Ru-doped CoFe MOF-derived Co3O4-Fe2O3 heterostructure via mild pyrolysis for efficient oxygen evolution

A Ru-doped CoFe MOF-derived Co 3 O 4 -Fe 2 O 3 heterostructure was fabricated via mild pyrolysis. • The low-temperature strategy preserves the 2D MOF nanosheet scaffold. • Ru incorporation modulates Co/Fe electronic states and suppresses structural aggregation during mild pyrolysis. • Ru 0.024 CoFe MOF-250 requires only 227 mV at 20 mA cm −2 with a Tafel slope of 33.67 mV dec −1 . • Excellent durability is demonstrated by only 8.3 mV potential increase after 100 h at 20 mA cm −2 . Metal-organic frameworks (MOFs) are promising for the oxygen evolution reaction (OER), yet they suffer from framework collapse and active-site aggregation during high-temperature pyrolysis. Herein, a Ru-doped CoFe MOF is grown in situ on nickel foam (NF) and subsequently annealed at 250 °C, forming a Co 3 O 4 -Fe 2 O 3 @Ru 0.024 CoFe MOF heterostructure. The incorporation of Ru modulates the local electronic structure of the Co/Fe centers, while mild annealing at 250 °C generates Co 3 O 4 -Fe 2 O 3 nanophases within the partially preserved MOF nanosheet scaffold. This creates intimate heterointerfaces that facilitate rapid charge transfer. In 1.0 M KOH, the optimized electrode delivers a current density of 20 mA cm -2 at an overpotential of only 227 mV, exhibits a low Tafel slope of 33.67 mV dec −1 , and achieves an electrochemical surface area (ECSA) of 133.5 cm 2 . After 100 h of operation at 20 mA cm −2 , the potential increases by merely 8.3 mV. This work presents an effective strategy that combines Ru doping with mild pyrolysis to construct efficient and stable MOF-based OER electrocatalysts.