Structural Reconstruction and Electronic Microenvironment of Active FeCoNiOOH Support Optimized by Single Mo Atoms...

To figure out the function of single atoms in modulating electro-active support, the fundamental study on how single atoms manage reconstruction dynamics and optimize the electronic structure of the support is imperative to provide advanced cognition of activity origin for decent OER kinetics. With FeCoNi(OH)_x and Mo-ensemble FeCoNi(OH)_x as the proof-of-concept precatalysts, we demonstrate the defects created by molybdate dissolution-redeposition dynamic equilibrium (Mo ensemble atomization), ready for favorite hydroxide adsorption triggers self-adaptive structure reconstruction, and electronic metal support interaction (EMSI) improves bonding covalency of the edge-shared octahedral Co⁴⁺/Ni⁴⁺ dual-site motifs for direct intramolecular O_lattice-O_lattice radical coupling. Orchestrated with pH-dependent CV experiments and ¹⁸O-labelled catalyst coupled with in situ GC-MS measurements, O K-edge, Mo/Fe/Co/Ni K-edge/L-edge XAS, and KPFM combined with XPS valence band analyses unravel that atomization and EMSI effects work together to in situ optimize electronic microenvironment to initiate ligand (O 2p π_nb band) to metal (d band) charge transfer, actualizing the oxygen hole with radical character in O 2p π_nb band and realizing highly catalytic stability of LOM-active FeCoNiOOH support. Accordingly, the SA-Mo-FeCoNiOOH catalyst affords 500 mA/cm² at an overpotential of 394 mV and exhibits high stability at 1000 mA/cm² over 100 days with a potential decay rate as 40.8 µV/h.