Suppressing Water Electrolysis via Pb Single Atoms in Nitrogen-Doped Carbon for High-Energy-Density Supercapacitors

초록

Aqueous supercapacitors (SCs) are attractive energy storage devices owing to their high power density and operational safety; however, their practical deployment is constrained by the limited operating voltage window imposed by water electrolysis, which restricts the attainable energy density. Herein, we report a lead (Pb) single-atom anchored on nitrogen-doped carbon (SA-Pb/NC), where Pb, as a p-block metal, modulates the adsorption strength of H*/H2O species at Pb-N4 sites. Such modulation effectively suppresses water-electrolysis reactions, thereby expanding the electrochemical operational voltage window and enhancing energy storage performance. SA-Pb/NC delivers a specific capacitance of 530.07 F g-1, nearly twice that of bare NC. A symmetric SA-Pb/NC device further achieves an energy density of 38.67 Wh kg-1 within an ultrawide voltage window of 1.50 V. Remarkably, no detectable H2 evolution is observed for the SA-Pb/NC device even after 48 h of continuous operation, whereas the NC-based device generates 0.09 & micro;mol of H2 within only 12 h. Theoretical calculations further reveal that SA-Pb sites optimize K+ adsorption-desorption kinetics while weakening the affinity for H2O-derived intermediates, thereby enabling efficient charge storage and effective suppression of water electrolysis. This work provides a general strategy for designing high-energy-density aqueous supercapacitors through voltage-window expansion enabled by lead single-atom sites.

키워드