钴单原子位点对碳基超级电容器电极倍率性能的动力学提升OA

To elucidate the influence of adjacent transition-metal single-atom sites on the energy-storage kinetics of carbon-based supercapacitor electrodes,Fe and Co single-atom-modified nitrogen-doped carbon materials,denoted as Fe@NC and Co@NC,were prepared using activated carbon as the carbon substrate via a metal-ligand coordination and carbonization strategy.Nitrogen-doped carbon without metal single-atom sites was used as the control sample.Structural characterizations reveal that NC,Fe@NC,and Co@NC possess similar carbon frameworks and porous structures,while Fe and Co species are highly dispersed and anchored in the nitrogen-doped carbon matrix,forming M-N4 coordination configurations.Electrochemical measurements show that Fe@NC and Co@NC deliver higher specific capacitances than NC,indicating that the introduction of metal single-atom sites can improve the charge-storage capability of carbon-based electrodes.Fe@NC and Co@NC exhibit comparable specific capacitances at current density of 1 A/g,with values of 106 and 109 F/g,respectively.When the current density increases to 20 A/g,Co@NC retains 55%of its capacitance,markedly higher than Fe@NC(38%),suggesting that Co single-atom sites are more favorable for improving high-rate capacitance retention.Further kinetic analyses demonstrate that Co@NC possesses a higher capacitive-controlled contribution,lower charge-transfer resistance,and more favorable ion-diffusion behavior,indicating that Co single-atom sites are more effective in facilitating rapid charge/ion transport.These results reveal that the rate-performance enhancement of carbon-based supercapacitor electrodes induced by metal single-atom sites mainly originates from optimized electrochemical kinetics,with Co single-atom sites showing greater advantages in promoting fast energy storage.This study provides mechanistic insight into the regulation of rate performance in carbon-based supercapacitor electrodes through single-atom site engineering.