Fluorine-rich Schiff base ligand derived Fe/N-C-F and Co/N-C-F catalysts for the oxygen reduction reaction: synthesis, experimental validation, and DFT insights

The development of cost effective and durable catalysts for the electrochemical reduction of O 2 to H 2 O is paramount for energy conversion devices such as fuel cells and Zn-air batteries. In this research work, we have developed a unique strategy for the synthesis of active and stable electrocatalysts comprising Fe and Co transition metals in combination with N and F dopants in the carbon matrix. This research also introduces an innovative approach for synthesizing Fe/N-C-F and Co/N-C-F electrocatalysts utilizing organic Schiff base ligands and their coordination complexes with Fe and Co transition metals. The synthesized Fe/N-C-F and Co/N-C-F catalysts have been systematically evaluated for their physicochemical properties and electronic states by using HR-TEM, XPS analysis and electrochemical characterization in 0.1 M aqueous KOH electrolyte. The optimized Fe/N-C-F catalyst shows a half-wave potential of 0.88 V vs. RHE and superior durability evaluated up to 20 000 cycles with only a marginal potential drop of ∼27 mV in its E 1/2 potential value compared to the Pt/C catalyst. Furthermore, the reaction pathway and Gibbs free energy of the ORR intermediates in Fe/N-C-F and Co/N-C-F catalysts have been evaluated by DFT analysis. Featuring a fully optimized Fe/N-C-F catalyst, the full-cell mechanism demonstrates superior activity and stability for the oxygen reduction reaction (ORR).