Boosting capacitive performance of nitrogen-doped carbon by atomically dispersed iron

Carbon-based electrochemical capacitors are important energy storage devices owing to their high power and long life. However, their practical implementation has been restrained by low energy as a result of the limitation of double-layer capacitance. In this work, we demonstrate that the incorporation of atomically dispersed Fe into nitrogen-doped carbon (Fe−NC) can drastically boost the double-layer capacitance of carbon materials. Electrochemical tests reveal that an enhancement in the capacitance from 147.5 F g−1 to 174.8 F g−1 is realized when single Fe atoms are incorporated into nitrogen-doped carbon. In addition, symmetric supercapacitors based on Fe−NC exhibit a robust cycling performance, retaining 94.7% of the capacitance over 100,000 cycles. This improvement can be correlated to the chemical coordination of iron with adjacent nitrogen atoms to tailor the electric structure of carbon, which increases the density of states near the Fermi level and improves anion adsorption on atomic Fe sites. The single-atom engineering strategy may offer new possibilities to develop high-performance carbon materials for capacitors.