Enhancing activity and stability of bimetallic metal-organic frameworks (MOFs) for overall electrochemical water splitting through nanocomposite formation

Designing efficient, cost-effective, and stable earth-abundant metal electrocatalysts is imperative for the largescale production and commercialization of green hydrogen technologies based on water electrolysis. Multivariate metal-organic frameworks (MOFs), in this regard, have emerged as promising candidates due to their uniform active sites, tuneable structures, and high surface area. However, they typically suffer from low stability under harsh chemical conditions prevalent in alkaline water electrolyzers. Here, we report that combining bimetallic MOFs based on Fe and Ni (FeNi-MOF) with layered double hydroxides (LDHs) not only improves their catalytic activity but also significantly enhances their stability. We propose that synergic interaction between FeNi-MOF and NiMo-LDH tunes the composite's chemical and electronic structure, enhancing water adsorption and dissociation. The optimized nanocomposite showed outstanding electrocatalytic activities for water splitting in 1 M KOH, requiring low overpotentials of 160 mV and 237 mV to attain a 10 mA cm-2 current density for Hydrogen evolution reaction (HER) and Oxygen evolution reaction (OER), respectively. The integrated twoelectrode system utilizing FeNi-MOF@NiMo-LDH bifunctional electrocatalysts required only 1.62 V potential at 10 mA cm-2 with an excellent durability of 50 h. This electrochemical performance surpasses most of the recently reported MOF-based electrocatalysts.