Tip-Enhanced Oxygen Reduction on Pt@Ni Cones via Concentrated Electric and Magnetic Fields

Efficient oxygen reduction reaction (ORR) is crucial for energy conversion technologies, yet its sluggish kinetics remain a significant challenge. Beyond optimizing the catalyst's intrinsic properties, field effects can also profoundly impact the microenvironment at the catalyst/electrolyte interface, thereby affecting electrocatalytic performance. This study explores the tip-enhanced ORR by leveraging the coupled effects of electric and magnetic fields at the reaction interface. The Pt-loaded ferromagnetic Ni cone electrode generates strong localized electric fields that reorganize interfacial water molecules into a more ordered structure. This strengthens hydrogen bonding between the electrolyte and reaction intermediates, which in turn facilitates proton-coupled electron transfer and accelerates the rate-limiting *OH desorption into interfacial water matrix. Additionally, the amplified electric fields at tips accelerate OH^- electromigration away from the catalyst surface, while the migration current couples with the concentrated magnetic fields near tips to drive strong magnetohydrodynamic flows. These intensified flows effectively enhance O₂ molecule delivery to wider electrode surface and facilitate better OH^- product removal, thus improving the overall reaction efficiency. This strategy of concentrating both E/M fields using the field-effect catalyst optimizes the ORR kinetics at the interface as well as the mass transport dynamics near interface, offering an effective approach for advancing ORR performance.