B/P-Codoped Porous Carbon Electrode for Supercapacitors with Ultrahigh Energy Density

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 (PalA. Pal, A. ACS Appl. Energy Mater.202141081010825) 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 H3BO3, (NH4)2HPO4, or H3BO3/(NH4)2HPO4 in different amounts to obtain the doped materials. Further, 1.5 mmol H3BO3 (CPSM-1.5B) or (NH4)2HPO4 (CPSM-1.5P) or a mixture of 0.75 mmol H3BO3/0.75 mmol (NH4)2HPO4 (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 H2SO4 (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.

Ni Single Atom Decorated Porous Hollow Carbon Nanosphere‐Based Electrodes for High Performance Symmetric Solid‐State Supercapacitors

“…In addition to the mesopores, micropores are also generated in the samples at the high carbonization temperature as indicated by the sharp uptake of nitrogen in the low partial pressure region. [19] This is also reflected from the pore size distributions, where peaks could be seen below 2 nm. The pores in the samples are generated from the elimination of the triblock copolymer P123 and CTAB templates during the carbonization process as well as removal of silica after HF etching.…”

“…This may be ascribed to the improved wetting of the electrode surface during the consecutive cycling processes predisposing better a greater electroactive surface area. [19] Thus, the rapid transfer of electrolyte ions through the pores on the surface of the material is ensured and material stability is improved. After 9150 cycles, the retention of specific capacitance of the material has been found to be 93.5 %.…”

“…In the low frequency region of the Nyquist plots (Figure 8a), all the samples show steeper lines that are closely vertical to the real axis, signifying their good capacitive behaviour. [19] In the mid-frequency region, the lines have a slope of nearly 45°and give a measure of the diffusion resistance. The semi-circular portion observed in the high frequency region corresponds to the interfacial charge transfer resistance (R ct ).…”

“…In the preparation of porous carbonbased materials with high electrochemical performance, it is beneficial to incorporate heteroatoms into the carbon framework as they help in improving the specific capacitance. [13,14] Heteroatoms like boron, [15] nitrogen, [16] oxygen, [17] phosphorous [18] doping as well as co-doping of multiple heteroatoms [19] has the potential to enhance the faradaic reactions by improving both the surface wettability of the electrode and the conductivity of the carbon material. A further enhancement in faradaic pseudocapacitance can be brought about by the inclusion of a transition metal oxide.…”