Fig. 1: Conceptual design and microstructural characterisation of the as-prepared FePMoG and Fe/SAs@Mo-based-HNSs eletrocatalyst.

a General characteristics comparison of the common substrate precursors for SACs (more details presented in Table S1); b schematic of synthesis of the Fe/SAs@Mo-based-HNSs eletrocatalyst; c SEM image, d TEM image, with inset of the SAED pattern, e high-resolution TEM image, and f STEM image of an FePMoG with an Fe3+: PMo molar ratio of 25:1, and the corresponding EDS elemental mapping of Fe (green), Mo (violet), phosphorus (P; orange), and oxygen (O; cyan).