Electrochemical instability of metal-organic frameworks: In situ spectroelectrochemical investigation of the real active sites

Weiran Zheng, Mengjie Liu, Lawrence Yoon Suk Lee*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

94 Scopus citations

Abstract

Despite recent attempts using metal-organic frameworks (MOFs) directly as electrocatalysts, the electrochemical stability of MOFs and the role of in situ-formed species during electrochemistry are elusive. Using in situ spectroelectrochemistry, we present herein a comprehensive discussion on the structural and morphological evolution of MOFs (zeolitic imidazolate framework-67, ZIF-67) during both cyclic voltammetry and amperometry. Dramatic morphological changes exposing electron-accessible Co sites are evident. The intense conversion from tetrahedral Co sites in ZIF-67 to tetrahedral α-Co(OH)2 and octahedral β-Co(OH)2, and the formation of their corresponding oxidized forms (CoOOH), is observed during both the electrochemical treatments. Subsequent oxygen evolution reaction suggests the CoOOH produced from α/β-Co(OH)2 as the dominating active sites, not the metal nodes of ZIF-67. Specifically, the CoOOH from α-Co(OH)2 is most active (turnover frequency = 0.59 s-1) compared to that from β-Co(OH)2 (0.06 s-1). Our study demonstrates the importance of examining the electrochemical stability of MOFs for electrocatalyst design.

Original languageEnglish
Pages (from-to)81-92
Number of pages12
JournalACS Catalysis
Volume10
Issue number1
DOIs
StatePublished - 3 Jan 2020
Externally publishedYes

Keywords

  • Cobalt hydroxide
  • Electrochemical stability
  • In situ raman
  • Oxygen evolution reaction
  • Spectroelectrochemistry
  • ZIF-67
  • in situ UV-vis

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