In situ growth of highly active Cu–Fe spinel materials on N-doped porous carbon spheres via an adjustable localized microenvironment

Cu 0.86 Fe 2.14 O 4 spinel grown in situ on N-doped porous carbon spheres has favorable oxygen reduction property, and the excellent stability of the Cu 0.86 Fe 2.14 O 4 spinel structure provides the overall material with stability over a long period of time.