Fe-embedded graphitic carbon nanofibers for efficient urea electrooxidation and stable oxygen reduction reaction in acidic media

Fe nanoparticle-incorporated carbon nanofibers (Fe-CNFs) were successfully synthesized via electrospinning of a ferrous acetate/PVA solution followed by vacuum drying and calcination at 850 degrees C. SEM and TEM analyses confirmed the formation of uniform nanofibers containing well-dispersed metallic Fe nanoparticles encapsulated within partially graphitized carbon layers. XRD revealed the presence of crystalline alpha-Fe together with minor Fe2O3 and graphite reflections. Magnetic measurements demonstrated ferromagnetic behavior at both 5 K and 300 K with a clear divergence between ZFC and FC curves, confirming the presence of multi-domain Fe nanoparticles embedded in the carbon matrix. Electrochemically, the Fe-CNFs showed pronounced activation behavior in 1.0 M KOH, where strong Fe(ii)/Fe(iii) redox peaks in the first cycle diminished upon cycling due to surface reconstruction and the formation of Fe-oxyhydroxide species. Activated fibers exhibited excellent catalytic activity toward urea oxidation, achieving current densities above 120 mA cm-2 in 2.0 M urea at 50 mV s-1 and demonstrating a negative shift in onset potential with increasing urea concentration. In acidic medium (0.5 M H2SO4), the fibers displayed stable capacitive behavior with suppressed Fe redox activity. Remarkably, the Fe-CNFs exhibited strong oxygen reduction reaction activity in acid along with exceptional durability. Additionally, electrospinning directly onto a silicon wafer produced a compact Fe-CNF film (approximate to 7.5 & micro;m thick) strongly fused to the substrate, forming a conductive and mechanically stable coating suitable for integrated electrochemical devices Overall, the results demonstrate that the introduced Fe-CNFs combine robust structural stability, magnetic functionality, and versatile electrocatalytic performance, highlighting their potential as low-cost catalysts for different applications.

Journal

MATERIALS ADVANCES

Year

2026

Volume

7

Issue

5

Pages

2991-3003

eISSN

2633-5409

DOI

10.1039/d5ma01440a

WoS UID

WOS:001690811000001