Magnetic Field Enhanced Oxygen Reduction Reaction via Oxygen Diffusion Speedup

Area of Science:

• Electrochemistry
• Materials Science
• Fluid Dynamics

Background:

• Oxygen mass transfer is crucial for oxygen reduction reaction (ORR) efficiency, particularly at immersed catalyst sites.
• Poor oxygen solubility and slow diffusion in electrolytes limit ORR performance despite interface optimization efforts.

Purpose of the Study:

• To develop a magnetic method for enhancing directional oxygen transport to catalyst sites.
• To overcome mass-transfer limitations in ORR and access previously limited catalytic regions.

Main Methods:

• Demonstration of a magnetic method to induce hydrodynamic pumping of oxygen.
• Application of an external magnetic field (435 mT) to Pt foil electrodes in KOH electrolytes.
• Utilizing residual magnetic fields on magnetic materials (CoPt alloys, Pt/FeCo heterostructures) to enhance surface-magnetohydrodynamic (MHD) effects.

Main Results:

• Achieved a 60% improvement in mass-transfer-limited current densities for Pt foil electrodes.
• Observed synergistic effects from bulk- and surface-MHD flows induced by Lorentz forces.
• Demonstrated permanent ORR enhancement retention using residual magnetic fields on magnetic materials.

Conclusions:

• The magnetic hydrodynamic pumping method effectively boosts oxygen delivery, significantly enhancing ORR performance.
• Magnetohydrodynamics offers a viable strategy to overcome oxygen transport limitations in electrochemical reactions.
• Surface-MHD effects on magnetic materials provide a pathway for sustained ORR enhancement without external fields.