Hollow N-doped carbon nanofiber confined Ru/Ni3Fe@C core-shell heterostructures for boosted alkaline overall water splitting

Ru-decorated graphitic carbon-encapsulated Ni₃Fe particles are embedded in hollow carbon nanofibers as an electrocatalyst. • Graphitic carbon enhances alloy conductivity and hollow porous CNFs facilitate electrolyte penetration and bubble detachment. • Ru nanoparticles reconstruct electronic structure and optimize HER/OER intermediate Gibbs free energies. • The Ru/Ni₃Fe@C/CNF composite accelerates both OER and HER kinetics and achieves outstanding long‑term catalytic stability. Nickel‑iron intermetallic Ni 3 Fe represents a low-cost oxygen evolution reaction (OER) electrocatalyst, yet sluggish hydrogen evolution reaction (HER) kinetics, severe particle aggregation and inferior alkaline stability greatly limit its bifunctional water-splitting application. Hierarchical hollow N-doped carbon nanofiber supported Ru/Ni 3 Fe@C core-shell heterostructures (Ru/Ni 3 Fe@C/CNF) are fabricated via coaxial electrospinning, high-temperature carbonization and liquid-phase Ru reduction. Hollow N-doped carbon nanofibers serve as conductive porous scaffolds, where graphitic carbon shells encapsulate Ni 3 Fe nanoparticles and evenly dispersed Ru nanoparticles form heterointerfaces for electronic regulation. Characterizations confirm carbon-triggered Ni 3 Fe lattice expansion, strong Ru-Ni/Fe charge transfer, and in-situ formation of NiOOH/FeOOH active sites under OER conditions. Electrochemical measurements in 1 M KOH deliver 61 mV HER and 240 mV OER overpotentials at 10 mA cm −2 , outperforming Ni 3 Fe@C/CNF and commercial Pt/C/RuO 2 . Elevated double-layer capacitances (38.9 mF cm −2 for HER, 37.3 mF cm −2 for OER) and lowered charge transfer resistance demonstrate abundant exposed active sites. Benefiting from carbon confinement, 83% and 80% initial activity are maintained after 40 h HER and OER operation, respectively. The symmetric electrolyzer attains a low cell voltage of 1.64 V at 10 mA cm −2 with 92% activity retention over 100 h. Density Functional Theory (DFT) calculations confirm combined carbon encapsulation and Ru decoration upshift Ni 3 Fe d-band center, reduce water dissociation barrier to 0.46 eV and balance H ⁎ /OOH ⁎ adsorption to accelerate catalytic kinetics. This work develops an integrated interface engineering strategy for high-efficiency durable non-noble bifunctional electrocatalysts. The catalyst consists of Ru nanoparticles decorated on graphitic carbon-encapsulated Ni 3 Fe alloy nanoparticles embedded in hollow porous carbon nanofibers (CNFs). Benefiting from its optimized electronic structure, boosted charge transfer capability, and favorable structural stability, the Ru/Ni 3 Fe@C/CNF catalyst demonstrates impressive dual functionality in both OER and HER. Download: Download high-res image (116KB) Download: Download full-size image