Interfacial studies in CNT fibre/TiO2 photoelectrodes for efficient H2 production

An attractive class of materials for photo(electro)chemical reactions are hybrids based on semiconducting metal oxides and nanocarbons (e.g. carbon nanotubes (CNT), graphene), where the nanocarbon acts as a highly-stable conductive scaffold onto which the nanostructured inorganic phase can be immobilised; an architecture that maximises surface area and minimises charge transport/transfer resistance. TiO2/CNT photoanodes produced by atomic layer deposition on CNT fabrics are shown to be efficient for H-2 production (0.07 mu mol/min H-2 at 0.2 V vs Ag/AgCl), nearly doubling the performance of TiO2 deposited on planar substrates, with 100% Faradaic efficiency. The results are rationalised based on electrochemical impedance spectroscopy measurements showing a large reduction in photoelectron transport resistance compared to control samples and a higher surface area. The low TiO2/CNT interfacial charge transfer resistance (10 Omega) is consistent with the presence of an interfacial Ti-O-C bond and corresponding electronic hybridisation determined by spatially-resolved Scanning Photoelectron Microscopy (SPEM) using synchrotron radiation.