Oxygen reduction in an acid medium: electrocatalysis by CoNPc(1,2) impregnated on a carbon black support; effect of loading and heat treatment

Biloul, A.; Coowar, F.; Contamin, O.; Scarbeck, G.; Savy, M.; Ham, D.M.W. van den; Riga, J.; Verbist, J.

doi:10.1016/0022-0728(93)80205-v

Cited by 24 publications

(21 citation statements)

References 27 publications

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“…In contrast to the Fe catalysts, for the Co catalysts the ORR activity increases about as the square root of the metal content (region 0-1 wt.%). It has been proposed by some authors that the Co active site consists of two Co atoms instead of only one [42,47]. However, such a hypothesis should result in an activity increasing faster than linearly with Co content (meaning a slope >1 in a log-log plane, Fig.…”

Section: Analysis Of the Increase In Orr Activity At Low Metal Contentmentioning

confidence: 96%

Average turn-over frequency of O2 electro-reduction for Fe/N/C and Co/N/C catalysts in PEFCs

Jaouen

Dodelet

2007

Electrochimica Acta

188

163

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Section: Analysis Of the Increase In Orr Activity At Low Metal Contentmentioning

confidence: 96%

Average turn-over frequency of O2 electro-reduction for Fe/N/C and Co/N/C catalysts in PEFCs

Jaouen

Dodelet

2007

Electrochimica Acta

188

163

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“…[15,61,62] The XRD and FT-IR results clearly showed that DAMCs derived from low-temperature pyrolysis possessed unique properties and preserved key features of the CoN4 structure, which acts as an active site for electrochemical ORR. [31][32][33][34] The Raman spectra of the as-prepared electrocatalysts showed D, G, and 2D bands without any additional variations (Figure S5, Supporting Information).…”

Section: Characterization Of Mwcnt-supported Phfcc Electrocatalystsmentioning

confidence: 99%

“…[27][28][29][30] To overcome the limitation of uncontrollable MN4 structures under high-temperature pyrolysis, processing MN4-macrocycle-based electrocatalysts at low-temperatures is a viable approach. [31][32][33][34] At low-temperatures, such as 300-600 °C, relatively moderate graphitization of the electrocatalyst system leads to sluggish electron transport behavior. This problem can be overcome using highly conductive and well-graphitized carbon materials, such as multi-walled carbon nanotubes (MWCNTs), whose delocalized sp 2 orbitals can be hybridized with highly-conjugated planar porphyrin and its analogs through strong π interactions.…”

Section: Introductionmentioning

confidence: 99%

“…[35][36][37][38][39][40] Although most reported non-precious catalysts have shown excellent ORR performance in basic media, [41] high-performance ORR activity in acidic media has been exclusively investigated using MN4-centered electrocatalysts obtained from pristine MN4 macrocycles. [18][19][20][21][31][32][33][34] Recent studies of cobalt and iron-based MN4 macrocycle complexes alone have shown better electrocatalytic ORR performance, with subsequent studies focusing on their homo-and heterobimetallic complexes to maintain both activity and stability. [18][19][20][21][42][43][44][45][46] Compared with recently reported bimetallic systems derived from two different metal precursors, a single molecular complex composed of heterobimetals in close proximity, resulting in a synergistic effect, is highly desirable for a facile oxygen reduction mechanism, similar to the natural ORR conducted by cytochrome c oxidase.…”

Section: Introductionmentioning

confidence: 99%

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Synergistic Dual‐Atom Molecular Catalyst Derived from Low‐Temperature Pyrolyzed Heterobimetallic Macrocycle‐N4 Corrole Complex for Oxygen Reduction

Samireddi

Aishwarya

Shown

et al. 2021

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layer are a major drawback to their cost-effective commercialization. To date, although platinum-group metal-based catalysts have been recognized as the best-performing ORR electrocatalysts, their future use as cathode catalysts is limited by scarcity and high costs, meaning that alternative economic cathode catalysts are greatly needed. [1] Among tremendous research efforts toward developing non-precious electrocatalysts, transition-metal-based metal-N4 (MN4) macrocyclic compounds have emerged as promising non-platinum group metal electrocatalysts after the pioneering breakthrough of Jasinski in 1964, who reported a cobalt phthalocyaninebased electrocatalyst. [2] Recent studies have reported a broad range of macrocyclic MN4 centers, such as Co and Fecoordinated porphyrins, phthalocyanines, corrins, and corroles, that possess promising non-precious metal active catalytic sites for the ORR. [2][3][4][5] A common feature of these macrocyclic MN4 systems is a single transition metal atom with biomimetic ligands, and with the maintenance of these single-metal-atom MN4 active sites as electrocatalysts being the most important factor in improving the ORR. Therefore, the use of these N4 macrocyclic complexes for developing A heterobimetallic corrole complex, comprising oxygen reduction reaction (ORR) active non-precious metals Co and Fe with a corrole-N4 center (PhFCC), is successfully synthesized and used to prepare a dual-atom molecular catalyst (DAMC) through subsequent low-temperature pyrolysis. This low-temperature pyrolyzed electrocatalyst exhibited impressive ORR performance, with onset potentials of 0.86 and 0.94 V, and half-wave potentials of 0.75 and 0.85 V, under acidic and basic conditions, respectively. During potential cycling, this DAMC displayed half-wave potential losses of only 25 and 5 mV under acidic and alkaline conditions after 3000 cycles, respectively, demonstrating its excellent stability. Single-cell Nafion-based proton exchange membrane fuel cell performance using this DAMC as the cathode catalyst showed a maximum power density of 225 mW cm −2 , almost close to that of most metal-N4 macrocycle-based catalysts. The present study showed that preservation of the defined CoN4 structure along with the cocatalytic Fe-Cx site synergistically acted as a dual ORR active center to boost overall ORR performance. The development of DAMC from a heterobimetallic CoN4macrocyclic system using low-temperature pyrolysis is also advantageous for practical applications.

