Hybridisation is a powerful strategy towards the next generation of multifunctional materials for environmental and sustainable energy applications. Here, we report a new inorganic/nanocarbon hybrid material prepared with atomically controlled deposition of a monocrystalline TiO2 layer that conformally coats a macroscopic carbon nanotube (CNT) fiber. Through X-ray diffraction, Raman spectroscopy and photoemission spectroscopy we detect the formation of a covalent Ti-O-C bond at the TiO2/CNT interface and a residual strain of approximately 0.7-2 %, which is tensile in TiO2 and compressive in the CNT. It arises after deposition of the amorphous oxide onto the CNT surface previously functionalized by the oxygen plasma used in ALD. These features are observed in samples of different TiO2 thickness, in the range from 10 to 80 nm. Ultraviolet photoemission spectroscopy on a 20 nm-thick TiO2 coated sample gives a work function of 4.27 eV, between that of TiO2 (4.23 eV) and the CNT fiber (4.41 eV), and the presence of new interband gap states that shift the valence band maximum to 1.05 eV below the Fermi level. Photoelectrochemical measurements demonstrate electron transfer from TiO2 to the CNT fiber network under UV irradiation. Electrochemical impedance spectroscopy measurements reveal a low resistance for charge transfer and transport, as well as a large capacitance. Our results point to the fact that these hybrids, in which each phase has nanometric thickness and the "current collector" is integrated into the material, are very different from conventional electrodes and can provide a number of superior properties.

The hybridisation of metal oxides and nanocarbons has created a promising new class of functional materials for environmental and sustainable energy applications. The performance of such hybrids can be further improved by rationally designing interfaces and morphologies. Atomic layer deposition (ALD) is among the most powerful techniques for the controlled deposition of inorganic compounds, due to its ability to form conformal coatings on porous substrates at low temperatures with high surface sensitivity and atomic control of film thickness. The hydrophobic nature of the nanocarbon surface has so far limited the applicability of ALD on CNTs. Herein we investigate the role of structural defects in CNTs, both intrinsic and induced by acid treatment, on coverage, uniformity and crystallinity of ZnO coatings. Furthermore, we demonstrate the potential of small aromatic molecules, including benzyl alcohol (BA), naphthalene carboxylic acid (NA) and pyrene carboxylic acid (PCA), as active nucleation sites and linking agents. Importantly, only PCA exhibits sufficiently strong interactions with the pristine CNT surface to withstand desorption under reaction conditions. Thus, PCA enables a versatile and non-destructive alternative route for the deposition of highly uniform metal oxide coatings onto pristine CNTs via ALD over a wide temperature range and without the typical surface corrosion induced by covalent functionalisation. Importantly, preliminary tests demonstrated that the improved morphology obtained with PCA has indeed considerably increased the hybrid's photocatalytic activity towards hydrogen evolution via sacrificial water splitting. The concept demonstrated in this work is transferable to a wide range of other inorganic compounds including metal oxides, metal (oxy)nitrides and metal chalcogenides on a variety of nanocarbons.

Gold-sulphur bonds holding self-assembled monolayers (SAMs) on their gold substrate can be broken by electrochemical reduction, which typically occurs in an electrode potential range where the electrochemical hydrogen evolution reaction (HER) is thermodynamically possible. This work uses an in situ coupling between cyclic voltammetry and spectroscopic ellipsometry to compare the interfacial structure after desorption of the aliphatic thiols 1-Dodecanethiol (DDT) and 1-Octadecanethiol (ODT), and the ω-hydroxythiol 11-Mercapto-1-undecanol (MUD). For MUD and DDT, the data can only be explained by the presence of a substance with a significantly lower refractive index than the aqueous electrolyte in the interfacial region. This substance is likely to be H2. The hypothesis is put forward here that for MUD and DDT, desorbed molecules stabilise "nanobubbles" of H2. The resulting aggregates form as initial stages of the process of complete disintegration of the SAMs, i.e. the loss of the SAM-forming molecules into solution. On the other hand, desorption and readsorption of ODT are fully reversible - the presence of a layer with low refractive index can neither be excluded nor confirmed in this case. The results indicate that different SAM-stabilities are a consequence of solubility of the thiolates.