A General Method for Transition Metal Single Atoms Anchored on Honeycomb-Like Nitrogen-Doped Carbon Nanosheets

Excavating and developing highly efficient and cost-effective nonnoble metal single-atom catalysts for electrocatalytic reactions is of paramount significance but still in its infancy. Herein, reported is a general NaCl template-assisted strategy for rationally designing and preparing a series of isolated transition metal single atoms (Fe/Co/Ni) anchored on honeycomb-like nitrogen-doped carbon matrix (M-1-HNC-T-1-T-2, M = Fe/Co/Ni, T-1 = 500 degrees C, T-2 = 850 degrees C). The resulting M-1-HNC-500-850 with M-N-4 active sites exhibits superior capability for oxygen reduction reaction (ORR) with the half-wave potential order of Fe-1-HNC-500-850 > Co-1-HNC-500-850 > Ni-1-HNC-500-850, in which Fe-1-HNC-500-850 shows better performance than commercial Pt/C. Density functional theory calculations reveal a choice strategy that the strong p-d-coupled spatial charge separation results the Fe-N-4 effectively merges active electrons for elevating d-band activity in a van-Hove singularity like character. This essentially generalizes an optimal electronic exchange-and-transfer (ExT) capability for boosting sluggish alkaline ORR activity. This work not only presents a universal strategy for preparing single-atom electrocatalyst to accelerate the kinetics of cathodic ORR but also provides an insight into the relationship between the electronic structure and the electrocatalytical activity.