High entropy oxide

High entropy oxides (HEOs) are complex oxides that contain five or more different metal cations in the same amount and have a single-phase crystal structure. The first HEO with formula Cu0.2Co0.2Mg0.2Ni0.2Zn0.2O, and having the rock salt structure, was reported in 2015 by Rost et al.[1] Notably, not all of the parent compounds are stable in the rock salt structure at ambient pressure and room temperature: CuO has a monoclinic structure and ZnO is usually stable in the wurtzite structure. The possibility of stabilizing all these binary compounds into a single rock salt phase is a direct effect of the value of the configurational entropy, exceptionally large in case of a multicomponent (generally up to 5 components) mixture, which compensates for the unfavourable correspondent enthalpic contribution.

Properties

High entropy oxides offer a new paradigm in material science, leading to the synthesis and design of innovative oxides materials with new physical and structural properties. Cu0.2Co0.2Mg0.2Ni0.2Zn0.2O ha been investigated as a promising material for applications in energy production and storage, e.g. as anode material in Li-ion batteries,[2] or as large k dielectric material,[3] or in catalysis.[4][5]

References
  1. Rost, Christina M.; Sachet, Edward; Borman, Trent; Moballegh, Ali; Dickey, Elizabeth C.; Huo, Dong; Jones, Jacob L.; Curtarolo, Stefano; Maria, John-Paul (2015). "Entropy-stabilized oxides". Nature Communications. 6: 8485. Bibcode:2015NatCo...6.8485R. doi:10.1038/ncomms9485. PMC 4598836. PMID 26415623.
  2. Sarkar, Abhishek; Velasco, Leonardo; Wang, Di; Wang, Quingsong; Talasila, Gopichand; de Biasi, Lea; Kübel, Christian; Brezeniski, Torsten; Battacharya, Subramshu S.; Hanh, Horst; Breitung, Ben (2018). "High entropy oxides for reversible energy storage". Nature Communications. 9 (1): 3400. Bibcode:2018NatCo...9.3400S. doi:10.1038/s41467-018-05774-5. PMC 6109100. PMID 30143625.
  3. Béradan, David; Franger, Sylvain; Dragoe, Diana; Meena, Arun Kuman; Dragoe, Nita (2016). "Colossal dielectric constant in high entropy oxides". Physica Status Solidi Rapid Resarch Letter. 10 (4): 328–333. arXiv:1602.07842. Bibcode:2016PSSRR..10..328B. doi:10.1002/pssr.201600043. S2CID 101808600.
  4. Chen, Hao; Zhang, Pengfei; Peng, Honggeng; Abney, Carter W.; Jie, Kecheng; Liu, Xiaoming; Chi, Miaofang; Dai, Sheng (2018). "Entropy-stabilized metal oxide solid solutions as CO oxidation catalysts with high-temperature stability". Journal of Materials Chemistry A. 6 (24): 11129. doi:10.1039/c8ta01772g.
  5. Fracchia, Martina; Ghigna, Paolo; Pozzi, Tommaso; Anselmi Tamburini, Umberto; Colombo, Valentina; Braglia, Luca; Torelli, Piero (2020). "Stabilization by Configurational Entropy of the Cu(II) Active Site during CO Oxidation on Mg0.2Co0.2Ni0.2Cu0.2Zn0.2O". Journal of Physical Chemistry Letters. 11 (9): 3589–3593. doi:10.1021/acs.jpclett.0c00602. PMID 32309955.
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