Exploring the effect of graphite-coating on hexanary high entropy metal oxides towards efficient water electrocatalysis

  • Shakeel Abbas orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Akbar Hussain orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Muhammad Asim orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Tehmeena Maryum Butt orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Banafsha Habib Ur Rehman orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Javeria Arshad orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Amina Hana orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Sadia Kanwal orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
  • Muhammad Yasir orcid

    Department of Material Science and Engineering, Institute of Space Technology, Islamabad 44000, Pakistan
  • Naveed Kausar Janjua orcid

    Department of Chemistry, Quaid-i-Azam University, Islamabad 45320, Pakistan
Article ID: 3955
DOI: https://doi.org/10.59400/mtr3955
Keywords: water electrocatalysis, high entropy oxides, graphite coating, low charge transfer resistances, robust kinetics

Abstract

High-entropy oxides (HEOs) have emerged as promising electrocatalysts due to their high configurational entropy, modular electronic structures, and defect-rich multicationic lattices. However, modifying their electrochemical kinetics through conductive surface modification remains completely unknown. An Al-rich hexanary spinel, Cr, Cd, Fe, Mg, and Mn-based materials were synthesized using a sol-gel method and then modified with graphite (5–20 wt%) via rotary ball milling to improve conductivity and interfacial charge transfer, resulting in a stable spinel phase as validated by Rietveld-refined XRD. The addition of graphite significantly increased anodic activity, with the 10 wt% composite (HEO-10C) achieving a peak current density of 47.09 mA cm−2 in 1 M KOH + methanol. This was followed by decreased charge-transfer resistance and better electron-transfer kinetics. The graphite-HEO interface allows for faster reaction pathways, as evidenced by a high diffusion coefficient (8.65 × 10−8 cm2 s−1), a heterogeneous electron-transfer rate constant (3.75 × 10−4 cm s−1), and a low Tafel slope of 97 mV dec−1. To better measure intrinsic activity, we add a new descriptor, Jη = (Jₚ (peak current density)−Jₒₙₛₑₜ (onset current density)), which represents the net operating current above onset. Jη correlates strongly with traditional kinetic measurements, highlighting the conductivity-driven performance gain in HEO-10C (44.59 mA cm−2), which is about 1.6× greater than the uncoated HEO. These findings confirm graphite coating as a viable method for modifying multication HEO electrodynamics and introduce a new measure for assessing advanced oxide-based electrocatalysts.

Published
2026-03-06
How to Cite
Abbas, S., Hussain, A., Asim, M., Maryum Butt, T., Habib Ur Rehman, B., Arshad, J., Hana, A., Kanwal, S., Yasir, M., & Kausar Janjua, N. (2026). Exploring the effect of graphite-coating on hexanary high entropy metal oxides towards efficient water electrocatalysis. Materials Technology Reports, 4(1). https://doi.org/10.59400/mtr3955
Issue
Vol. 4 No. 1 (2026)
Section
Article

Copyright (c) 2026 Shakeel Abbas, Akbar Hussain, Muhammad Asim, Tehmeena Maryum Butt, Banafsha Habib Ur Rehman, Javeria Arshad, Amina Hana, Sadia Kanwal, Muhammad Yasir, Naveed Kausar Janjua

Creative Commons License

This work is licensed under a Creative Commons Attribution 4.0 International License.

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