57Fe-Mössbauer spectroscopy and electrochemical activities of graphitic layer encapsulated iron electrocatalysts for the oxygen reduction reaction

Abstract

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Self‐Sacrificial Template Synthesis of a Nitrogen‐Doped Microstructured Carbon Tube as Electrocatalyst for Oxygen Reduction

“…The observed hyperfine magnetic field of sextet‐2 is 485 kOe which is close to 487 kOe. The γ‐Fe 2 O 3 is probably derived from the atmospheric oxidation after calcination, since Fe nanoparticles are prone to form a passivation layer of maghemite after being exposed in air. Sextet‐3 may assign to magnetic domains, such as magnetite (Fe 3 O 4 ) which is in accordance with the results of TEM and XRD (Figure b, Figure d).…”

N‐Doped Graphene Supported on Metal‐Iron Carbide as a Catalyst for the Oxygen Reduction Reaction: Density Functional Theory Study

“…For the encapsulatedF e-based catalyst, the roles of the Fe and Fe 3 Cp hases in the catalytic activity has been questioned as the inner nanoparticles are am ixture of severalp hases, that is, Fe and Fe 3 C. [19] The Fe 3 Cp hase is more efficient in the activation of the outer graphite layers toward the ORR than the Fe phase, which has been confirmed consistently by using both experiments [20,21] and at heoretical study. [22] Moreover,Ndoping in the graphitic layer has been shown to enhance the ORR activity of the Fe-based catalyst.…”

“…The Fe 3 C phase is more efficient in the activation of the outer graphite layers toward the ORR than the Fe phase, which has been confirmed consistently by using both experiments and a theoretical study . Moreover, N‐doping in the graphitic layer has been shown to enhance the ORR activity of the Fe‐based catalyst …”

“…[22] Moreover,Ndoping in the graphitic layer has been shown to enhance the ORR activity of the Fe-based catalyst. [13,[19][20][21][22] Recently,m any studies have explored the synthesis of ab imetallicc arbide encapsulatedi nN -doped graphene and showedt hat it displayed ab etter ORR activity and stability than the Fe 3 Cc atalyst. For instance, cobalt-iron carbide nanoparticles encapsulated by N-dopedg raphene nanosheets (NG/ CoFe carbide) have been synthesized.…”

Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

“…In previous work, a high-pressure approach was introduced to prepare graphitic-layer encapsulated Fe-containing nanoparticles (G@Fe) with well-defined hollow morphology and encapsulated structure [40]. Mössbauer spectroscopy has been used to recognize the encapsulated Fe components including a-Fe, c-Fe and Fe 3 C and surface trace of coordinated FeN x /C [41]. Through correlation examination between ORR activity and the content of Fe components, Fe 3 C as well as FeN x /C containing phases are proposed to most likely contribute to the ORR activity.…”