Highly Active Cobalt‐Based Electrocatalysts with Facile Incorporation of Dopants for the Oxygen Evolution Reaction

Moon, Gun‐hee; Yu, Mingquan; Chan, Candace K.; Tüysüz, Harun

doi:10.1002/ange.201813052

Cited by 44 publications

(18 citation statements)

References 44 publications

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“…As displayed in Fig. 1b , a number of bright spots are clearly observed, in which Fe/Mn atomic pairs are randomly distributed on the surface of N-doped carbon as highlighted by red cycles, attributed to heavy Fe, Mn than light N, C atoms 35 . In order to make it clearer whether Mn–N 4 is adjacent to Fe–N 4 , the atomic-resolution HAADF-STEM of Fe–N–C and Mn–N–C catalysts have been additionally carried out.…”

Section: Resultsmentioning

confidence: 95%

Regulating Fe-spin state by atomically dispersed Mn-N in Fe-N-C catalysts with high oxygen reduction activity

et al. 2021

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As low-cost electrocatalysts for oxygen reduction reaction applied to fuel cells and metal-air batteries, atomic-dispersed transition metal-nitrogen-carbon materials are emerging, but the genuine mechanism thereof is still arguable. Herein, by rational design and synthesis of dual-metal atomically dispersed Fe,Mn/N-C catalyst as model object, we unravel that the O2 reduction preferentially takes place on FeIII in the FeN4 /C system with intermediate spin state which possesses one eg electron (t2g4eg1) readily penetrating the antibonding π-orbital of oxygen. Both magnetic measurements and theoretical calculation reveal that the adjacent atomically dispersed Mn-N moieties can effectively activate the FeIII sites by both spin-state transition and electronic modulation, rendering the excellent ORR performances of Fe,Mn/N-C in both alkaline and acidic media (halfwave positionals are 0.928 V in 0.1 M KOH, and 0.804 V in 0.1 M HClO4), and good durability, which outperforms and has almost the same activity of commercial Pt/C, respectively. In addition, it presents a superior power density of 160.8 mW cm−2 and long-term durability in reversible zinc–air batteries. The work brings new insight into the oxygen reduction reaction process on the metal-nitrogen-carbon active sites, undoubtedly leading the exploration towards high effective low-cost non-precious catalysts.

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Section: Resultsmentioning

confidence: 95%

Regulating Fe-spin state by atomically dispersed Mn-N in Fe-N-C catalysts with high oxygen reduction activity

et al. 2021

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“…), but it is still unclear that the promoting effect of OER is from the complex material composition or from the in situ generated thin layers of hydroxide/ oxyhydroxide. Thus, developing an universal and facile approach to obtain the catalysts with highly efficient and well‐defined structure is highly desirable, which not only can satisfy the industrial demands mentioned above, but also can well explore the active sites and mechanism of catalysts …”

Section: Introductionmentioning

confidence: 99%

Physically Adsorbed Metal Ions in Porous Supports as Electrocatalysts for Oxygen Evolution Reaction

Liu

Shen

et al. 2020

Adv Funct Materials

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Developing highly efficient and earth‐abundant electrocatalysts for the oxygen evolution reaction (OER) is significantly important for water‐splitting. Here, for the first time it is reported that the physically adsorbed metal ions (PAMI) in porous materials can be served as highly efficient OER electrocatalysts, which provides a universal PAMI method to develop electrocatalysts. This PAMI method can be applied to almost all porous supports, including graphene, carbon nanotubes, C3N4, CaCO3, and porous organic polymers and all the systems exhibit excellent OER performance. In particular, the as‐synthesized Co0.7Fe0.3CB exhibits a small overpotential of 295 mV and 350 mV at the current density of 10 mA cm−2 and 100 mA cm−2, respectively, which exceeds commercial 40 wt% IrO2/CB and most reported non‐noble metal‐based OER catalysts. Moreover, the mass activity of Co0.7Fe0.3CB reaches 643.4 A g−1 at the overpotential of 320 mV, which is nearly 4.7 times higher than that of 40 wt% IrO2/CB. In addition, the advanced ex situ and in situ synchrotron X‐ray characterizations are carried out to unravel the PAMI synthetic process. In short, this PAMI method will break the conversional understanding, i.e., the most OER catalysts are synthesized chemically, because the new PAMI method does not require any chemical synthesis, which therefore opens a new avenue for the development of OER electrocatalysts.

