Silicon oxycarbide-derived carbons from a polyphenylsilsequioxane precursor for supercapacitor applications

• Porous carbons were prepared by chlorination of silicon oxycarbides.
• Electronic and pore structure of carbon was controlled via synthesis temperature.
• EDLC electrodes were prepared with aqueous slurry and doctor blade technique.
• Resulting electrodes show high power and energy density.

In this study, we report on the preparation of new silicon oxycarbide-derived carbons (SiOCDC) obtained by pyrolysis and chlorination of a polyphenylsilsesquioxane pre-ceramic precursor. Wet-chemical conversion of phenyltrimethoxysilane (PhTMS) to the organosilica material was conducted using a two-step acid/base sol–gel process in aqueous medium. The resulting material was subsequently pyrolysed at 700, 1000 and 1300 °C to obtain a non-porous silicon oxycarbide ceramic. Chlorination at 700 and 1000 °C led to carbons having large surface areas exceeding 2000 m2 g−1 as well as large micro-/mesopore volumes up to 1.4 cm3 g−1. The temperature of the thermal treatment significantly influences the carbon and final pore structure. Pyrolysis at 700 °C and subsequent chlorination at 700 °C led to a mainly microporous material, whereas pyrolysis at 1300 °C and subsequent chlorination at 1000 °C generated a hierarchically porous SiOCDC with micro- and mesopores, respectively. All SiOCDC materials were prepared as supercapacitor electrodes using an aqueous slurry containing polytetrafluoroethylene (PTFE) and sodium carboxymethyl cellulose (CMC) as binder. With an organic electrolyte (1 M TEABF4 in acetonitrile) capacitances of up to 110 F g−1 and good long term stabilities could be observed.

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