Self-standing porous intermetallic Fe3Mn7 phase as bifunctional electrocatalyst towards efficient overall water splitting

Abstract

The urgent need for efficient, stable, and noble-metal-free electrocatalysts for overall water splitting drives the exploration of intermetallic compounds. Herein, a three-dimensional nanoporous electrode D-MnNiFe-30 featuring a bicontinuous poreligament architecture and primarily composed of the Fe3Mn7 intermetallic phase is fabricated via controlled chemical dealloying. This integration of a permeable nanoporous network with a well-defined intermetallic compound facilitates efficient mass/charge transport and stabilizes active sites. The resulting electrode demonstrates outstanding bifunctional activity in alkaline media, with low overpotentials of 32 mV for HER and 329 mV for OER at 10 mA cm-2. When assembled into a symmetric electrolyzer, it achieves 100 mA cm-2 at 1.65 V under industrially relevant conditions and exhibits excellent long-term stability. Density functional theory (DFT) calculations reveal that the pristine Fe3Mn7 surface exhibits strong adsorption of key intermediates, limiting its intrinsic activity. The remarkable experimental performance is therefore attributed to a synergistic enhancement from the defect-rich nanocrystalline nature within the porous framework, which modulates adsorption energetics, coupled with the advantageous mass transport morphology. This work provides a practical dealloying route to high-performance self-supported electrodes and elucidates the critical synergy between defect engineering within an intermetallic phase and a nanoporous architecture for efficient water splitting.