Elucidating Oxygen Reduction Active Sites in Pyrolyzed Metal–Nitrogen Coordinated Non-Precious-Metal Electrocatalyst Systems

Tylus, Urszula; Jia, Qingying; Strickland, Kara; Ramaswamy, Nagappan; Serov, Alexey; Atanassov, Plamen; Mukerjee, Sanjeev

doi:10.1021/jp500781v

Cited by 492 publications

(507 citation statements)

References 75 publications

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“…Additionally, it is important to point out the higher open circuit potential for both materials at the more alkaline pH, which is an indicator of an electrolyte where carbon materials have a higher catalytic effect. This is expected due to the higher concentration of hydroxyl species, which have been demonstrated to be an important participant in the oxygen reduction reaction for other carbon-based materials [51]. In the RRDE setup, it is also possible to measure the amount of hydrogen peroxide produced during the ORR, as this peroxide is further reduced to water in the platinum ring that the probe possesses.…”

Section: Rrde Resultsmentioning

confidence: 99%

Carbon-Based Air-Breathing Cathodes for Microbial Fuel Cells

et al. 2016

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Abstract:A comparison between different carbon-based gas-diffusion air-breathing cathodes for microbial fuel cells (MFCs) is presented in this work. A micro-porous layer (MPL) based on carbon black (CB) and an activated carbon (AC) layer were used as catalysts and applied on different supporting materials, including carbon cloth (CC), carbon felt (CF), and stainless steel (SS) forming cathode electrodes for MFCs treating urine. Rotating ring disk electrode (RRDE) analyses were done on CB and AC to: (i) understand the kinetics of the carbonaceous catalysts; (ii) evaluate the hydrogen peroxide production; and (iii) estimate the electron transfer. CB and AC were then used to fabricate electrodes. Half-cell electrochemical analysis, as well as MFCs continuous power performance, have been monitored. Generally, the current generated was higher from the MFCs with AC electrodes compared to the MPL electrodes, showing an increase between 34% and 61% in power with the AC layer comparing to the MPL. When the MPL was used, the supporting material showed a slight effect in the power performance, being that the CF is more powerful than the CC and the SS. These differences also agree with the electrochemical analysis performed. However, the different supporting materials showed a bigger effect in the power density when the AC layer was used, being the SS the most efficient, with a power generation of 65.6 mW·m −2 , followed by the CC (54 mW·m −2 ) and the CF (44 mW·m −2 ).

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Section: Rrde Resultsmentioning

confidence: 99%

Carbon-Based Air-Breathing Cathodes for Microbial Fuel Cells

et al. 2016

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“…Recent studies indicate that the iron atoms are coordinated by four nitrogens in a square planar arrangement, where the nitrogen atoms belong to pyridine rings embedded in graphene planes. 7,8 Oxygen reduction is part of numerous biological cycles and accomplished through enzymatic catalysis. As these natural processes are not constrained by any artificial boundaries, the problem of a limited space and thus of insufficient active site density does not exist.…”

Section: ■ Introductionmentioning

confidence: 99%

Effects of Axial Coordination of the Metal Center on the Activity of Iron Tetraphenylporphyrin as a Nonprecious Catalyst for Oxygen Reduction

Chlistunoff

Sansiñena

2014

J. Phys. Chem. C

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Effects of axial coordination of the metal center on oxygen reduction catalyzed by iron tetraphenylporphyrin have been studied using spectroelectrochemical and rotating ring disk electrode techniques. Among numerous ligands studied, the strongest complexation of the metal center was observed for imidazole and some substituted imidazole ligands. Around 300 mV positive shift of the oxygen reduction potential in 0.5 M H2SO4 was observed when the catalyst support (high surface area carbon Vulcan XC72) was impregnated with polyvinylimidazole. A smaller 200 mV shift of the reduction potential was recorded when graphene modified with 1-(3-aminopropyl)imidazole was used as the catalyst support instead of Vulcan. In both cases, the catalyst selectivity for four-electron reduction was also substantially improved. The effects of iron complexation on oxygen reduction kinetics and mechanism result from both a positive shift of the potential of the first porphyrin reduction and an increase of the electron density on the iron center through the so-called “push effect”. The observed phenomena are discussed in relation to heat-treated Fe/N/C catalysts for oxygen reduction.

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“…2.1 Å, related to the Fe-Fe and Co-Co first coordination shell. This is ascribed to the presence of carbon-encapsulated FeCo nanoparticles in the sample [36]. Also, it is observed a "shoulder" centered at 1.5 Å for both absorption edges, and this can be related to the coordination of Fe or Co and atoms with low-atomic numbers, such as N or O.…”

Section: Electrocatalyst Characterizationmentioning

confidence: 81%

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

2018

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Abstract: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.

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Elucidating Oxygen Reduction Active Sites in Pyrolyzed Metal–Nitrogen Coordinated Non-Precious-Metal Electrocatalyst Systems

Cited by 492 publications

References 75 publications

Carbon-Based Air-Breathing Cathodes for Microbial Fuel Cells

Carbon-Based Air-Breathing Cathodes for Microbial Fuel Cells

Effects of Axial Coordination of the Metal Center on the Activity of Iron Tetraphenylporphyrin as a Nonprecious Catalyst for Oxygen Reduction

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

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