Self-Standing NiFe MOF@Ni₃S₂ Core-Shell Hierarchical Heterostructure for Enhanced Oxygen Evolution Activity

Metal-organic frameworks (MOFs) have received widespread attention in various energy related applications due to their unique structural characteristics. Nevertheless, the inherent low electronic conductivity of MOFs is a major limitation for their competitive activity. Herein, we synthesized a self-standing NiFe MOF@Ni₃S₂ core-shell hierarchical heterostructure through using Ni₃S₂ grown on nickel foam (NF) as a semisacrificial template, in which the highly conductive Ni₃S₂ nanosheets core endows the hybrid with rapid charge transfer capability, and the bimetallic NiFe MOF nanosheets provide abundant exposed active sites. Benefiting from the structural and compositional advantages, the enhanced electrocatalytic activity of the as-obtained NiFe MOF@Ni₃S₂/NF has been achieved toward alkaline oxygen evolution reaction (OER). As a result, the NiFe MOF@Ni₃S₂/NF only requires overpotentials of 177 and 219 mV to yield OER current densities of 10 and 100 mA cm^-2, respectively, and exhibits a very small Tafel slope of 24.1 mV dec^-1 and high durability, making it among the most efficient earth-abundant OER catalysts. This study will inspire further construction of MOF-based nanocomposites for applications in electrochemical renewable energy systems.