Atomic-Level Modulation of Electronic Density at Cobalt Single-Atom Sites Derived from Metal–Organic Frameworks: Enhanced Oxygen Reduction Performance

Demonstrated here is the correlation between atomic configuration induced electronic density of single-atom Co active sites and oxygen reduction reaction (ORR) performance by combining density-functional theory (DFT) calculations and electrochemical analysis. Guided by DFT calculations, a MOF-derived Co single-atom catalyst with the optimal Co₁-N₃PS active moiety incorporated in a hollow carbon polyhedron (Co₁-N₃PS/HC) was designed and synthesized. Co₁-N₃PS/HC exhibits outstanding alkaline ORR activity with a half-wave potential of 0.920 V and superior ORR kinetics with record-level kinetic current density and an ultralow Tafel slope of 31 mV dec⁻¹, exceeding that of Pt/C and almost all non-precious ORR electrocatalysts. In acidic media the ORR kinetics of Co₁-N₃PS/HC still surpasses that of Pt/C. This work offers atomic-level insight into the relationship between electronic density of the active site and catalytic properties, promoting rational design of efficient catalysts.