Amorphous Ni1–xFex Oxyhydroxide Nanosheets with Integrated Bulk and Surface Iron for a High and Stable Oxygen Evolution Reaction

  • Birhanu Bayissa Gicha
    Birhanu Bayissa Gicha
    Department of Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea
  • Lemma Teshome Tufa
    Lemma Teshome Tufa
    Department of Applied Chemistry, Adama Science and Technology University, Adama 888, Ethiopia
  • Youngeun Choi
    Youngeun Choi
    Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea
  • , and 
  • Jaebeom Lee*
    Jaebeom Lee
    Department of Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea
    Department of Chemical Engineering and Applied Chemistry, Chungnam National University, Daejeon 34134, Republic of Korea
    *Email: [email protected]
    More by Jaebeom Lee
Cite this: ACS Appl. Energy Mater. 2021, 4, 7, 6833–6841
Publication Date (Web):June 22, 2021
https://doi.org/10.1021/acsaem.1c00955
Copyright © 2021 American Chemical Society
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Abstract

Ni-based electrocatalysts, especially with Fe, are attractive electrocatalysts for oxygen evolution reaction (OER) due to their exhilarating surface properties and anticipated synergistic effect. Herein, amorphous Ni1–xFex oxyhydroxide nanosheets (x: 0, 0.25, 0.50, 0.75, and 1) with integrated bulk and surface Fe were synthesized by facile electrodeposition as an active and stable electrocatalyst for OER. Different ratios of Fe and Ni precursors were deposited on nickel foam cathodically for bulk Fe (FeB) embodiment. Then, surface Fe (FeS) was integrated through anodic cycling from Fe-containing KOH. Benefiting from the amorphous structure and integration between FeB and FeS, high activity and stability were achieved. Accordingly, FeB+S-NIFE25 has demonstrated the highest OER activity, with the lowest overpotential of 300 mV at a current density of 50 mA cm–2, a Tafel slope as low as 30 mV dec–1, and robust stability exceeding 100 h for continuous oxygen generation while the same material (NIFE25) in the absence of FeS, has demonstrated relatively a higher overpotential of 340 mV and a Tafel slope of 65 mV dec–1. Computation simulation also calculated that the NIFEX composites containing both FeB and FeS demonstrated weak binding energies enhancing OH density at the reaction interface facilitating O2 generation. It is probable that the synergy between FeB and FeS coupled with an amorphous structure induces higher OER activity and stability and can be readily applied to generate cheap and clean hydrogen energy.

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The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsaem.1c00955.

  • Digital photographs of a series of NIFEX deposited on NF (NF, NIFE0, NIFE25, NIFE50, NIFE75, and NIFE100) (4); SEM and TEM EDX elemental mapping of FeB+S-NIFE25 (4); HRTEM image and SAED pattern of FeB+S-NIFE25 (4); XRD spectrum of FeB+SNIFE25 (5); SEM EDS mappings of a series of NIFEX (NIFE0, NIFE25, NIFE50, NIFE75, and NIFE100) (5); HAADF–STEM with EDX elemental mapping of FeB+S—NIFE25 (5); fitted high-resolution XPS spectra of Fe 2p of FeB+S-NIFE25 and FeB-NIFE25 (7); LSV curves of a series of NIFEX obtained at a scan rate of 5 mV s–1 for FeB-NIFEX and FeB+S-NIFEX (8); Tafel slopes for FeB-NIFEX and FeB+S-NIFEX (8); capacitive current differences at 0.79 V versus RHE against scan rates for FeB–NIFEX and FeB+S–NIFEX (8); double-layer capacitance measurements with scan rates at 2, 4, 6, 8, and 10 mV/s for FeB–NIFEX (8); double-layer capacitance measurements with scan rates at 2, 4, 6, 8, and 10 mV/s for FeB+S–NIFEX (8); Nyquist plots for FeB–NIFEX (inset details of the plots in the high-frequency region) (8); computational MD simulations of a series of NIFEX; snapshots of the OH/NIFEX models in different ratios (A,C) before and (B,D) after the MD simulation was concluded; (9) LSV curves obtained before and after the long-term stability test for FeB–NIFE25 (10); SEM image after long-term stability test for FeB+S–NIFE25 (10); multistep chronopotentiometric curve for FeB+S–NIFE25 (10); amount of theoretically calculated versus actual oxygen production catalyzed by FeB+S–NIFE25 (10); XPS elemental composition analysis of FB+S-NIFEX (5); interaction energies between the NIFEX surface and the OH (9); and comparison of OER performance of FeB+S-NIFE25 with recently reported OER-active transition-metal-based catalysts (8) (PDF)

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