Co-Doped Nanoporous Fe₃P Self-Supported Electrodes for Enhanced Alkaline Hydrogen Evolution

Transition-metal phosphides are promising non-noble-metal electrocatalysts for alkaline hydrogen evolution, yet further improving their performance remains challenging. In this work, a Co-doped nanoporous Fe₃P self-supported electrode was fabricated by vacuum high-frequency induction and melt spinning of Fe₇₅Co₅P₂₀ precursor alloys, followed by electrochemical dealloying. Nanoporous Fe₃P prepared from Fe₈₀P₂₀ was used as the reference. Structural analyses show that dealloying selectively removes the α-Fe phase while preserving the Fe₃P framework, resulting in a three-dimensional nanoporous architecture. XPS results further confirm successful Co incorporation and reveal that Co doping modifies the local chemical environment of Fe and P. Benefiting from the combined effects of Co incorporation and the nanoporous structure, np-Co-Fe₃P exhibits significantly improved HER performance in 1.0 M KOH, requiring only 70 mV to reach 10 mA cm^-2, much lower than that of np-Fe₃P (199 mV). In addition, np-Co-Fe₃P shows a smaller Tafel slope of 94 mV dec^-1, lower charge-transfer resistance, and a larger double-layer capacitance of 109.4 mF cm^-2. This work demonstrates an effective strategy for enhancing the alkaline HER performance of Fe-based phosphides through the combination of Co incorporation and dealloying-derived nanoporous architecture.