Yu ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Reduction Reaction ◽  
Nitrogen Doped ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Nitrogen Doped Carbon

Cobalt decorated nitrogen-doped carbon bowls (Co@NCB) demonstrate better ORR performance than Pt/C in terms of half-wave potential and stability.

Bimetallic ZIF derived Co nanoparticle anchored N-doped porous carbons for an efficient oxygen reduction reaction

2020 ◽  
Vol 7 (4) ◽  
pp. 946-952 ◽  
Author(s):  
Kaili Li ◽  
Daohao Li ◽  
Liangkui Zhu ◽  
Zhuangzhuang Gao ◽  
Qianrong Fang ◽  
...  
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
High Performance ◽  
Reduction Reaction ◽  
Porous Carbons ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Reaction Performance

A high-performance electrocatalytic material was derived from a new bimetallic ZIF precursor, exhibiting excellent oxygen reduction reaction performance with a half-wave potential (E1/2) of 0.849 V, superior to that of commercial Pt/C.

scholarly journals An ultra-dispersive, nonprecious metal MOF–FeZn catalyst with good oxygen reduction activity and favorable stability in acid

2021 ◽  
Vol 56 (14) ◽  
pp. 8600-8612
Author(s):  
Qing Zhao ◽  
Cheng Wang ◽  
Haifeng Wang ◽  
Jianlong Wang
Keyword(s):  
Oxygen Reduction ◽  
High Performance ◽  
Reduction Reaction ◽  
Graphitic Carbon ◽  
Potential Cycling ◽  
Onset Potential ◽  
Wave Potential ◽  
Reduction Activity ◽  
Half Wave Potential ◽  
Half Wave

AbstractDevelopment of the more stable nonprecious oxygen reduction reaction (ORR) catalyst is of great significance nowadays. Herein, a high-performance iron-doped integral uniform macrocyclic organic framework (MOF–FeZn) catalyst is synthesized through a combined hydrothermal and pyrolysis process, showing favorable ORR activity and stability in acid. This as-synthesized MOF–FeZn catalyst displays high porous and graphitic structures with sufficient catalytic active dopants of pyridinic N, Fe–N, pyrrolic N, graphitic N, making it a promising ORR candidate catalyst with high electrochemical stability. The onset potential, half-wave potential and limited diffusion current density of MOF–FeZn are 0.93 V @ 0.1 mA cm−2, 0.768 V@ 2.757 mA cm−2 and 5.5 mA cm−2, respectively, which are comparable to the state-of-the-art nonprecious catalyst and commercial Pt/C. ORR catalysis on MOF–FeZn follows the nearly four-electron path. What is more, MOF–FeZn can sustain the 10,000 cycles electrochemical potential cycling process in acid with the half-wave potential changed only 21 mV, superior to the reduction of 149 mV for Pt/C. The well-developed integral uniform structures, homogeneously dispersed carbides and nitrides protected by the highly graphitic carbon layers and the better agglomeration suppression of nanoparticles by the confined graphitic carbon layers on catalyst can significantly enhance the catalytic activity and stability of MOF–FeZn.

Half-wave potential-ph diagram for the parabenzoquinone system in n,n-dimethylformamide

1969 ◽  
Vol 2 (3) ◽  
pp. 123-132 ◽  
Author(s):  
J. Badoz-lambling ◽  
G. Demange-guerin
Keyword(s):  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave

Polarography of some coordination compounds of platinum. I. Hexammineplatinum (IV) and Tris(ethylenediamine)platinum(IV) ions

1955 ◽  
Vol 8 (2) ◽  
pp. 158 ◽  
Author(s):  
JR Hall ◽  
RA Plowman
Keyword(s):  
Potassium Chloride ◽  
Supporting Electrolyte ◽  
Platinum Metal ◽  
Potassium Nitrate ◽  
Diffusion Current ◽  
Polarographic Reduction ◽  
Wave Potential ◽  
Half Wave Potential ◽  
Half Wave ◽  
Continuous Discharge

The polarographic reduction of tris(ethylenediamine)platinum(IV) and the hexammineplatinum(IV) ions has been studied in potassium chloride, potassium nitrate, and potassium nitrate plus ammonia solutions. Both ions were reduced irreversibly producing similarly shaped waves, showing well-defined diffusion current regions corresponding to two-electron reductions of the complexes. A linear relationship existed between diffusion current and concentration within the range examined. In aqueous potassium chloride and potassium nitrate media, the waves contained slight inflexions at positions corresponding to one-electron additions. The phenomenon suggested the transient presence of platinum(III) ions, and indicated that the half-wave potential of the reduction of the complexes to the trivalent state was very close to the half-wave potential of the reduction from platinum(IV) to platinum(II). The values were so close together as to indicate the improbability of isolating the trivalent complexes. Gelatin enhanced the inflexion in the wave but shifted the wave in a more negative direction. An increased concentration of supporting electrolyte also shifted the wave to a more negative position. In all cases a continuous discharge began at about -1.3 V (v. S.C.E.). This discharge was so far removed from that of the potassium ions of the supporting electrolyte that it was attributed to the discharge of hydrogen. Since the initial reduction of the platinum complexes corresponded to a two-electron change, it can be represented by reduction to a tetrammine ion. It is postulated that at higher applied potentials (namely, -1.3 V v. S.C.E.) the reduction proceeded further, producing platinum metal. This platinum metal would be in an active state, insoluble in mercury, and being on the surface, would lower the overvoltage of hydrogen leading to its discharge at a more positive potential than on a pure mercury surface. This view was supported by the fact that gas bubbles were observed at the dropping electrode when a voltage greater than -1.3 V was applied to the electrode for some time. When ammonia was added to the supporting electrolyte, a wave, without an inflexion, and corresponding to an irreversible two-electron reduction, was obtained at more negative potentials. The bivalent tetrammineplatinum(II) and bis(ethylenediamine)platinum(II) ions also gave polarograms showing the continuous discharge of hydrogen.

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