Fig. 5.

Electron density difference plots for MoS₂@Fe-N-C with adsorbed (A) O₂ and (B) OH⁻, respectively. The isosurface value of yellow and cyan regions are 0.003 Bohr⁻³. Yellow contours represent charge accumulations, and cyan contours denote charge depletion. (C) Schematic of O₂ intercalation at the MoS₂/Fe-N-C interface, and the production of OH⁻ during the ORR process as well as its reverse process (OER process). Free energy diagrams of (D) ORR and (E) OER on MoS₂, MoS₂@Fe-N-C surface, and MoS₂@Fe-N-C interface at U = 0 V and U = 1.23 V, respectively.