Manipulating the spin state to activate the atomically dispersed Fe–N–C catalyst for oxygen reduction

Magnetic moment of 3d xz + 3d yz is a good ORR activity descriptor for Fe–N–C with e1g. Medium spin Fe( iii ) after NC–N doping balances O 2 activation and *OH desorption by tuning hybridization degree between Fe 3d xz ( yz ) and ORR intermediates π* orbitals.