Interfacial Electronic Coupling and Surface Reconstruction in Co(OH)₂@NiFe-btz for Durable Alkaline Oxygen Evolution

Coupling metal hydroxides with coordination frameworks offers a route to active and durable oxygen evolution reaction (OER) electrodes. A binder-free Co(OH)₂@NiFe-btz heterostructure, where btz is 1,4-bis(4H-1,2,4-triazol-4-yl)benzene, is constructed on nickel foam through solvothermal growth followed by electrodeposition. Microscopy reveals close contact between Co(OH)₂ nanosheets and the framework. Ultraviolet and x-ray photoelectron spectroscopy indicate interfacial charge redistribution consistent with the work-function difference, while electron paramagnetic resonance detects paramagnetic states. In 1.0 M KOH, the electrode delivers 10 mA cm^-2 at an overpotential of 219 mV, exhibits a Tafel slope of 57.1 mV dec^-1, and operates at 100 mA cm^-2 for 1000 h. Operando Raman spectroscopy reveals potential-dependent formation of a cobalt/nickel oxyhydroxide-like surface phase. Isotope-labeling mass spectrometry and infrared spectroscopy of the target electrode, considered alongside electrochemical probes, are consistent with possible lattice-oxygen participation, without establishing its fraction of the oxygen-evolution flux. Density functional theory calculations on idealized precursor structures show that interfacial coupling and an imposed oxygen vacancy modify metal d and O 2p states and reduce the largest uphill free-energy step in a candidate lattice-oxygen pathway. Together, these results connect framework-hydroxide coupling with enhanced electrode performance and the evolution of its catalytic surface.