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. 2023 May 31;28(11):4464.
doi: 10.3390/molecules28114464.

Synthesis of Ketjenblack Decorated Pillared Ni(Fe) Metal-Organic Frameworks as Precursor Electrocatalysts for Enhancing the Oxygen Evolution Reaction

Thi Hai Yen Beglau  1 , Lars Rademacher  1 , Robert Oestreich  1 , Christoph Janiak  1
Affiliations

Synthesis of Ketjenblack Decorated Pillared Ni(Fe) Metal-Organic Frameworks as Precursor Electrocatalysts for Enhancing the Oxygen Evolution Reaction

Thi Hai Yen Beglau et al. Molecules. .

Abstract

Metal-organic frameworks (MOFs) have been investigated with regard to the oxygen evolution reaction (OER) due to their structure diversity, high specific surface area, adjustable pore size, and abundant active sites. However, the poor conductivity of most MOFs restricts this application. Herein, through a facile one-step solvothermal method, the Ni-based pillared metal-organic framework [Ni2(BDC)2DABCO] (BDC = 1,4-benzenedicarboxylate, DABCO = 1,4-diazabicyclo[2.2.2]octane), its bimetallic nickel-iron form [Ni(Fe)(BDC)2DABCO], and their modified Ketjenblack (mKB) composites were synthesized and tested toward OER in an alkaline medium (KOH 1 mol L-1). A synergistic effect of the bimetallic nickel-iron MOF and the conductive mKB additive enhanced the catalytic activity of the MOF/mKB composites. All MOF/mKB composite samples (7, 14, 22, and 34 wt.% mKB) indicated much higher OER performances than the MOFs and mKB alone. The Ni-MOF/mKB14 composite (14 wt.% of mKB) demonstrated an overpotential of 294 mV at a current density of 10 mA cm-2 and a Tafel slope of 32 mV dec-1, which is comparable with commercial RuO2, commonly used as a benchmark material for OER. The catalytic performance of Ni(Fe)MOF/mKB14 (0.57 wt.% Fe) was further improved to an overpotential of 279 mV at a current density of 10 mA cm-2. The low Tafel slope of 25 mV dec-1 as well as a low reaction resistance due to the electrochemical impedance spectroscopy (EIS) measurement confirmed the excellent OER performance of the Ni(Fe)MOF/mKB14 composite. For practical applications, the Ni(Fe)MOF/mKB14 electrocatalyst was impregnated into commercial nickel foam (NF), where overpotentials of 247 and 291 mV at current densities of 10 and 50 mA cm-2, respectively, were realized. The activity was maintained for 30 h at the applied current density of 50 mA cm-2. More importantly, this work adds to the fundamental understanding of the in situ transformation of Ni(Fe)DMOF into OER-active α/β-Ni(OH)2, β/γ-NiOOH, and FeOOH with residual porosity inherited from the MOF structure, as seen by powder X-ray diffractometry and N2 sorption analysis. Benefitting from the porosity structure of the MOF precursor, the nickel-iron catalysts outperformed the solely Ni-based catalysts due to their synergistic effects and exhibited superior catalytic activity and long-term stability in OER. In addition, by introducing mKB as a conductive carbon additive in the MOF structure, a homogeneous conductive network was constructed to improve the electronic conductivity of the MOF/mKB composites. The electrocatalytic system consisting of earth-abundant Ni and Fe metals only is attractive for the development of efficient, practical, and economical energy conversion materials for efficient OER activity.

Keywords: Ketjenblack; electrocatalysis; iron; metal-organic frameworks (MOFs); nickel; oxygen evolution reaction (OER).

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Conflict of interest statement

The authors declare no conflict of interest.

