Electronic structure engineering of Fe-NC catalysts by proximity electronic effect of S ligand for enhanced oxygen electrocatalysis

Abstract Achieving precise control over electronic modulation has always been challenging in the strategy of modifying transition metal-nitrogen/carbon (M-NC) with heteroatoms for oxygen reduction and evolution reaction (ORR/OER). In this study, we propose a novel precursor coordination strategy that successfully achieves accurate control over the particle size of Fe metal and the micro-distance between S and Fe species through differentiated precursor coordination effects, thereby enabling direct electronic modulation and remote electronic modulation of Fe species. For the two distinct modes of electronic modulation, the direct electronically modulated Fe/S L NC exhibits exceptional ORR activity (E 1/2 = 0.89 V) and an oxygen overpotential difference between ORR and OER (ΔE = 0.70 V), rendering it highly promising for applications in rechargeable zinc-air batteries. Density functional theory (DFT) theoretical calculations demonstrate that direct electron modulation significantly reduces energy barriers for ORR/OER and effectively enhances reaction rates. Analysis based on d-band center theory reveals that direct electron modulation lowers the d-band center position on active sites of Fe and promotes desorption processes of oxygen-containing intermediates. These findings provide valuable insights for future doping strategies aimed at modulating metal active sites using heteroatoms. Graphical Abstract The present study proposes an innovative precursor coordination strategy for precise control of the micro-distance between S atoms and Fe active sites, thereby achieving accurate regulation of two distinct modes of electronic modulation exerted by S atoms on Fe active sites. The direct electronically modulated Fe/S L NC demonstrates exceptional ORR activity (E 1/2 = 0.89 V) and a minimal oxygen overpotential (0.70 V), superior to the values for remotely electronically modulated Fe/S T NC.