Synthesis of photocatalytic hematite nanotube array using a template-free solvothermal approach

Abstract

The paper describes a template-free solvothermal synthesis of α-Fe₂O₃ hollow nanotube arrays over a large area. The columnar nanotubes on the substrate have closed tips and smooth defined walls. The thickness of the nanowall is about 10 nm, which could offer short diffusion distances and decrease recombination of electron–hole pairs. And the preferential orientation is the [110] axis. The cubic Au nanocrystals were decorated by a photocatalytic reduction process, and the corresponding EDX mappings intuitively display the distributions of the composites. Au nanocrystals matched the absorption of α-Fe₂O₃ hollow nanotube arrays, which improved photoactivity under visible light (wavelength > 420 nm). The photoactivity of the sample was investigated based on systematic photoelectrochemical (PEC) measurements. These revealed that the photocurrent density of Au/α-Fe₂O₃ is almost 6 times higher than that of pure α-Fe₂O₃. And its photocurrent density increases to 0.16 mA cm⁻² at 1.23 V_RHE under irradiation. The mechanism of enhanced visible light PEC activity has been discussed using schematics. Hence, the study presents not only a route for formation of α-Fe₂O₃ hollow nanotube arrays but also PEC applications of plasmonic composites.