Precursor derived nanostructured carbon ceramic hybrids for hydrogen storage

Abstract

Polymer-derived-ceramics (PDC) possess excellent physico-chemical characteristics, including creep resistance, piezoresistivity, Li ion intercalability, and are processed from the inert pyrolysis of Si-containing polymers. However, during pyrolysis, escape of organic moieties followed by sintering results in low specific surface area (SSA) of the particulate ceramics. Immense prospects lie for the use of these materials in the areas of adsorption, storage and separation of gases (H2, CH4) if the SSA and porosity can be tailored to desired levels. The current work explores a novel, yet versatile, method for the fabrication of a hybrid with a nanostructured carbon as a template and the PDC as coating. The carbon template limits shrinkage of the PDC leading to SSA of >250 m2/g, and average pore size <1.5 nm. Retention of such high SSA and microporosity are important properties for sensing and adsorption. Furthermore, the PDC silicon oxycarbide coating constitutes of nanostructured SiO2 domains that can be leached out to enhance SSA to fabricate highly porous oxycarbide derived carbon. Such carbon materials have shown SSA in excess of 916 m2/g with a major part of the porosity being microporous. Interestingly the process is so generic that with subtle change in process parameters, the SSA and pore size can be tailored. HRTEM imaging of the hybrids have shown graphene-type carbon layers and clearly observable microporosity. Initial results of hydrogen uptake of these hybrids have shown encouraging results. The interplay of process parameters on the evolution of nanoporosity and nanostructure of the hybrids materials will be presented.