Electronic Spin Moment As a Catalytic Descriptor for Fe Single-Atom Catalysts Supported on CN.

The electrocatalytic activity of transition-metal-based compounds is strongly related to the spin states. However, the underlying relationship connecting spin to catalytic activity remains unclear. Herein, we carried out density functional theory calculations on oxygen reduction reaction (ORR) catalyzed by Fe single-atom supported on CN (CN-Fe) to shed light on this relationship. It is found that the change of electronic spin moments of Fe and O due to molecular-catalyst adsorption scales with the amount of electron transfer from Fe to O, which promotes the catalytic activity of CN-Fe for driving ORR. The nearly linear relationship between the catalytic activity and spin moment variation suggests electronic spin moment as a promising catalytic descriptor for Fe single-atom based catalysts. Following the revealed relationship, the ORR barrier on CN-Fe was tuned to be as low as 0.10 eV through judicious manipulation of spin states. These findings thus provide important insights into the relationship between catalytic activity and spin, leading to new strategies for designing transition metal single-atom catalysts.