Functional Engineering Iron Single-Atom Sites on MOF Supports for Enhanced Electrochemical Water Splitting.

The precise control of the local environment, electronic configuration, and electrocatalytic performance of transition metal single-atom sites on nitrogen-carbon supports (M-N-C) is essential for electrolytic hydrogen production due to the inherent rigidity of the catalytic active centers. A highly catalytically active and durable bifunctional metal single-atom site on nitrogen-carbon supports (M-N─C; M═Fe, Co, and Cu) is demonstrated using a porphyrin-based metal-organic framework (MOF) strategy. Engineered iron single-atom sites on nitrogen-carbon support (Fe-N─C) demonstrate remarkable electrocatalytic performance for both the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in an alkaline electrolyte. This is achieved through the optimization of the coordination structure and a large volume of active sites, which advance the intrinsic catalytic activity. The Fe-N─C catalyst exhibits low overpotentials of ≈288.0 mV for the OER and 206.0 mV for the HER at roughly ≈10 mA cm in 1.0 m KOH. This improved catalytic performance is due to enhanced Fe─N─C coordination, which promotes the formation and activation of the vital O═Fe═O intermediate. This, in turn, improves the electrocatalytic properties by reducing the energy barriers of the intermediates and products involved. This strategy demonstrates the enrichment of the micro-environment Fe-N with tunable flexibility, aiding in the rational design of durable electrocatalysts at the atomic scale.