Synergistic Effect of Organic Ligands on Metal Site Spin States in 2D Metal-Organic Frameworks for Enhanced ORR Performance

Two-dimensional metal-organic frameworks (2D MOFs) can serve as effective electrocatalysts for oxygen reduction reaction (ORR) to improve fuel cell technology. However, how to further improve the electrocatalytic performance of 2D MOFs and reveal the mechanism of the ORR remains a great challenge. Hence, density functional theory is used to investigate the influence of organic ligand characteristics on the electrocatalytic ORR activity of 2D MOFs, in which cobalt atoms act as metal nodes. Combined with the calculations of formation energy and dissolution potential, all of the 2D Co-MOFs with different organic ligands show good structural stability. The calculation results showed that cobalt nodes modified by the synergistic regulation of triphenylene and hydroxyl groups exhibit superior electrocatalytic selectivity and activity with a low overpotential of 0.23 V for ORR. Based on the analysis of electronic structure, the enhanced spin state endows the Co node's moderate interaction with the key intermediates, which is conducive to facilitating the ORR process. Therefore, the mechanism of organic ligand regulation to improve the electrocatalytic ORR activity of 2D MOFs is further revealed in this work, which can provide theoretical guidance for the design and development of high-performance electrocatalysts in the future.