Sun, S., Zhou, J., Xi, S., Tan, H. R., Wei, F., Seng, D. H. L., Lieu, W. Y., Ren, Y., Wang, S., & Seh, Z. W. (2024). Short-range disorder mediated stability of Zn in rock-salt MgO beyond configurational entropy. Journal of Materials Chemistry A, 12(31), 20064–20076. https://doi.org/10.1039/d4ta02175d
Abstract:
High-entropy rock-salt Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O has been intensively studied in the energy field due to
its unique composition–function relationship and synergistic effect. Entropy-stabilization of Cu and Zn in
rock-salt Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O is the key characteristic of this material. As a parent binary oxide,
ZnO exists as wurtzite in nature. Herein, for the first time we investigated the role of late 3d transition
metals Co, Ni and Cu in stabilizing Zn in MgO-based rock-salt oxides under the same configurational
entropy condition and their structural stability in alkaline solutions. We found that Co, Ni and Cu can
increase the Zn solubility in MgO-based rock-salt oxides, Mg0.50TM0.25Zn0.25O (TM = Co, Ni and Cu,
configurational entropy 1.04 R), with Cu being the best. Simulation results show that the formation
energy of Zn substitution for Mg is the lowest in Mg0.50Cu0.25Zn0.25O. Moreover, Cu incorporation can
create a wide metal–oxygen bond length distribution, which causes short-range disorder and enhances
Zn stabilization. Surprisingly, CuO with square-planar Cu–O coordination is more effective in stabilizing
rock-salt ZnO in MgO, compared to rock-salt CoO and NiO, as Cu2+ ions undergo splitting of eg orbitals
due to strong Jahn–Teller distortion. Mg0.50Cu0.25Zn0.25O with medium entropy 1.04 R can stabilize 25
at% Cu and 25 at% Zn simultaneously. Besides, the Ni substitution is found to be effective in improving
the structural stability in alkaline solutions. This work gives insight into understanding the
complementation of orbital distribution in high-entropy oxides for metal stabilization, and provides
a rational composition design for applications in the energy field.
License type:
Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Funding Info:
This research is supported by core funding from: Agency for Science, Technology and Research
Grant Reference no. : Central Research Fund Award