Facile synthesis multifaceted Fe₃O₄ based on N-Doped Porous Carbon frameworks for ORR / OER and study of an external magnetic field

Global efforts increasingly focus on developing advanced non-noble metal electrocatalysts for efficient Oxygen Reduction Reaction (ORR) and Oxygen Evolution Reaction (OER), crucial for energy conversion technologies. To address this, we synthesized a novel bifunctional electrocatalyst, Fe3O4 on nitrogen-doped carbon foam (Fe3O4/N-CF) via a very easy single-step pyrolysis of urea, glucose, and a ferric salt in NaCl salt as a template. The multifaceted Fe3O4 nanocrystals were thoroughly characterized by X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDS), and Transmission Electron Microscopy (TEM). This bifunctional Fe3O4/N-CF was evaluated for ORR and OER in alkaline media within a magneto-electrochemical system. The application of a magnetic field significantly enhanced the ORR performance, leading to a remarkable similar to 50 % increase in current density. This enhancement is not solely due to the well-known magnetohydrodynamic (MHD) effect on mass transport. We observed a crucial kinetic influence, as evidenced by a reduction in the Tafel slope from -75.5 to -68 mV/dec and a positive shift in both the onset and half-wave potentials. This kinetic effect was prominent on the Fe3O4/N-CF catalyst, whereas the magnetic field only influenced the diffusion-limited current on the bare N-CF. For OER, the current density for Fe3O4/N-CF sharply increased (five-fold at 400 mT), while remaining unaffected on bare N-CF. The Fe3O4/N-CF exhibited a minimal bifunctional potential difference (Delta E) of 700 mV at 400 mT, comparable to benchmark catalysts (Pt/C for ORR and IrO2 for OER, combined: 680 mV). These findings demonstrate a unique synergistic contribution from both paramagnetic O-2 molecules and the magnetic Fe3O4 electrocatalyst, highlighting the potential for magnetic fields to not only enhance mass transport but also to modulate reaction kinetics for improved electrocatalytic performance in practical applications.

Journal

ELECTROCHIMICA ACTA

Year

2025

Volume

541

ISSN

0013-4686

eISSN

1873-3859

DOI

10.1016/j.electacta.2025.147319

WoS UID

WOS:001583839200004