Electrodeposition-assisted formation of anodized TiO2-CuO heterojunctions for solar water splitting

The anatase phase titanium dioxide nanotubes (ATNTs) are investigated for photocatalytic water splitting with and without the formation of copper oxide (CuO) heterojunctions. ATNTs have been grown on titanium substrate by one- and two-step anodization, followed by annealing at 450 oC for transformation to anatase phase. Anodization was performed in an electrolyte containing ammonium fluoride, ethylene glycol and deionized water. The ATNTs were then modified with CuO nanoparticles by dip-coating and electrochemical deposition. The growth of ATNTs and incorporation of CuO nanoparticles in it were confirmed with X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and energy-dispersive X-ray (EDX) spectroscopy. Well-organized and vertically aligned nanotubes were observed in the FESEM results. Contact angle measurements proved that the thin film of nanotubes is hydrophilic in nature. Linear sweep voltammetry (LSV) technique was performed for photocurrent responses, using distilled water in the dark environment as well as in the light of solar simulator at applied potential of 1.0 V. The photocurrent densities in the dark were negligible, while it became significant under the influence of simulated visible light. The ATNTs grown with two-step anodization offered promising results for photocatalytic water splitting compared to single-step anodization. The CuO modification in ATNTs exhibited a reasonable increase in photocurrent densities compared to pristine ATNTs. Furthermore, the electrochemical deposition process for modification of ATNTs with CuO afforded much better photocurrent responses compared to the dip coating method. The electrochemical deposition of CuO in ATNTs was performed at 0.7 V, 0.9 V and 1.1 V, among which the sample prepared at 0.7 V exhibited the highest photocurrent densities.

Automated summary

The anatase phase titanium dioxide nanotubes (ATNTs) were grown on titanium substrate by one- and two-step anodization, followed by CuO modification for photocatalytic water splitting. The two-step anodization of ATNTs showed superior results compared to single-step anodization, with CuO modification leading to increased photocurrent densities. Electrochemical deposition of CuO in ATNTs was more effective in enhancing photocurrent responses than the dip coating method, with the sample prepared at 0.7 V exhibiting the highest photocurrent densities.