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

Weiran Zheng; Mengjie Liu; Lawrence Yoon Suk Lee

doi:10.1021/acscatal.9b03790

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)

Research output: Journal article publication › Journal article › Academic research › peer-review

285 Citations (Scopus)

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 language	English
Pages (from-to)	81-92
Number of pages	12
Journal	ACS Catalysis
Volume	10
Issue number	1
DOIs	https://doi.org/10.1021/acscatal.9b03790
Publication status	Published - 3 Jan 2020

Keywords

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

ASJC Scopus subject areas

Catalysis
General Chemistry

More information

10.1021/acscatal.9b03790

http://hdl.handle.net/10397/100175

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@article{2889301046484bfb970f234fe9a457fc,

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

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.",

keywords = "Cobalt hydroxide, Electrochemical stability, In situ raman, in situ UV-vis, Oxygen evolution reaction, Spectroelectrochemistry, ZIF-67",

author = "Weiran Zheng and Mengjie Liu and Lee, {Lawrence Yoon Suk}",

note = "This work was supported by the Innovation and Technology Commission of Hong Kong and the Hong Kong Polytechnic University (grant number 1-BE0Y).",

year = "2020",

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doi = "10.1021/acscatal.9b03790",

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T1 - Electrochemical instability of metal-organic frameworks

T2 - In situ spectroelectrochemical investigation of the real active sites

AU - Zheng, Weiran

AU - Liu, Mengjie

AU - Lee, Lawrence Yoon Suk

N1 - This work was supported by the Innovation and Technology Commission of Hong Kong and the Hong Kong Polytechnic University (grant number 1-BE0Y).

PY - 2020/1/3

Y1 - 2020/1/3

N2 - 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.

AB - 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.

KW - Cobalt hydroxide

KW - Electrochemical stability

KW - In situ raman

KW - in situ UV-vis

KW - Oxygen evolution reaction

KW - Spectroelectrochemistry

KW - ZIF-67

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

Abstract

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