Ab initio calculations of high-entropy clusters for oxygen reduction and evolution as well as CO2 reduction reactions

This study introduces a design concept for a high-entropy cluster (HEC) comprising of Fe, Co, Ni, Cu, and Rh metals supported on nitrogen-doped graphene. Five different configurations including CoNiCuRh@FeN4, FeNiCuRh@CoN4, FeCoCuRh@NiN4, FeCoNiRh@CuN4, as well as; FeCoNiCu@RhN4 with the mixing entropy change of Delta Smix = 0.14 meV/K were considered. The positive dissociation potential and negative formation energy suggested the electrochemical and thermodynamic stabilities of these materials. According to density functional theory (DFT + U) calculations, the CoNiCuRh@FeN4 catalyst led to the overpotentials of 0.37 VRHE, 0.37 VRHE, and 0.24 VRHE for the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and CO2 reduction reaction (CO2RR) towards CO production, respectively. It was determined that, FeN4 acted as an active site, while CoNiCuRh-HEC behaved as the modulator. Also, FeNiCuRh@CoN4 catalyst led to the CO2RR overpotential of 0.35 VRHE towards CH3OH formation where CoN4 acted as the active site, and FeNiCuRh-HEC species acted as the modulator surpassing the activity of single-atom catalysts (SAC). Moreover, the density of states (DOS) and charge transfer analyses suggested that, the presence of a high-entropy cluster may enhance the charge transfer and stabilize the reaction intermediates, toward selective methanol formation. Therefore, a DFT-based strategy to design a high-entropy cluster was developed through electrochemistry and beyond.