Hierarchical Phenolic Resin-based Carbons with High Surface Area and Pore Volume Obtained by Soft-templating and Activation

Introduction Advanced applications often require carbons with high surface area and hierarchical porous structures. In response to this demand some efforts have been undertaken to create materials, which effectively combine the properties of both activated carbons (high surface area) and ordered mesoporous carbons (tunable and well-developed porosity). While there are activation methods, which have been successfully used to generate micropores, the preparation of pores in the mesopore range is more challenging. The first ordered mesoporous carbons were obtained by hard templating (nanocasting) method [1,2], where the pores of sacrificial hard template (usually ordered mesoporous silica or colloidal silica) were filled with a carbon precursor, which after carbonization and subsequent template dissolution resulted in the final carbon material. The main drawback of this method is the preparation of the hard template followed by its removal, which increase the time and cost of the entire fabrication route. In contrast, the recently established soft-templating method [3-5] utilizes thermally-decomposable triblock copolymers as soft templates and the thermosetting polymers as carbon precursors. During initial heating the thermally unstable copolymer is removed, while the thermosetting polymer is carbonized by high temperature treatment under neutral atmosphere. This approach was proved to be successful not only in terms of simplifying and shortening the preparation of ordered mesoporous carbons but also in terms of versatility of other carbon-based materials, which could be prepared. The most interesting aspect of the soft-templating synthesis is surprisingly high tolerance of carbon precursor/block copolymer system to accommodate foreign species without substantial deterioration of porous structure of the final carbon-based material [6-7]. This feature can be adapted in the preparation of wide range of organic-inorganic nanocomposites or carbons possessing different pore geometries. Here we report the soft-templating synthesis of phenolic resin-based carbons possessing the hierarchical architecture of pores. Taking advantage of the possibility of introducing large amounts of inorganic species the synthesis was conducted in the presence of tetraethyl orthosilicate (TEOS) and silica colloids. Since the as-prepared carbons were mainly mesoporous the post-synthesis activation was employed to develop additional microporosity. The resulting hierarchical carbons, composed of small micropores of about 2nm, the primary mesopores of about 12nm and bigger mesopores resembling the size of the silica colloids used, exhibited high BET surface area reaching 2200m/g and the pore volume up to ~6.0cm/g.