Aluminum titanate-based nanocomposite layers in photoelectrochemical water splitting under visible light

Although Al₂TiO₅-based nanocomposites are known to be promising photocatalysts, their potential application in photoelectrochemical (PEC) water splitting has not yet been explored. In this study, innovative photoanodes composed of TiO₂/Al₂TiO₅/Al₂O₃ nanocomposite powders were developed. These powders were synthesized via sol-gel method and deposited on fluorine-doped tin oxide (FTO) substrates. The crystalline phase ratio in these nanocomposites was controlled by adjusting the calcination temperature between 800 and 1000 °C, and then identified by the X-ray diffraction analysis. The microstructure properties of the samples were examined by Field-emission scanning electron microscopy. UV–Vis spectroscopy and Mott-Schottky analyses were employed to determine the bandgap energies and band edge positions of the materials. For the TiO₂/Al₂TiO₅/Al₂O₃ nanocomposites, the bandgap values were found to range from 2.9 to 3.1 eV. Photoluminescence analysis indicated a reduced electron-hole pair recombination rate in tialite-based photoanodes compared to TiO₂ films. Electrochemical impedance spectroscopy (EIS) showed that the sample with the highest tialite (Al₂TiO₅) concentration had significantly lower charge transfer resistance. Due to the relative positions of the band edges in this composite, photogenerated holes can be injected from the valence band of other photocatalyst phases into the valence band of Al₂TiO₅ and then transferred to the electrolyte, contributing to the photoelectrochemical water oxidation reaction. Under illumination of 100 mW cm⁻², the photocurrent density of the AT-based photoelectrodes reached 0.42 mA cm⁻² at 1.23 V versus the reversible hydrogen electrode, which was approximately 2.5 times higher than that of the TiO₂ sample.