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“…Based on Mössbauer and X-ray absorption spectroscopy, van Veen and his collaborators proposed that the chelates metal-N 4 moiety is retained in the heat treatment, and actually binds to the carbon support [41,42,42,80,81] During the 1990's, other groups backed van Veen's hypothesis of a MeN 4 resembling site. Savy and Savinell et al prepared Fe or Co napthophthalocyanines [82][83][84] and porphyrins [85,86] with various loadings and different carbon blacks, they characterized their catalysts with Infrared (IR) spectroscopy, X-ray photoelectron spectroscopy (XPS) and rotating disk electrode (RDE) and suggested that the Me-N 4 moiety remains intact when heat-treated up to 500 °C. The group of Dodelet, through time-of-flight secondary-ion mass spectrometry (ToF SIMS), initially proposed that the nature of the catalytic sites involved a coordination between the transition metal ion, nitrogen, and carbon support, in the form of MeN x C y + .…”

Section: Metal-free Cn X -Sitesmentioning

confidence: 99%

Degradation studies of Me-N-C catalysts for the oxygen reduction reaction in fuel cells

Μαρτιναίου¹

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The increasing demand forrenewable energy along with the requirement of decreasing CO2 emissions is a major challenge for the scientific community. Fuel cells are among the most promising electrochemical devices because of their low operating temperature and high power density. The main advantage of a fuel cell is that electrical power can be produced continuously as long as the fuel supply is provided. Another important advantage is high efficiency. The efficiency of fuel cells is superior to that of combustion engines, particularly at low loads, which makes low-temperature fuel cells (0―100 °C) attractive for automotive propulsion. State of the art catalyst for the anode as well as the cathode is typically based on platinum-supported on carbon. However, the platinum catalyst alone would account for 38-56% of the stack cost [1]. Thus the higher efficiency, in comparison to combustion engines, comes with a higher price that makes the commercialization not competitive now. As a large quantity of the precious metal is required to catalyse the oxygen reduction reaction (ORR), current research is focused on this reaction and especially on the development of alternative non-precious metal catalysts (NPMC). In order for these catalysts to be a commercially viable solution for replacing platinum-based catalysts, they should meet two criteria, improving both activity and stability of these catalysts. Despite, several milestones that have been achieved regarding the activity of these catalysts [2– 5], stability is still relatively poor in comparison to platinum-based systems. This dissertation focuses on the investigation of the stability of non-precious metal catalysts for oxygen reduction reaction mainly in acidic media for application in Proton Exchange Membrane Fuel Cells (PEMFCs) and Direct Methanol Fuel Cells (DMFCs). Α part of this study also deals with performance determination of NPMC in alkaline media, regarding their application in Alkaline Fuel Cells (AFCs). The electrochemical tests were performed with a Rotating Disk Electrode technique. Stability refers to the ability of a system to maintain performance at constant current (or voltage) conditions, while durability refers to the ability to maintain performance following a voltage cycling. First, a systematic study on the impact of the metal centre on durability was conducted. Thirteen MeN-C catalysts were examined with a Start/ Stop (SSC) durability protocol in the potential range of 1.0 V – 1.5 V. Raman spectroscopy was performed before and after the durability tests and a correlation between electrochemical evaluation and Raman spectroscopy in this potential region was found. The carbon oxidation is related to the disintegration of active MeN4 sites that might be initiated by both: the oxidation of the surrounding graphene sheets and by a displacement of the metal out of the N4 plane and this was evidenced by a decrease in the D3 band. Furthermore, a novel synthesis protocol was developed in our group and a Fe-N-C catalyst was optimized with the addition of sulfur(S) in the precursor. With respect to activity the best-off S-added catalyst and the S-free one were then examined for durability under a Load Cycle (LC) protocol (0.6– 1.0 V) in alkaline media. A modification of both catalysts with ionic liquid (IL) was introduced by the group of Professor B. J.M. Etzold within a cooperation framework. The durability of the modified S-free catalyst was found superior to the durability of the non-modified catalyst. In the case of the Sadded catalyst, the IL modification did not further improve its durability. Finally, a third synthesis approach was developed, leading to an active Fe-N-C catalyst also with sulfur in the precursor. The stability of this catalyst was investigated in a DMFC within a research stay abroad project in collaboration with Professor S. Specchia from Politecnico di Torino and subsequently examined by post mortem Mössbauer spectroscopy. This catalyst was further evaluated with a Load Cycle durability protocol and post mortem Raman spectroscopy in our laboratories.

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Oxygen reduction in an acid medium: electrocatalysis by CoNPc(1,2) impregnated on a carbon black support; effect of loading and heat treatment

Cited by 24 publications

References 27 publications

Average turn-over frequency of O2 electro-reduction for Fe/N/C and Co/N/C catalysts in PEFCs

Average turn-over frequency of O2 electro-reduction for Fe/N/C and Co/N/C catalysts in PEFCs

Synergistic Dual‐Atom Molecular Catalyst Derived from Low‐Temperature Pyrolyzed Heterobimetallic Macrocycle‐N4 Corrole Complex for Oxygen Reduction

Degradation studies of Me-N-C catalysts for the oxygen reduction reaction in fuel cells

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