Study of oxygen reduction reaction on binuclear-phthalocyanine with Fe-Fe, Co-Co, and Fe-Co dual-atom-active sites using density functional theory

Although the N4-macrocyclic ligands have been used to develop single-atom catalysts (SACs), their utilization for the construction of dual-atom catalysts (DACs) for electrocatalytic oxygen reduction reaction (ORR) is poorly investigated. Herein, a binuclear phthalocyanine (bN-Pc) was explored as a theoretical model for the construction of FeFe-bN-Pc, CoCo-bN-Pc, and FeCo-bN-Pc dual-atom-site configurations and their ORR activity along with mechanisms were investigated systematically in alkaline media, using density functional theory (DFT) calculations. The results indicated that the dual-atom-bN-Pc models, having close proximity between adjacent metals, invited individual O-atom of O2 for coordination on both sites, forming a cis-bridged-O2 adduct. The Gibbs free energy studies showed that the decomposition of O2 on dual-atom sites was the rate-determining step, and the Fe-Co-bN-Pc had a lower energy barrier (0.591 eV) for this step as compared to Fe-Fe-bN-Pc (0.641 eV) and Co-Co-bN-Pc (0.692 eV), which justifies its stronger ORR performance. The synergistic effect of Fe-Co collaboration, the close proximity of Fe-Co, and the significant e- donation from the 3d-orbital of active sites into the *orbital of O2 can be attributed to this decrease in limiting the potential for the rate-determining step on Fe-Co-bN-Pc. For future ORR electrocatalysts, this work offers a scientific and engineering perspective on the construction of dual-atom active sites employing molecular moieties. (c) 2023 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.

Automated summary

In this study, density functional theory calculations were used to investigate the activity and mechanism of binuclear phthalocyanine (bN-Pc) models combined with Fe and Co for the oxygen reduction reaction (ORR) in alkaline media. The results showed that Fe-Co-bN-Pc exhibited stronger ORR performance with a lower energy barrier. This research provides a scientific and engineering perspective for the construction of dual-atom active sites in future ORR electrocatalysts.