Highly Microporous Nitrogen-Doped Carbon Derived from Silicon Oxycarbide Ceramics for Supercapacitor Application

Highly microporous nitrogen-doped silicon oxycarbide (SiOC) derived materials were obtained by solvothermal process of vinyltriethoxysilane in urea solution and followed by HF etching. SiOC ceramics synthesized at 1200 o C exhibits good chemical durability in HF solution due to the formation of more SiO 2 C 2 unit. Increasing the pyrolysis temperature not only increases the specific surface area and pore volume of SiOC derived materials, but also generates more pyridinic N and pyrrolic N functionalities. Furthermore, after HF etching, only incorporation of fluorine in SiOC ceramics (F − Si bond) and no C − F bond is found. The phase separation occurs during the pyrolysis process, and the generation of SiC is mainly caused by the carbothermal reduction reaction between SiO 2 and free C (C free ). The thermogravimetric analysis shows the oxidation resistance of SiC is superior to that of SiOC and C, while SiOC has better thermal stability than C. Both the high specific surface area, micropore volume and N-doping contribute the good supercapacitor performance. SiOC derived carbon materials with a high specific surface area of 1109.0 m 2 g − 1 and pore volume of 0.77 cm 3 g − 1 exhibit the specific capacitance of 272.2 Fg − 1 at the current density of 0.2 Ag − 1 in 6 M KOH aqueous electrolyte and good cycling stability of 89.7% retention after 10,000 cycles at 5 Ag − 1 . In addition, the specific capacitance can reach up to 33.2 F g − 1 at 0.2 A g − 1 for a symmetrical supercapacitor, and a stable capacitance of 29.1 F g − 1 retains over 6000 cycles at 1 A g − 1 .