Graphitic‐Shell Encapsulation of Metal Electrocatalysts for Oxygen Evolution, Oxygen Reduction, and Hydrogen Evolution in Alkaline Solution

Developing highly efficient, cost effective, and environmentally friendly electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is of interest for sustainable and clean energy technologies, including metal–air batteries and f...

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Bibliographic Details
Published in:Advanced energy materials 2020-01, Vol.10 (1), p.n/a
Main Authors: Khani, Hadi, Grundish, Nicholas S., Wipf, David O., Goodenough, John B.
Format: Article
Language:English
Subjects:
Binary alloys
Binary system
Clean energy
Electrocatalysts
Electrochemical activation
Encapsulation
Energy technology
Exfoliation
Fuel cells
Graphene
graphite‐encapsulated transition metals
heterogeneous catalysis
hydrogen evolution reaction
Hydrogen evolution reactions
Iron
Nanoparticles
Nickel
Oxidation
oxygen evolution reaction
Oxygen evolution reactions
oxygen reduction reaction
Oxygen reduction reactions
Sol-gel processes
Ternary alloys
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Summary:Developing highly efficient, cost effective, and environmentally friendly electrocatalysts for the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) is of interest for sustainable and clean energy technologies, including metal–air batteries and fuel cells. In this work, the screening of electrocatalytic activities of a series of single metallic iron, cobalt, and nickel nanoparticles and their binary and ternary alloys encapsulated in a graphitic carbon shell toward the OER, ORR, and HER in alkaline media is reported. Synthesis of these compounds proceeds by a two‐step sol–gel and carbothermal reduction procedure. Various ex situ characterizations show that with harsh electrochemical activation, the graphitic shell undergoes an electrochemical exfoliation. The modified electronic properties of the remaining graphene layers prevent their exfoliation, protect the bulk of the metallic cores, and participate in the electrocatalysis. The amount of near‐surface, higher‐oxidation‐state metals in the as‐prepared samples increases with electrochemical cycling, indicating that some metallic nanoparticles are not adequately encased within the graphite shell. Such surface oxide species provide secondary active sites for the electrocatalytic activities. The Ni–Fe binary system gives the most promising results for the OER, and the Co–Fe binary system shows the most promise for the ORR and HER. Screening of electrocatalytic activities of a series of graphite‐encapsulated single metallic iron, cobalt, and nickel nanoparticles and their binary and ternary alloys toward the oxygen evolution reaction (OER), oxygen reduction reaction (ORR), and hydrogen evolution reaction (HER) in alkaline media reveal that the Ni–Fe binary system gives the most promising results for the OER, and the Co–Fe binary systems have the most promise for the ORR and HER reactions.
ISSN:1614-6832
1614-6840
DOI:10.1002/aenm.201903215