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

TY - JOUR

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 - Publisher Copyright: © 2019 American Chemical Society.

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 - Oxygen evolution reaction

KW - Spectroelectrochemistry

KW - ZIF-67

KW - in situ UV-vis

UR - http://www.scopus.com/inward/record.url?scp=85076240099&partnerID=8YFLogxK

U2 - 10.1021/acscatal.9b03790

DO - 10.1021/acscatal.9b03790

M3 - 文章

AN - SCOPUS:85076240099

SN - 2155-5435

VL - 10

SP - 81

EP - 92

JO - ACS Catalysis

JF - ACS Catalysis

IS - 1

ER -