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“…The sites are a result of the formation of mixed iron-cobalt (oxy)hydroxides. As studied by some of us, the rigid structure of Co 3 O 4 obtained by nanocasting was less susceptible to iron contamination 43,53 than the less crystalline material studied by Smith et al 5 Cyclic voltammograms recorded after SI-SECM experiments showed that the redox peak I a at ~1.25 V is vanishing (Figure S8). This could be explained by an anodic shift due to electronic effects by the substitution of Co II by Fe III or by an irreversible oxidation of some Co II sites to Co III during SI-SECM.…”

Section: Time-dependent Si-secm Experimentsmentioning

confidence: 88%

“…The identification of Co IV species is very challenging even with spectroscopic techniques. 5,14,[42][43][44] In contrast to Eq. (1)-( 3), the different redox peaks in the voltammogram have also been described as transition of solely Co II to Co III , where the segmentation results from different structural motifs.…”

Section: Cyclic Voltammetrymentioning

confidence: 92%

“…Iron (intentionally added or existed as contamination in the electrolyte) is known to have a beneficial effect on the OER activity of cobalt oxides. 3,5,43 The possible influence of contamination by Fe ions from decomposed redox mediator or impurities of the hydroxide solution has to be considered as an alternative explanation for different reaction rates. Smith et al 5 identified two independent reaction sites on cobalt-iron oxides that catalyze the OER with distinct reaction rates.…”

Section: Time-dependent Si-secm Experimentsmentioning

confidence: 99%

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Coulometric Titration of Active Sites at Mesostructured Cobalt Oxide Spinel by Surface Interrogation Mode of Scanning Electrochemical Microscopy

Lorenz

Tüysüz

et al. 2020

J. Phys. Chem. C

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Cobalt-based transition metal oxides are promising candidates for the oxygen evolution reaction.However, a complex interplay between the catalyst crystal structures and material morphologies as well as the surface reactions hampers a comprehensive understanding of the electrocatalytic oxygen evolution reaction at those materials. Here, we investigate the amount and reactivity of specific surface sites of a mesostructured cobalt oxide spinel powder by surface interrogation mode of scanning electrochemical microscopy (SI-SECM). The powder material was supplied in cavity-microelectrodes and efficiently titrated with an Fe(II)-triethanolamine redox mediator generated at a gold microelectrode in alkaline electrolyte. Thus, quantification of different surface sites was achieved and their reactivity showed dependence on the cobalt oxidation state.Titration experiments after adjustable time delays with respect to the generation of the different surface sites indicated that these surface sites are active for the oxygen evolution reaction. Kinetic analysis revealed two pseudo-first order decay constants that were related to fast and slow surface sites for the oxygen evolution reaction. Rate constants were determined for potentials where predominantly a mixed-valence Co III/IV state might be present as most active species. These results expand the great potential of the surface interrogation mode on studying the reaction kinetics of distinct surface sites for practically relevant powdered, non-precious metal catalysts to address a highly relevant challenge in electrocatalysis.

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Highly Active Cobalt‐Based Electrocatalysts with Facile Incorporation of Dopants for the Oxygen Evolution Reaction

Cited by 44 publications

References 44 publications

Regulating Fe-spin state by atomically dispersed Mn-N in Fe-N-C catalysts with high oxygen reduction activity

Regulating Fe-spin state by atomically dispersed Mn-N in Fe-N-C catalysts with high oxygen reduction activity

Physically Adsorbed Metal Ions in Porous Supports as Electrocatalysts for Oxygen Evolution Reaction

Coulometric Titration of Active Sites at Mesostructured Cobalt Oxide Spinel by Surface Interrogation Mode of Scanning Electrochemical Microscopy

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