Surface site density and utilization of platinum group metal (PGM)-free Fe–NC and FeNi–NC electrocatalysts for the oxygen reduction reaction

Luo, Fengjian; Wagner, Stephan; Onishi, Ichiro; Selve, Sören; Li, Shuang; Ju, Wen; Wang, Huan; Steinberg, Julian; Thomas, Arne; Kramm, Ulrike I.; Strasser, Peter

doi:10.1039/d0sc03280h

Cited by 53 publications

(36 citation statements)

References 81 publications

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“…41 shows the atomic dispersion of Co and Fe centers). This implies that the isolated Fe sites are the dominating active species for ORR 40 . The high ORR performance of Fe sites is related to their stronger bonding affinity of Fe centers toward O 2 molecules 41 , 42 , which is in line with previous literature 19 , 43 .…”

Section: Resultsmentioning

confidence: 99%

Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts

et al. 2021

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Single-atom catalysts with maximum metal utilization efficiency show great potential for sustainable catalytic applications and fundamental mechanistic studies. We here provide a convenient molecular tailoring strategy based on graphitic carbon nitride as support for the rational design of single-site and dual-site single-atom catalysts. Catalysts with single Fe sites exhibit impressive oxygen reduction reaction activity with a half-wave potential of 0.89 V vs. RHE. We find that the single Ni sites are favorable to promote the key structural reconstruction into bridging Ni-O-Fe bonds in dual-site NiFe SAC. Meanwhile, the newly formed Ni-O-Fe bonds create spin channels for electron transfer, resulting in a significant improvement of the oxygen evolution reaction activity with an overpotential of 270 mV at 10 mA cm−2. We further reveal that the water oxidation reaction follows a dual-site pathway through the deprotonation of *OH at both Ni and Fe sites, leading to the formation of bridging O2 atop the Ni-O-Fe sites.

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Section: Resultsmentioning

confidence: 99%

Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts

et al. 2021

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“…This result suggests strong binding sites like those from SV to be present on Fe to a greater extent than NiNC. 45 Note that doped SV sites, or other binding sites of similar binding strength that we haven't considered, are not active sites for CO ! R, as they would be poisoned by CO. We rationalize the differences in dipole moments with the PDOS on s,p states of CO !…”

Section: The General Activity Volcano For Production Is Determined By Both the * And * Adsorption Energiesmentioning

confidence: 99%

Unified Mechanistic Understanding of CO2 Reduction to CO on Transition Metal and Single Atom Catalysts

Vijay

Ju²,

Brückner³

et al. 2021

Preprint

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CO is the simplest product from CO2 electroreduction (CO2R), but the identity and nature of its rate limiting step remains controversial. Here we investigate the activity of both transition metals (TMs) and metal-nitrogen doped carbon catalysts (MNCs), and a present unified mechanistic picture of CO2R to for both these classes of catalysts. By consideration of the electronic structure through a Newns-Andersen model, we find that on MNCs, like TMs, electron transfer to CO2 is facile, such that CO2 (g) adsorption is driven by adsorbate dipole-field interactions. Using density functional theory with explicit consideration of the interfacial field, we find CO2 * adsorption to generally be limiting on TMs, while MNCs can be limited by either CO2* adsorption or by the proton-electron transfer reaction to form COOH*. We evaluate these computed mechanisms against pH-dependent experimental activity measurements on CO2R to CO activity for Au, FeNC, and NiNC. We present a unified activity volcano that, in contrast to previous analyses, includes the decisive CO2* and COOH* binding strengths as well as the critical adsorbate dipole-field interactions. We furthermore show that MNC catalysts are tunable towards higher activity away from transition metal scaling, due to the stabilization of larger dipoles resulting from their discrete and narrow d-states. The analysis suggests two design principles for ideal catalysts: moderate CO2* and COOH* binding strengths as well as large dipoles on the CO2* intermediate. We suggest that these principles can be exploited in materials with similar electronic structure to MNCs, such as supported single-atom catalysts, molecules, and nanoclusters, 2D materials, and ionic compounds towards higher CO2R activity. This work captures the decisive impact of adsorbate dipole-field interactions in CO2R to CO and paves the way for computational-guided design of new catalysts for this reaction.

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“…Thus, construction of hierarchically porous carbon nanostructures with high surface area is an effective strategy to improve the utilization of M-N x site, thus promoting the ORR activity. [189][190][191][192][193][194][195][196][197][198] The template sacrificial strategy including hard template and soft template are common methods to create hierarchically porous M-N-C electrocatalysts. The template utilizes SiO 2 , 74,[199][200][201] SBA-15, 202 molten salts, 169 or Te nanowires 203 as sacrificial templates and small organic molecules, metal complexes or polymers as carbon/nitrogen precursors.…”

Section: Engineering Dense Active Sitesmentioning

confidence: 99%

Active site engineering of single-atom carbonaceous electrocatalysts for the oxygen reduction reaction

2021

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Surface site density and utilization of platinum group metal (PGM)-free Fe–NC and FeNi–NC electrocatalysts for the oxygen reduction reaction

Abstract: Pyrolyzed Iron-based precious group metal (PGM)-free nitrogen-doped single site carbon catalysts (Fe-NC) are possible alternatives to Platinum-based carbon catalysts for the oxygen reduction reaction (ORR). Bimetallic PGM-free M1M2-NC catalysts and...

Cited by 53 publications

References 81 publications

Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts

Mechanistic insight into the active centers of single/dual-atom Ni/Fe-based oxygen electrocatalysts

Unified Mechanistic Understanding of CO2 Reduction to CO on Transition Metal and Single Atom Catalysts

Active site engineering of single-atom carbonaceous electrocatalysts for the oxygen reduction reaction

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