Boosting Electrocatalytic Activity of Single Atom Catalysts Supported on Nitrogen-Doped Carbon through N Coordination Environment Engineering.

ABSTRACT

Nonprecious group metal (NPGM)-based single atom catalysts (SACs) hold a great potential in electrocatalysis and dopant engineering has been extensively exploited to boost their catalytic activity, while the coordination environment of dopant, which also significantly affects the electronic structure of SACs, and consequently their electrocatalytic performance, have been largely ignored. Here, by adopting a precursor modulation strategy, the authors successfully synthesize single cobalt atom catalysts embedded in nitrogen-doped carbon, Co-N/C, with similar overall Co and N concentrations but different N types, that is, pyridinic N (NP ), graphitic N (NG ), and pyrrolic N (NPY ). Co-N/C with the Co-N4 moieties coordinated with NG displays far superior activity for oxygen reduction (ORR) and evolution reactions, and superior activity and stability in both zinc-air batteries and proton exchange membrane fuel cells. Density functional theory calculation indicates that coordinated N species in particular NG functions as electron donors to the Co core of Co-N4 active sites, leading to the downshift of d-band center of Co-N4 and weakening the binding energies of the intermediates on Co-N4 sites, thus, significantly promoting catalytic kinetics and thermodynamics for ORR in a full pH range condition.