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The supersonic cluster beam deposition (SCBD) of titanium oxide nanoparticles is a versatile and effective bottom-up approach for the fabrication of nanostructured titanium dioxide (ns-TiO 2 ) thin films; here we report on its application to the production of photoelectrodes for photoelectrochemical water splitting. The use of a cluster-assembled carbon (ns-C) thin film deposited by SCBD as a substrate layer for the titania nanoparticles deposition is also investigated and demonstrated to originate C:TiO 2 nanocomposite photoelectrodes with increased surface roughness and more than four-fold enhanced IPCE (ca. 4.5% under monochromatic illumination at 330 nm employing KOH 1 M as aqueous electrolyte solution and without any external bias) compared to pure TiO 2 photoelectrodes deposited by the same technique and featuring the same TiO 2 thickness (ca. 250 nm). Electrochemical impedance spectroscopy (EIS) has been used to correlate the increase of the IPCE to an optimized electrode structure, electrolyte accessibility and electric conductivity. These results are promising towards the practical use of nanoparticle-assembled materials and the improving of their properties.

Nanostructured carbon sp(2) (ns-C) thin films with up to 30% of sp-coordinated atoms (carbynes) were produced in a high vacuum by the low kinetic energy deposition of carbon clusters produced in the gas phase and accelerated by a supersonic expansion. Immediately after deposition the ns-C films were immersed in situ in an ionic liquid electrolyte. The interfacial properties of ns-C films in the ionic liquid electrolyte were characterized by electrochemical impedance spectroscopy and cyclic voltammetry (CV). The so-prepared carbyne-rich electrodes showed superior electric double layer (EDL) capacitance and electric conductivity compared to ns-C electrodes containing only sp(2) carbon, showing the substantial influence of carbynes on the electrochemical properties of nanostructured carbon electrodes.