Axial ligand engineering enhanced CoN4-based catalysts as efficient electrocatalysts for ORR/OER with low overpotentials: A DFT study

Bifunctional electrocatalysts are key for achieving efficient energy conversion in Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER), essential processes in renewable energy applications. Despite their critical role, achieving optimal activity and stability in these catalysts remains a formidable challenge, hindering the full realization of sustainable energy systems. Within the confines of this study, the catalytic efficiencies pertaining to ORR/OER of 22 distinct CoN4C-X catalysts, encompassing both unadulterated CoN4C and those axially coordinated, were meticulously evaluated employing density functional theory (DFT). The outcomes of our investigation reveal that CoN4C-O emerges as a promising bifunctional catalyst, characterized by its notably low overpotential (0.36 V/0.34 V). Furthermore, a linear relationship involving the d-band center, ICOHP, and adsorbed intermediates was elucidated, substantiating their efficacy as accurate descriptors of catalytic performance. Subsequent analysis of electronic structural properties unveiled the manifestation of pronounced peaks at the Fermi energy level, indicative of a robust interaction between Co 3d orbitals and N 2p orbitals with the oxygen ligand, substantially enhancing the catalyst's activity. This body of research contributes significantly to the deepened comprehension of five-coordinated CoN4C catalysts and furnishes a robust theoretical foundation for the methodical design of high-efficiency electrocatalysts utilizing Co-based carbon materials.