Noble-Metal-Free Modified TiO2 Nanotube Arrays (TNTAs) for Efficient Photocatalytic Reduction of CO2 to CO Under Visible Light

In the past decades, TiO2 nanotube arrays (TNTAs) have gained a great attention as a durable photocatalyst for CO2 reduction due to their unique properties. TNTAs have been widely modified with noble metals for increasing their absorption of visible light and limiting their associated rapid electron-hole recombination rate. However, these metals are extremely expensive, which limits their practical applications in the fields of energy and environment. In this study, three noble-metal-free materials of graphitic carbon nitrides, metal-organic framework, and reduced graphene oxide were used for modifying pure TNTAs through a simple drying-deposition method. The modified TNTAs samples were characterized by X-ray diffraction, Fourier transform infrared, field emission scanning electron microscopy and energy-dispersive X-ray spectroscopy analyses for approving successful synthesis of these nanocomposites. Finally, the modified TNTAs nanocomposites were investigated for their ability in converting the CO2 gas to CO under visible light. However, the TNTAs modified with graphitic carbon nitrides displayed the highest CO productions of 27551 mu mol m-2 which represents 16% enhancement compared to that of pure TNTAs (23871 mu mol m-2). The enhanced CO2 photoreduction performance of modified TNTAs is attributed to promoted light absorption, increased surface area, and improved electrical conductivity.