Institut für Materialchemie, Technische Universität Wien, Vienna, Austria
In this lecture I will discuss the main challenges in heterogeneous photocatalysis and present two materials design strategies.
What are nanocarbon-inorganic hybrids? Hybridising nanocarbon materials, i.e. CNTs and graphene, with active inorganic nanomaterials constitutes a powerful strategy towards designing new-generation functional materials for many applications where efficient charge separation and extraction is required, including photovoltaics, photocatalysis, batteries, supercapacitors and biosensors. In contrast to nanocomposites, which merely combine the intrinsic properties of both compounds, nanocarbon hybrids additionally provide access to both a large internal active surface area required for gas/liquid-solid interactions and an extended interface, through which charge and energy transfer processes create synergistic effects that result in unique properties and superior performances.
How can they be improved? I will demonstrate that the performance of these hybrids can be further enhanced through purposefully engineering interfaces and morphology, e.g. fewer grain boundaries alleviate electron transport within the catalyst and the formation of an Ohmic junction facilitates charge transfer and charge separation at the interface with the nanocarbon.
How do they function? I will present a model system that allows for measuring and tuning of interfacial charge and energy transfer processes and for revealing the nature of catalytically active sites in nanocarbon hybrids.
What is mesotructuring? The next aim is to design photocatalysts (in particular hybrid photocatalysts) with large 3D-connected pores and ordered mesopore architectures. This should eliminate kinetic restrictions imposed by pore diffusion and allow ready gas and liquid access to all active sites. We design these materials through a self-assemble- assisted process using tailor-made triblock-terpolymers as structure-directing agents and sacrificial templates.
Fig: a) Working princliple of nanocarbon-inorganic hybrid photocatalyst; b) model system with dielectric barrier layer (Al2O3) between a photoactive ZnO shell and CNT inner core; b) ordered mesoporous carbon with gyroid architecture.