d-Band Center Regulation Facilitated by Asymmetrical Ligand in the Atomically Dispersed Iron Site toward Promoting Oxygen Electrocatalysis Activities

Abstract

The prosperity of aqueous rechargeable Zn–air batteries is hindered by the discontent performance of the oxygen electrocatalyst in the cathode. An important catalyst for oxygen electrocatalyst is an atomically dispersed iron atom embedded in the nitrogen-doped carbon (Fe-NC) material. However, the unsuitable binding energy between the center Fe atom and the reaction intermediate leads to the sluggish oxygen electrocatalyst reaction rate. The regulation of the electron structure of the Fe atom by adjusting the coordinate structure is one effective solution. Here, we prose the substitution of nitrogen atom by sulfur atom, who has weak electronegativity and can donor electron to Fe atom, so the d-band center of Fe atom is elevated. Thus, the Fe-NS active site facilitates the fast *OOH adsorption and the *OH desorption, compared with counterpart Fe-N active site. As a result, the oxygen electrocatalyst reaction kinetics is accelerated. The Fe-NSC catalyst has good compatibility and performance in aqueous rechargeable Zn–air batteries, affording stable charge/discharge process for 1000 h/3000 cycles with a high voltage tolerance (0.74–0.96 V voltage gap) under 10 mA cm^–2. This work brings referential sights to the modification of electron structure of the center atom in the M–N–C-type catalyst.