Regulating the π-π interaction with shortened electron tunneling distance for efficient charge storage

Coupling organic redox moieties with carbon through π–π interaction is a widely used strategy to boost the energy densities of electrochemical capacitors, but the low electron tunneling probability of π–π interaction through the out-of-plane direction intrinsically limits the charge storage capacity and rate capability. Here we rationally construct B involved functional sites on the surface of porous carbon fibers for coupling hydroquinone (HQ) molecules with enhanced π–π interaction, which enables exceptional charge storage performance by regulating the interfacial charge tunneling behavior. The designed HQ-carbon composites deliver an attractive areal capacitance of 2.68 F cm −2 at 2 mA cm −2 and retain 2.10 F cm −2 at 40 mA cm −2 , representing the highest areal capacitance among the ever-reported organic redox moiety/carbon systems. Meanwhile, maximum volume energy density and power density of 12.2 mWh cm −3 and 3683 mW cm −3 are demonstrated by assembling an asymmetric supercapacitor with Ti 3 C 2 T x . The theoretical calculation indicates the decreased tunneling distance originating from the regulated π–π interaction contributes to the fast kinetics of proton-involved charge-storage process. The capability of regulating the charge transfer behavior offers a new vision to couple organic redox moieties with carbon for energy storage and beyond.