Figures

Scheme 1
Scheme 1
Schematic illustration of the process used for the synthesis of the NiDMOF/mKB and Ni(Fe)DMOF/mKB composites and the transformation of the MOF into metal oxide-hydroxides with the retention of the MOF morphology. For the nickel (oxy)hydroxides, the unit cells of the crystal structures are given in polyhedral mode.
Figure 1
Figure 1
The PXRD patterns of NiDMOF, NiDMOF/mKB14, Ni(Fe)DMOF, Ni(Fe)DMOF/mKB14, and mKB. The simulated PXRD pattern of NiDMOF was obtained from CCDC no. 802892. The first five reflexes at 2θ = 8.2°, 9.4°, 11.7°, 12.4°, and 16.6° corresponded to the 100, 001, 110, 101 and 200 planes, respectively.
Figure 2
Figure 2
(a) Nitrogen sorption isotherms at 77 K (filled symbols adsorption; empty symbols desorption) and (b) the pore size distribution of NiDMOF, NiDMOF/mKB14, Ni(Fe)DMOF, Ni(Fe)DMOF/mKB14, and mKB.
Figure 3
Figure 3
SEM images of (a) NiDMOF/mKB14, (b) Ni(Fe)DMOF/mKB14, (c) EDX scanning element mapping for nickel, nitrogen and iron for Ni(Fe)DMOF/mKB14, and (d) the EDX spectrum with the composition for the selected mapping area of Ni(Fe)DMOF/mKB14.
Figure 4
Figure 4
High-resolution XPS spectra of (a) Ni 2p and (b) Fe 2p of Ni(Fe)DMOF/mKB14.
Figure 5
Figure 5
(a) Polarization curves (LSV) operated at a scan rate of 5 mV s−1 with the iR correction. (b) Tafel plots, (c) corresponding overpotentials (columns) and Tafel slopes (red dots) at 10 mA cm−2, (d) raw data of Nyquist plots at 1.5 V vs. RHE (points) and fitting to an equivalent circuit model (Figure S16, Supplementary Materials) (solid line) from the EIS test of mKB, NiDMOF, NiDMOF/mKB7, NiDMOF/mKB14, NiDMOF/mKB22, and NiDMOF/mKB34.
Figure 6
Figure 6
(a) Polarization curves (LSV) operated at a scan rate of 5 mV s−1 with iR correction, (b) Tafel plots, (c) corresponding overpotentials (columns) and Tafel slopes (red dots) at 10 mA cm−2, (d) raw data of Nyquist plots at 1.5 V vs. RHE (points) and the fitting data of an equivalent circuit model (Figure S16, Supplementary Materials) (solid line) from the EIS test of mKB, RuO2, NiDMOF, Ni(Fe)DMOF, NiDMOF/mKB14, and Ni(Fe)DMOF/mKB14.
Figure 7
Figure 7
(a) Linear sweep voltammetry (LSV) curves at a scan rate of 5 mV s−1 with iR correction. (b) Chronopotentiometric curves for 30 h at a current density of 50 mA cm−2 of the NiFe-DMOF/mKB14 loaded on nickel foam (NF) and bare NF for comparison in a 1.0 mol L−1 KOH solution.
Figure 8
Figure 8
(a) PXRD patterns of the experimental Ni(Fe)DMOF/mKB14 and derived-Ni(Fe)DMOF/mKB14 after 24 h in 1 mol L−1 KOH and simulated NiDMOF (CCDC Nr. 802892). Reflections from β–Ni(OH)2 (●, ICDD: 14-0117), α–Ni(OH)2 (#, ICDD: 38-0715), β–NiOOH (◆, ICDD: 06-0141), and γ–NiOOH (♥, ICDD: 06-0075). (b) FTIR of Ni(Fe)DMOF and Ni(Fe)DMOF/mKB14 and its derived products in 1 mol L−1 KOH after 24 h. (c) SEM images of the derived-Ni(Fe)DMOF/mKB14 material (large image) and neat Ni(Fe)DMOF/mKB14 (small image). (d) Nitrogen sorption isotherms at 77 K (filled symbols adsorption, empty symbols desorption isotherm) and pore size distribution (small graph) of derived-Ni(Fe)DMOF and derived-Ni(Fe)DMOF/mKB14 after 24 h in 1 mol L−1 KOH.
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References

    1. Lianos P. Review of recent trends in photoelectrocatalytic conversion of solar energy to electricity and hydrogen. Appl. Catal. B. 2017;210:235–254. doi: 10.1016/j.apcatb.2017.03.067. - DOI
    1. Chu S., Cui Y., Liu N. Opportunities and challenges for a sustainable energy future. Nat. Mater. 2017;16:16–22. doi: 10.1038/nmat4834. - DOI - PubMed
    1. Wang J., Zhang H., Wang X. Recent Methods for the Synthesis of Noble-Metal-Free Hydrogen-Evolution Electrocatalysts: From Nanoscale to Sub-nanoscale. Small Methods. 2017;1:1700118. doi: 10.1002/smtd.201700118. - DOI
    1. Shrivastav V., Sundriyal S., Goel P., Kaur H., Tuteja S.K., Vikrant K., Kim K.-H., Tiwari U.K., Deep A. Metal-organic frameworks (MOFs) and their composites as electrodes for lithium battery applications: Novel means for alternative energy storage. Coord. Chem. Rev. 2019;393:48–78. doi: 10.1016/j.ccr.2019.05.006. - DOI
    1. Lee Y., Suntivich J., May K.J., Perry E.E., Shao-Horn Y. Synthesis and Activities of Rutile IrO2 and RuO2 Nanoparticles for Oxygen Evolution in Acid and Alkaline Solutions. J. Phys. Chem. Lett. 2012;3:399–404. doi: 10.1021/jz2016507. - DOI - PubMed