B/P-Codoped Porous Carbon Electrode for Supercapacitors with Ultrahigh Energy Density
Manjula Pal, Ananya Pal, Prashanta Pal, Mahasweta Nandi
Abstract
A series of B-, P-, and B/P-codoped carbon samples have been synthesized by carbonization of a phloroglucinol-salicylaldehyde-melamine ( PSM@silica )-based polymer/silica composite under a nitrogen environment at 900 °C. Carbonization of PSM@silica under identical conditions and without any external doping has been reported previously by our group ( Pal, A.; ACS Appl. Energy Mater. 2021, 4, 10810–10825) to yield N/O-doped spherical carbon particles ( CPSM-900 ) with remarkable electrochemical properties. In order to investigate the effect of heteroatom doping from an external source, PSM@silica has been mixed with H 3 BO 3, (NH 4 ) 2 HPO 4, or H 3 BO 3 /(NH 4 ) 2 HPO 4 in different amounts to obtain the doped materials. Further, 1.5 mmol H 3 BO 3 ( CPSM-1 . 5B ) or (NH 4 ) 2 HPO 4 ( CPSM-1 . 5P ) or a mixture of 0.75 mmol H 3 BO 3 /0.75 mmol (NH 4 ) 2 HPO 4 ( CPSM-0 . 75 B /0 . 75P ) afforded the best materials where the heteroatom content increased from CPSM-1 . 5B (7.0%) to CPSM-1 . 5P (11.0%) to CPSM-0 . 75B /0 . 75P (13.9%). The doped samples retain spherical morphology and a high surface area, as does CPSM-900 without any external doping. However, a drastic enhancement is observed in the electrochemical properties of the doped samples, which parallels the heteroatom content. The specific capacitance of CPSM-0 . 75B /0 . 75P reaches 1046 F/g at a current density of 0.6 A/g in 1 M H 2 SO 4 (which is 400 F/g for CPSM-900 ) with very high power (270 W/kg) and energy density (118 Wh/kg) values, thereby bridging the gap between conventional supercapacitors and batteries. It has been illustrated that a symmetric device constructed with the material can illuminate a green light-emitting diode (LED) bulb of 3 V, and it can be recharged and reused indicating its sustainable energy-storage capability.