Interfacial coupling-driven catalytic enhancement in self-supported NiMnCr LDH coupled with bimetallic NiMn MOF nanoarchitectures for energy-efficient overall water splitting and urea oxidation

Efficient electrochemical water splitting hinges on the development of robust catalysts that enhance both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) kinetics. In this work, a series of bimetallic NiMn-based bimetallic metal-organic frameworks (MOFs) integrated with NiMnCr LDH were synthesized, with precise control over chromium content. The NiMn MOF/NiMnCr LDH_0.005 (NM MOF/NMC LDH_0.005) composite demonstrated superior bifunctional electrocatalytic activity toward HER, OER, and urea oxidation reaction (UOR) with low overpotentials and favorable Tafel slopes. The NM MOF/NMC LDH_0.005 electrocatalyst exhibits the best electrocatalytic activity with very low overpotentials of 370.3 mV for OER (at 100 mA cm−2 current density), 215.9 mV for HER (at 10 mA cm−2 current density), and 1.42 V for UOR (at 100 mA cm−2 current density). This catalyst exhibited outstanding charge transfer kinetics, large electrochemically active surface area, and remarkable stability over prolonged operation. The NM MOF/NMC LDH_0.005 hybrid also enabled energy-efficient hydrogen production in a two-electrode urea electrolyzer configuration by achieving a cell potential corresponding to E₁₀ = 1.65 V, highlighting its practical applicability. Detailed structural, spectroscopic, and electrochemical analyses reveal that synergistic interfacial interactions, optimized electronic structures, and hierarchical nanostructures drive the exceptional catalytic performance.