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

Journal Article · 26 November 2019 · Advanced Energy Materials

DOI: https://doi.org/10.1002/aenm.201903215 · OSTI ID:1581458

Khani, Hadi  ^[1]; Grundish, Nicholas S.  ^[1]; Wipf, David O.  ^[2]; Goodenough, John B.  ^[1]

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1. Texas Materials Institute and Materials Science and Engineering Program The University of Texas at Austin Austin TX 78712 USA
2. Department of Chemistry Mississippi State University Starkville MS 39762 USA

Abstract 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.

• Sponsoring Organization: USDOE
• OSTI ID: 1581458
• Journal Information: Advanced Energy Materials, Journal Name: Advanced Energy Materials Journal Issue: 1 Vol. 10; ISSN 1614-6832
• Publisher: Wiley Blackwell (John Wiley & Sons)Copyright Statement
• Country of Publication: Germany
• Language: English