Synthesis and characterization of highly ordered TiO2 nanotube arrays for hydrogen generation via water splitting

Highly ordered TiO2 nanotube arrays (TNA) have been synthesized by anodization of Ti foils using an established electrochemical process. The parameters such as anodization potentials and durations have been varied to fabricate the specific morphology of TNA. In addition, Pt nanoparticles were deposited on these TNA via microwave irradiation. The photocurrent density–voltage (J–V) properties induced by the standard AM 1.5 solar simulator have been characterized using a potentiostat meter. The efficiency of photoelectrocatalytic effect of the large-pore-sized TNA (=120 nm) is found to be higher than those of the TNA in smaller pore sizes (≤100 nm). TNA with smaller pore sizes exhibit lower surface areas, and therefore, inferior photo-current efficiency to those of TNA with larger pore sizes. The low surface area of smaller-pore-sized TNA was resulted from the shorter tube length obtained at smaller anodizing voltages. Deposition of Pt nanoparticles on TNA was successfully accomplished using microwave irradiation technique. An enhanced hydrogen generation rate of 0.613 ml h−1 cm−2 (≅25.0 μmol h−1 cm−2) was obtained on these Pt-deposited TNA compared to the 0.313 ml h−1 cm−2 (≅12.8 μmol h−1 cm−2) of pristine TNA in a solution of methanol and water (1:1 ratio).

► This work presents the fabrication route to achieve highly-ordered TiO2 nanotube arrays (TNA) by the established anodization process. The parameters such as anodization potentials and durations have been varied to fabricate the specific morphology of TNA. ► It was found that the crystalline anatase TNA with inner-diameter 120 nm exhibited higher photocatalytic effect than those of TNA with smaller inner diameter (≤100 nm) due to high surface area, easy access of water and exit flow of gas bubbles. ► It was confirmed that the smaller anodizing potential will result in smaller inner pore sizes and shorter tube lengths of TNA. ► Microwave irradiation process was a facile and effective method to deposit Pt nanoparticles on TNA. ► An enhanced hydrogen generation rate was obtained on these Pt-deposited TNA compared to that of pristine TNA in a solution of methanol and water (1:1 ratio).