Harnessing Bio-Inspired Axial Coordination to Boost Synergistic Effects for Enhanced Bifunctional Oxygen Electrocatalysis

Abstract

Strategic alteration of the chelating atoms around the metal center can modify the electronic band structure of the electrocatalyst, improving its performance in oxygen evolution and reduction reactions (OER/ORR). Advancements in the development of catalysts with heteroatoms and axial modifications in the coordination sphere are mostly limited to single-molecule electrocatalysts or elevated temperature-mediated pyrolysis approaches for oxygen electrocatalysis. Inspired by biological catalytic systems with axial coordination, a pyrolysis-free strategic methodology is adopted for the synthesis of an iron-metaled covalent organic polymer matrix axially laminated over cobalt-based metal-organic framework through an imidazole moiety. Precise engineering of coordination atoms in synthesized core-shell material, featuring dual metal sites with distinct neighboring atom exhibits mutual synergy due to the presence of bridging imidazole moiety between two metal sites. Modulated synergism navigates the electronic structure such that it favors specific reactant adsorption on specific metal sites during bifunctional O₂ electrocatalysis as confirmed through in situ Raman spectroscopy and in situ attenuated total reflection infrared (ATR-IR) spectroscopy. Through dynamic correlation between the in-situ studies and modified d-band center obtained theoretically, the pivotal role of axial coordination linkage mediated synergism favoring ORR/OER process via target-specific reactant adsorption is demonstrated.