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Structural transformation of metal–organic frameworks and identification of electrocatalytically active species during the oxygen evolution reaction under neutral condition

DOI: 10.1039/D2QI02436E DOI Help

Authors: Xiaoqiang Liang (Xi’an Polytechnic University) , Sen Wang (Xi’an Polytechnic University) , Jingyu Feng (Imperial College London; Queen Mary University of London) , Zhen Xu (Imperial College London; University of Cambridge) , Zhenyu Guo (Imperial College London) , Hui Luo (Imperial College London) , Feng Zhang (Harbin Normal University) , Wen Chen (Beijing Spacecrafts) , Lei Feng (Beijing Spacecrafts) , Chengan Wan (Beijing Spacecrafts) , Maria-Magdalena Titirici (Imperial College London)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Inorganic Chemistry Frontiers

State: Published (Approved)
Published: April 2023
Diamond Proposal Number(s): 28663

Abstract: Electrocatalytic oxygen evolution reaction (OER) under neutral or near-neutral conditions has attracted research interest due to its environmental friendliness and economic sustainability in comparison with currently available acidic and alkaline conditions. However, it is challenging to identify electrocatalytically active species in the OER procedure under neutral environments due to non-crystalline forms of catalysts. Crystalline metal-organic framework (MOF) materials could provide novel insights into electrocatalytical active species because of their well-defined structures. In this study, we synthesized two isostructural two-dimensional (2D) MOFs [Co(HCi)2(H2O)2·2DMF]n (Co-Ci-2D) and [Ni(HCi)2(H2O)2·2DMF]n (Ni-Ci-2D) (H2Ci = 1H-indazole-5-carboxylic acid, DMF = N, N-Dimethyl-formamide) to investigate their OER performance in a neutral environment. Our results indicate that Co-Ci-2D holds a current density of 3.93 mA cm-2 at 1.8 V vs. RHE and a OER durability superior to the benchmark catalyst IrO2. Utilizing the advantages of structural transformation of MOF materials which are easier to characterize and analyze compared to ill-defined amorphous materials, we found out that a mononuclear coordination compound [Co(HCi)2(H2O)4] (Co-Ci-mono-A) and its isomer (Co-Ci-mono-B) were proven to be active species of Co-Ci-2D in the neutral OER process. For Ni-Ci-2D, mononuclear coordination compounds similar to structures of the cobalt material (Ni-Ci-mono-A and Ni-Ci-mono-B) together with NiHPO4 formed by the precipitation were confirmed as active species for the neutral OER catalysis. Additionally, the difference in OER activities between Co-Ci-2D and Ni-Ci-2D, approximately one order of magnitude, originates primarily from the opposite tendency of bond length changes in coordination octahedron after being treated by the PBS solution. These findings contribute to a better comprehension of the OER procedure in the neutral media.

Subject Areas: Chemistry, Materials, Energy

Instruments: I20-EDE-Energy Dispersive EXAFS (EDE)

Other Facilities: BM28 at ESRF

Added On: 13/04/2023 08:45

Discipline Tags:

Energy Storage Energy Physical Chemistry Catalysis Chemistry Materials Science Chemical Engineering Engineering & Technology Metal-Organic Frameworks Metallurgy Organometallic Chemistry

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS)