Origins of Boosted Charge Storage on Heteroatom-Doped Carbons.

Heteroatom-doped carbon materials have rapidly emerged as promising candidates for supercapacitor applications, owing to their tunable surface functionalities and exceptional performances. Although tremendous efforts have been devoted to understanding the origin of boosted charge storage on heteroatom-doped carbons, none of the present studies has shown a whole landscape. Herein, by both experimental evidence and theoretical simulation, we demonstrate that the heteroatom doping does not only result in a broadened operating voltage, but also successfully promotes the specific capacitance in aqueous supercapacitors. To be more specific, the electrolyte cations adsorbed on heteroatom-doped carbon can effectively inhibit hydrogen evolution reaction, a key step of water decomposition during the charging process, which broadens the voltage window of aqueous electrolytes even beyond the thermodynamic limit of water (1.23 V). In addition, the reduced adsorption energy of heteroatom-doped carbon consequently leads to more stored cations on the heteroatom-doped carbon surface, thus yielding a boosted charge storage performance.