Correlation between self-discharge behavior and heteroatoms over doped carbon sheets for enhanced pseudocapacitance

For electric double layer supercapacitors, carbon materials originating from the purely physical energy-storage mechanism limit the improvement in the capabilities of charge storage. To solve this problem, doping heteroatoms into carbon skeleton is a promising & charming strategy for enhancing electrochemical performance by providing the extra pseudocapacitance. However, the self-discharge behavior of such heteroatom-doped supercapacitors has been a challenging issue for a long time. Here, the porous carbon nanosheets with a tunable total content of heteroatoms are chosen as a demo to systemically decouple the correlation between the total content of heteroatoms and the specific capacitance as well as the self-discharge behavior. The capacitance changes in a range of 164–331 F g−1 @ 1 A g−1 with the increased total contents of doped heteroatom, strongly dependent on and sensitive to the total content of heteroatoms. The voltage retention rate and capacitance retention rate for the porous carbon nanosheets with a tunable total content of heteroatoms completely present a quick decline tendency as the increase in the content of heteroatoms, changing from 58% to 34% and 74% to 39%, respectively, indicative of a linear negative relationship. More importantly, the self-discharge mechanisms are elaborately explored and follow the combination of activation- and diffusion-controlled Faradic reactions. This work illustrates the diverse impacts of the doped heteroatoms on the electrochemical performance of supercapacitors, covering specific capacitance and self-discharge behavior, and highlights the importance of balancing the contents of doped heteroatoms in energy storage fields.