Ionothermal Synthesis of Carbon/TiO₂ Nanocomposite for Supercapacitors

Abstract

A facile in-situ ionothermal strategy is designed to synthesize carbon/oxide composites with nanoporous structure. Ionic liquids play key roles in this ionothermal method as the solvents, porous structure directing templates and carbon sources. The interaction between ionic liquids and oxides greatly improves the carbon yield of ionic liquids from nearly 0 to 18 wt.%. With the synergistic effects of the high electrical conductivity of the nitrogen-rich carbon species and the Ti 3 + self-doping enhanced electrical conductivity of TiO 2 , C/TiO 2 -4 composite exhibits better electrochemical performance than C/SiO 2 and C/Nb 2 O 5 do as a supercapacitor electrode material, delivering a high specific capacitance of 152.4 F g À 1 at 5 mV s À 1 with good capacitance retentions of 84.7%, 72.2% and 46.0% at 30, 100 and 500 mV s À 1 , respectively.

Facile and Tunable Synthesis of Nitrogen-Doped Graphene with Different Microstructures for High-Performance Supercapacitors

“…Moreover, Raman spectroscopy was applied to study the structural features those two materials (Figure d). For the BNG, the peak at around 1341 cm –1 can be corresponded to the disorder-induced band of the sp 3 -hybridized graphitic carbon (D band), and the peak at about 1581 cm –1 is ascribed to the in-plane vibrations of the sp 2 -hybridized carbon of graphite (G band) . Interestingly, the G band of pristine G prepared by the CVD method is located at 1583–1588 cm –1 , while the peak position of the G band in this study presents a blue shift.…”

“…More interestingly, the heteroatom-doped carbon not only offers electrical double layer capacitance but also introduces pseudocapacitance through the superficial redox reactions of the doped heteroatoms with the electrolyte, further enhancing the energy density of the supercapacitor . For instance, some previous literature suggests that the nitrogen-doped carbon materials can deliver pseudocapacitance to enhance the energy density. − The introduced nitrogen atoms with abundant pairs of lone electrons can act as a Lewis base to interact with cations in the electrolyte, which enables the pseudocapacitance contribution for energy storage. However, the aforementioned approaches are complicated and involve synthesizing catalyst compounds separately before placing the carbon source into the confine space of catalysts.…”

“…31 Generally, the relative areal ratio of the D band to the G band (I D /I G ) can be used as indicator for graphitization degree. 24 For BNG, the I D / I G is calculated to be 1.39. In sharp contrast, SNG exhibits an I D /I G value of 1.18, less than that of BNG, indicating the BNG has more exposed surface area for charge storage.…”

“…For the BNG, the peak at around 1341 cm −1 can be corresponded to the disorder-induced band of the sp 3 -hybridized graphitic carbon (D band), and the peak at about 1581 cm −1 is ascribed to the in-plane vibrations of the sp 2 -hybridized carbon of graphite (G band). 24 Interestingly, the G band of pristine G prepared by the CVD method is located at 1583−1588 cm −1 , 28 while the peak position of the G band in this study presents a blue shift. This is in line with a reported N-doped carbon nanotube material in the literature, confirming the successful N doping, which is rooted in the Nrich starting reagents.…”

“…A small fitted peak located at 1680 cm –1 is the D′ band, corresponding to the defect induced peak associated with disorder in graphene . Generally, the relative areal ratio of the D band to the G band (I D /I G ) can be used as indicator for graphitization degree . For BNG, the I D /I G is calculated to be 1.39.…”