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

Abstract

The development of cost effective and durable catalysts for the electrochemical reduction of O₂ to H₂O 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.