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