Microstructure-electrochemical behavior relationships of hierarchically micro-mesoporous silicon oxycarbide derived materials obtained by the pyrolysis of trietoxysilane/dimethyldiphenylsiloxane hybrids

Highlights: • Hierarchically micro-mesoporous SiOC-CD were obtained from HF etching of SiOC • Better electrochemical response when both micro and slit-shape mesopores are present • SiOC-DC materials pyrolyzed at 1200 °C display a C_s of up to 100 Fg⁻¹ at 40 Ag⁻¹ • SiOC-DCmaterials pyrolyzed at 1200 °C show an energy density of up to 28 W h Kg⁻¹ -- Abstract: Hierarchically micro/mesoporous silicon oxycarbide derived carbon (SiOC-DC) materials have been successfully prepared by HF selective removing of silica nano-domains present in SiOC. Dense carbon enriched SiOC materials are obtained by pyrolysis from 1100 to 1400 °C of novel sol-gel hybrids which contain both Si–H and Si-Ph bonds. The pyrolysis temperature deeply affects the etching process, major differences are observed between the sample pyrolyzed at 1100 °C and at higher temperatures. Those differences are directly associated to the evolution of the phase separation of SiOC into SiO₂ and SiC, which facilitates the selective extraction of silica nano-domains and the formation of micro/mesoporous SiOC-DC materials with high specific surface areas (SSAs) and high pore volumes. The SiOC-DC sample pyrolyzed at 1200 °C displays very promising results of specific capacitance (90–100 Fg⁻¹ at 40 Ag⁻¹), relatively high energy density (28 W h Kg⁻¹) at a low power density (0.10 kW kg⁻¹), and a significant performance at high power density (10 W h Kg⁻¹ at 49 kW kg⁻¹), taking into account the low potential window of inorganic liquid electrolyte used (0.9 V). We have found that the presence of micropores but even more, the presence of slit-shape mesopores (D_meso 3–10 nm) is crucial in order to explain the electrochemical response of these materials.