Spontaneous magnetic field enhancement in nano-frameworks enables efficient ORR

Abstract

The oxygen reduction reaction (ORR) is a pivotal process in sustainable energy conversion and storage devices, such as fuel cells and metal–air batteries. However, its efficiency is severely restricted by sluggish oxygen (O₂) mass transfer. Herein, we report the construction of CoPt₃-based nano-framework catalysts (CoPt₃@NC-NFs) with a unique architecture composed solely of edges and corners. The framework geometry concentrates current density during electrochemical reactions, thereby amplifying the surface magnetic field strength and enhancing the Kelvin force acting on paramagnetic O₂ molecules. This effect actively drives O₂ toward high-field regions on the catalyst surface, enabling directional and accelerated mass transport. The increased Kelvin force promotes the movement of O₂ to high magnetic field regions on the catalysts’ surface, thereby enhancing mass transport of O₂. Consequently, the CoPt₃@NC-NFs exhibit outstanding performance in both the ORR (E_onset = 1.02 V, E_1/2 = 0.89 V, j = −5.8 mA cm⁻² in 0.1 M KOH) and Zn–air batteries (with a power density of 184.8 mW cm⁻² at 305 mA cm⁻²). This work establishes a clear correlation between catalyst microstructure and surface magnetic field, revealing a spontaneous magnetic enhancement mechanism that introduces a new physical perspective for enhancing electrocatalytic activity.