Dhakar, ShikhaShikhaDhakarSharma, AnjaliAnjaliSharmaKatiyar, Nirmal KumarNirmal KumarKatiyarParui, ArkoArkoParuiDas, RakeshRakeshDasSingh, Abhishek KumarAbhishek KumarSinghTiwary, Chandra SekharChandra SekharTiwarySharma, SudhanshuSudhanshuSharmaBiswas, KrishanuKrishanuBiswas2025-08-312025-08-312023-10-0110.1016/j.mtener.2023.1013862-s2.0-85171626043http://repository.iitgn.ac.in/handle/IITG2025/26629The nanoengineered high entropy alloy (HEAs) catalysts have attracted the attention of the scientific community due to their exceptional characteristics, wide range of compositional tunability and the utilization of low-cost transition metals. During various electrochemical reactions, the oxidation of carbon-mono-oxide (CO) is an intermediate and it acts as a poison to reduce the efficiency of the reactions. Also, CO is a poisonous gas which is generated during gasoline and diesel combustion in the automobiles. A nanocrystalline HEA catalyst (CoFeNiGaZn) is prepared by easily scalable casting-cum-comminution method, providing pristine catalyst surfaces. It is capable of catalyzing the CO-oxidation to CO<inf>2</inf> with high conversion efficiency (∼98%). Density functional theory calculations show that the high activity of the HEA can be attributed to the presence of a considerable amount of filled states of d<inf>xz</inf> and d<inf>yz</inf> orbital near the Fermi level for Ni atoms over the surface. Due to the favorable transfer of electrons from this orbitals to the lowest unoccupied molecular orbital of O<inf>2</inf> and adsorption of gaseous CO directly on O∗ to form CO<inf>2</inf>, the endothermicity of the rate-determining step is 0.43 eV in the Eley-Rideal pathway.falseCatalyst | Cryomilling | DFT | HEA materials | Low cost | Transition metalsArticle24686069October 202310101386arJournal8WOS:001077651400001