TiO2-WO3 composite nanotubes from co-sputtered thin films on si substrate for enhanced photoelectrochemical water splitting

Electrochemical anodization of a Ti-W nano-composite thin films deposited on a Si substrate by simultaneous magnetron sputtering of Ti and W resulted in the formation of TiO2-WO3 nanotubular arrays. A change in the morphology of TiO2-WO3 composite nanotubes with varying percentage of W in Ti-W composite thin films was observed. With a W density of less than or equal to 1.75 × 1019 W atoms per cm3 (after anodization), the morphology of the composite nanotubes were similar to that of plain TiO2 nanotubes. Whereas with further increase in W density resulted in a nanoporous morphology. Ti-W composite films were also deposited on Si substrates with a 100 nm thick layer of tin doped indium oxide (ITO) to examine the PEC activity of the formed oxide composites. The TiO2-WO3 composite nanotubes with 1.05 × 1019 W atoms per cm3 (3.15 × 1018 W atoms per cm3 before anodization) demonstrated to be an optimal W density for this system, giving rise to 40% increase in photocurrent at 0.5 V (vs. Ag/AgCl) compared to plain TiO2 nanotubes.