Spinel-type NiCo2O4 with abundant oxygen vacancies as a high-performance catalyst for the oxygen reduction reaction

• Published in: International journal of hydrogen energy Vol. 44; no. 42; pp. 23775 - 23783
• Main Authors: Lim, Dongwook, Kong, Hyungseok, Lim, Chaewon, Kim, Namil, Shim, Sang Eun, Baeck, Sung-Hyeon
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 03-09-2019
• Subjects: NiCo2O4; Oxygen reduction reaction; Oxygen vacancy; Spinel structure; NiCo2O4; Spinel structure; Oxygen reduction reaction; Oxygen vacancy
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2019.07.091

Spinel-type nickel cobaltite with numerous oxygen vacancies is successfully synthesized by hydrothermal and thermal reduction using hydrogen. The effects of oxygen vacancies on the electrochemical activity and stability for the oxygen reduction reaction are investigated. The prepared catalyst displays significantly enhanced oxygen reduction reaction (ORR) catalytic performance under alkaline conditions, which is comparable to that of commercial Pt/C. The oxygen-deficient NiCo2O4 exhibits a very high limiting current density of −5.44 mA cm−2 with onset and half-wave potentials of 0.93 and 0.78 V versus the reversible hydrogen electrode (RHE), respectively. Additionally, it shows excellent durability and resistance to methanol. The enhanced ORR activity and stability of the catalyst can be ascribed to the synergistic effects of the relatively large electrochemical surface area, more exposed active sites, and good electrical conductivity derived from abundant oxygen vacancies.
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•NiCo2O4 nanoparticles with oxygen vacancies were synthesized by a hydrothermal method followed by mild H2 reduction.•The H2-treated NiCo2O4 exhibited a low overpotential and substantial long-term stability for oxygen reduction reaction.•This outstanding ORR performance and stability can be attributed to the improved physicochemical properties by H2 treatment.