Durable and Efficient Hollow Porous Oxide Spinel Microspheres for Oxygen Reduction

Hao Wang, Ruiping Liu, Yutao Li, Xujie Lü, Qi Wang, Shiqiang Zhao, Kunjie Yuan, Zhiming Cui, Xiang Li, Sen Xin, Ru Zhang, Ming Lei, Zhiqun Lin

Research output: Contribution to journalArticlepeer-review

185 Scopus citations

Abstract

Transition metal oxide catalysts with high oxygen reduction activity and durability are highly desirable for use in fuel cells and metal-air batteries. Herein we report, for the first time, the oxygen reduction activity of hollow porous spinel AB2O4 microspheres, where A = Zn2+ and B = Mn3+ and/or Co3+ (i.e., ZnMnxCo2−xO4). Among them, ZnMnCoO4 (x = 1) microspheres exhibit the best oxygen reduction activity with a half-wave-potential only 50 mV lower than that of the Pt/C counterpart and an excellent durability in the alkaline solution. Importantly, the electronic transition of Co3+ ions from low-spin state in commercial Co3O4 catalyst to a mixed high-spin and low-spin state in ZnMnCoO4 catalyst was found to weaken the Co3+-OH bond and facilitate the O2−/OH displacement. The density functional theory calculation substantiated that ZnMnCoO4 displayed a more favorable binding energy with O2 and oxygenated species, thereby enabling the fast reaction kinetics in the oxygen reduction reaction process. Transition metal oxide catalysts with high oxygen reduction activity and durability are highly desirable as they promise new opportunities as alternatives to rare noble-metal catalysts for use in fuel cells and metal-air batteries. However, transition metal oxides often possess high overpotentials. In this paper, we report the crafting of a family of Co3+-based spinel oxides (AB2O4: A = Zn2+ and B = Mn3+ and/or Co3+) and the subsequent exploration of their use as catalysts in the oxygen reduction reaction (ORR) by scrutinizing the correlation between the electronic structure of Co3+ ions and the resulting ORR performance. Among them, ZnMnCoO4 (x = 1) microspheres where Mn and Co ions are located at the B site of spinel AB2O4 were found to exhibit the best oxygen reduction activity, with a half-wave-potential only 50 mV lower than that of the Pt/C counterpart and an excellent durability in the alkaline solution. The electronic transition of Co3+ ions from low-spin state in commercial Co3O4 catalyst to a mixed high-spin and low-spin state in ZnMnCoO4 catalyst was found to weaken the Co3+-OH bond and facilitate the O2−/OH displacement. The oxygen reduction reaction performance of the hollow porous oxide spinel microspheres was investigated. The ZnMnCoO4 possessed a high onset potential of 1.00 V and an outstanding durability in the alkaline solution. The electronic transition of Co3+ ions was found to weaken the Co3+-OH bond and facilitate the O2−/OH displacement. Thus, it may offer promising potential for use as an effective catalyst with high oxygen reduction activity and durability in fuel cells and metal-air batteries, among other applications.

Original languageEnglish
Pages (from-to)337-348
Number of pages12
JournalJoule
Volume2
Issue number2
DOIs
StatePublished - 21 Feb 2018

Bibliographical note

Publisher Copyright:
© 2017 Elsevier Inc.

Keywords

  • ZnMnCoO
  • bond strength
  • oxygen reduction reaction
  • spinel
  • stability

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