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. 2025 Dec 13;17:757. doi: 10.1038/s41467-025-67439-4

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© The Author(s) 2025

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Fig. 6 — The OER free energy diagrams for NiFeOOH structure with and without O vacancy structure at both a Fe site and b Ni site. c Calculated projected density of states (pDOS) of Fe d band for Fe adsorption site in NiFeOOH and NiFeOOH-V_o structure. d The maximum free energy difference (ΔG_max) under thermodynamic consideration of IrO₂ and NiFeOOH-V_o structure for OER (bule bars), CER (red bars) and hypoCER (orange bars). The e hypoCER and f CER free energy diagrams for NiFeOOH-V_o and IrO₂ structure. g The calculated Pourbaix diagram for chlorine-water system with total chlorine species concentration of 0.5 m (pH > 7.5) based on the corresponding theoretical overpotential of NiFeOOH-V_o and IrO₂ structure. The CHE represents a computational hydrogen electrode⁴⁷. h The charge density difference of Cl adsorbed NiFeOOH-V_o structure and IrO₂, the yellow and blue regions represent electron accumulation and depletion, respectively. i Schematics of promoted OER activity and selectivity over NiFeOOH-V_o structure.