Carbonaceous catalysts for photocatalysis and electrocatalysis with high specific surface by direct carbonization of hierarchical block copolymer architectures

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Carbonaceous hybrid materials have considerable potential as support and catalyst in photocatalysis and electrocatalysis. Aim of the proposed project is integration of carbonaceous hybrid materials into three-dimensional hierarchical architectures to combine intrinsic advantages of carbonaceous hybrid materials and of three-dimensional hierarchical architectures, such as high surface area and facile access to catalytically active sites. Two target architectures will be realized and tested: optically transparent self-ordered nanoporous anodic alumina (AAO) membranes containing carbon/titania (C-TiO2) nanotubes for visible-light photocatalysis and arrays of freestanding mesoporous carbon/metal nanoparticle (C-NP) nanorods for electrocatalysis obtained by replicating AAO. Both target architectures will be characterized by significantly higher specific surface than smooth thin-film configurations; access to catalytically active sites will be significantly improved as compared to conventional mesoporous materials. To prepare the target architectures, a new approach developed by Steinhart and Kim, direct carbonization of nanostructured block copolymers (BCPs), will be applied.The hierarchical level introduced by the AAO pores comprises the topographic contour of the C-TiO2 nanotubes and the mesoporous C-NP nanorods. C-TiO2 nanotubes for visible-light photocatalysis in AAO membranes have ~1000 times larger surface per membrane area than smooth thin-film configurations. This architecture minimizes catalytically ineffective light absorption by carbon since only thin C-TiO2 layers cover the pore walls of the transparent AAO membranes. TiO2 nanotubes in AAO can potentially be used as photocatalytic component in flow reactors. The topographic contact interface of mesoporous C-NP nanorods to electrolyte solutions is 11 times larger than that of smooth mesoporous C-NP films. The hierarchical level related to the nanoscopic BCP domain structure directs the spatial distribution of TiO2 in C-TiO2 nanotubes covering the AAO pore walls. It also directs swelling-induced morphology reconstruction yielding continuous mesopore systems in BCP nanorod arrays that will be converted into mesoporous C-NP nanorod arrays. The photocatalytic performance of TiO2 nanotubes in AAO and the electrocatalytic performance of mesoporous C-NP nanorod arrays will be tested in comparison to smooth control samples by means of selected model reactions.