Utilization of structural high entropy alloy for CO oxidation to CO2

Abstract

The 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 CO2 with high conversion efficiency (~98%). DFT calculations show that the high activity of the HEA can be attributed to the presence of a considerable amount of filled states of dxz and dyz orbital near the Fermi level for Ni atoms over the surface. Due to the favourable transfer of electrons from this orbitals to the LUMO of O2 and adsorption of gaseous CO directly on O* to form CO2, the endothermicity of the rate-determining step is 0.43 eV in the Eley-Rideal pathway.