Multifunctional assessment of rock-salt (Co$_{0.2}$Cu$_{0.2}$Mg$_{0.2}$Ni$_{0.2}$Zn$_{0.2}$)O High-Entropy Oxide : CO$_2$ hydrogenation activity and environmental impact

Skalar, Tina (author), Žgajnar Gotvajn, Andreja (author), Legan, Maša (author), Kostinjuk, Andrij Olegovič (author), Likozar, Blaž (author), Tatar, Dalibor (author), Djerdj, Igor (author), Marinšek, Marjan (author)

In this study, high-entropy oxide (HEO) (Co$_{0.2}$Cu$_{0.2}$Mg$_{0.2}$Ni$_{0.2}$Zn$_{0.2}$)O was synthesized via two different approaches, combustion synthesis (CS) and a solvent-deficient mechanochemical method (SDM), and comparatively investigated in terms of structural properties, catalytic performance in CO$_2$ hydrogenation, and environmental impact through phytotoxicity assessment. X-ray diffraction confirmed the formation of a phase-pure cubic rock-salt structure (Fm-3m) for both synthesis routes. However, the CS-derived material exhibited a smaller crystallite size, a higher lattice microstrain, and more pronounced structural anisotropy compared to the SDM counterpart, while both materials showed relatively low specific surface areas. Catalytic testing was performed for CO$_2$ hydrogenation at 20 bar, H$_2$/CO$_2$ = 3, and 200°C–300°C. Both HEO catalysts showed high selectivity toward methanol. The CS catalyst demonstrated markedly superior performance, achieving up to ∼16 mol% CO$_2$ conversion and significantly higher methanol space-time yield (4.2 mmol gcat$^{−1}$ h$^{−1}$) at 300°C compared to the SDM sample. The enhanced activity is attributed to a higher defect density and lattice distortion induced by the combustion route. Environmental assessment using Lemna minor revealed that metal leaching from the HEOs significantly affected phytotoxicity. The CS-derived material showed higher leaching of Cu, Co, and Ni, highlighting a trade-off between catalytic activity and environmental stability.

• Language: English
• Keywords: carbon dioxide utilization, high-entropy oxides, methanol, phytotoxicity
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Publication status: Published
• Publication version: Version of Record
• Year: 2026
• Number of pages: 15 str.
• Numbering: Vol. 18, iss. 19, art. e71097
• PID: 20.500.12556/RUL-189581
• UDC: 620.1:504.5
• ISSN on article: 1867-3880
• DOI: 10.1002/cctc.71097
• COBISS.SI-ID: 294376707
• Publication date in RUL: 09.10.2026

Record is a part of a journal

• Title: ChemCatChem
• Shortened title: ChemCatChem
• Publisher: Wiley-VCH
• ISSN: 1867-3880
• COBISS.SI-ID: 33675013

Licences

• License: CC BY-NC-ND 4.0, Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
• Link: http://creativecommons.org/licenses/by-nc-nd/4.0/
• Description: The most restrictive Creative Commons license. This only allows people to download and share the work for no commercial gain and for no other purposes.

Secondary language

• Language: Slovenian
• Keywords: izraba ogljikovega dioksida, oksidi z visoko entropijo, metanol, fitotoksičnost