Enhancing Interfacial Capacitance by Boron Doping in Vertically Porous Carbon Toward High-Performance AC Filtering...

Electrochemical capacitors (ECs) show great perspective in alternate current (AC) filtering once they simultaneously reach ultra-fast response and high capacitance density. Nevertheless, the structure-design criteria of the two key properties are often mutually incompatible in electrode construction. Herein, it is proposed that combining vertically oriented porous carbon with enhanced interfacial capacitance (C_i) can efficiently solve this issue. Theoretically, the density function theory calculation shows that the C_i of a carbon electrode can be enhanced by boron doping due to the corresponding compact induced charge layer. Experimentally, the vertical-oriented boron-doped graphene nanowalls (BGNWs) electrodes, whose C_i is enhanced from 4.20 to 10.16 µF cm^-2 upon boron doping, are prepared on a large scale (480 cm²) using a hot-filament chemical vapor deposition technique (HFCVD). Owing to the high C_i and vertically oriented porous structure, BGNWs-based EC has a high capacitance density of 996 µF cm^-2 with a phase angle of - 79.4° at 120 Hz in aqueous electrolyte and a high energy density of 1953 µFV² cm^-2 in organic electrolyte. As a result, the EC is capable of smoothing 120 Hz ripples for 60 Hz AC filtering. These results provide enlightening insights on designing high-performance ECs for high-frequency applications.