Nanostructured carbon substrate improves the photoelectrochemical water splitting activity of cluster-assembled TiO2 thin films

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-TiO2) 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:TiO2 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 TiO2 photoelectrodes deposited by the same technique and featuring the same TiO2 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.