Preparation Of Carbon Materials From Protic Ionic Liquids For High-performance Electrodes In Supercapacitors

Heteroatom porous carbon materials have been widely used in analysis,catalysis,energy storage and other fields owing to their excellent characteristics such as low cost,high chemical stability,and large specific surface area.However,heteroatom porous carbon materials have unique advantages as electrode materials for supercapacitor.The electrochemical performance of supercapacitor electrode material is directly related to the pore structure,the surface/bulk functional group?chemical modification or doping?,and the conductivity,etc.Nevertheless,the precursors and methods for preparing heteroatom porous carbon materials still face various defects at present:?1?the synthesis of carbon precursors is complex leading to high energy consumption in the preparation of heteroatom-doped carbon materials and the molecular composition is not fixed,causing the uncontrollable heteroatom content and species;?2?the method for preparing heteroatom-doped carbon materials is cumbersome and time-consuming,and the pore of the prepared carbon material is single;?3?the process of preparing heteroatom-doped carbon materials causes serious environmental pollution.Therefore,how to facilely and greenly prepare heteroatom-doped porous carbon materials with high performance and hierarchically porous structure is a big challenge.In this paper,the protic ionic liquids of phenothiazine and glucosamine?a derivative of glucose?were chose as precursors to prepare N/S codoping carbon materials with different structures by diverse methods.The effects of heteroatom doping and different pore structures for carbon materials on the electrochemical performance of supercapacitors were systematically studied.Specific work is as follows:?1?Protic ionic liquid derived nitrogen/sulfur-codoped carbon materials as high-performance electrodes for supercapacitor.In this study,the protic ionic liquid of phenothiazine?[Phne][HSO₄]?containing the elements of N,S in molecular structure was used as raw material to prepare high-capacitance carbon electrode material for supercapacitor.The[Phne][HSO₄]was pyrolyzed at 700 ^oC,and then activated by KOH at 700 ^oC,showing high surface area,large pore volume and high N,S content?N:3.41 at.%,S:6.65 at.%?.The optimal sample displays excellent electrochemical performance of 430 F g^-11 at the current density of 0.2 A g^-11 in 6M KOH.The rich micropores effectively provide double layer capacitance and the synergistic effect of N,S doping enhances the conductivity of carbon materials while providing pseudocapacitance,which are all conducive to improve the capacitive performance of carbon materials.?2?Double soft-template synthesis of nitrogen/sulfur-codoped hierarchically porous carbon materials derived from protic ionic liquid for supercapacitor.In this experiment,the[Phne][HSO₄]was not only used as carbon source,nitrogen source and sulfur source,but also microporous porogen due to the release of NH₃,SO₂ and H₂O,producing part of micropores during pyrolysis.F127,OP-10 respectively used as mesoporous and macroporous template can be directly removed to form mesoporous and macroporous under high temperature condition.Thus,N/S-codoped hierarchical porous carbon materials can be prepared by one step.The ratio of[Phne][HSO₄],F127 and OP-10 at 15:20:1 can obtain the best electrochemical performance electrode carbon material.The acquired carbon materials for supercapacitor not only hold a large specific capacitance of 302 F g^-1even at 1.0 A g^-1,but also fine rate property with 169 F g^-11 at 10 A g^-11 and excellent capacitance retention of nearly 100%over 5000 circulations in 6 M KOH electrolyte.Furthermore,carbon materials also present eximious rate performance with 70%in 1 M Na₂SO₄ electrolyte.?3?Solvent-free synthesis of N/S-codoped hierarchically porous carbon materials from protic ionic liquids for temperature-resistant,flexible supercapacitor.In this study,the protic ionic liquid of meglumine?a derivative of glucose??[Megl][HSO₄]?was used as raw material and microporous porogen.F127 and sodium dodecyl sulfate were used as mesoporous template and macroporous template,respectively.The N/S-codoped hierarchically porous carbon materials with the combination of hollow carbon nanospheres and the folded structure was prepared by a simple and environmentally friendly approach of pretreating the solid mixture of[Megl][HSO₄],F127 and sodium dodecyl sulfate in a Teflon-lined stainless-steel autoclave and then pyrolyzing at high temperatures.Different structures and electrochemical properties of N/S-codoped hierarchically porous carbon materials were obtained by adjusting the pretreatment temperature and pyrolysis temperature.The vintage electrochemical properties for supercapacitor of carbon materials can be prepared at the pretreatment temperature of 160 ^oC and pyrolysis temperature of 900 ^oC.In 6 M KOH,the specific capacitance of the acquired carbon materials for supercapacitor can reach 347 F g^-11 at the current density of 0.5 A g^-1,and still hold 174 F g^-11 even at the current density of 20 A g^-1,and excellent capacitance retention of nearly 100%over 5000 circulations.More importantly,the 16-N/S-HPC₉₀₀00 still maintains excellent electrochemical properties and stability under the condition of extreme temperatures?-20 ^oC¹00 ^oC?and bending?0^o180^o?.The double soft-template,solvent-free self-assembly approach provides new insight for facilely and environmentally-friendly preparing heteroatom-doped porous carbon materials with micropores,mesopores and macropores for the energy storage applications.