采用阳极氧化的方法,通过调节阴、阳两电极间距制备不同壁厚的TiO₂纳米管阵列. 采用脉冲电还原沉积的方法将RGO负载于TiO₂纳米管阵列表面合成了RGO-TiO₂纳米管阵列. 相较于负载在薄壁TiO₂纳米管阵列上的RGO,负载于厚壁TiO₂纳米管阵列上的RGO得以充分还原,覆盖率大幅度提高,并显示出良好的光吸收性质和较低的电荷传输电阻,光电流大幅度增加.

Decorating TiO₂ nanotube arrays with RGO to improve the photocatalytic activity of TiO₂ nanotube arrays has been reported. For the reported RGO-TiO₂ nanotube arrays, TiO₂ nanotube arrays were prepared by anodizing the high-purity Ti foil in an organic electrolyte for multiple-step treatments, while RGO were deposited on TiO₂ nanotube arrays by using cyclic voltammetry or other electrical reduction methods. To enhance the reduction degree and the coverage of RGO on the resultant RGO-TiO₂ nanotube arrays, in this work, the one-step electrochemical anodization in hydrofluoric acid was used to fabricate TiO₂ nanotube arrays with different wall thicknesses by adjusting the distance between the cathode and anode. RGO were loaded on the surface of TiO₂ nanotube arrays by pulse electroreduction deposition. When the distances between the cathode and anode were 4 and 0.5 cm, respectively, the corresponding wall thicknesses of the as-prepared TiO₂ nanotubes were 8 and 14 nm, respectively. Compared with the RGO loaded on the thin-walled TiO₂ nanotube arrays, the RGO loaded on the thick-walled TiO₂ nanotube arrays were fully reduced and the RGO coverage was greatly improved. X-ray photoelectron spectroscopy demonstrated that the reduction degree of RGO loaded on the thick-walled TiO₂ nanotube arrays was higher than that of RGO loaded on the thin-walled TiO₂ nanotube arrays with the decrease of the oxygen content. UV-vis diffuse reflectance spectroscopy showed that the band gap of RGO-TiO₂ nanotube arrays became narrower than that of TiO₂ nanotube arrays due to the loading of RGO. The photocurrent measurements displayed that the photocurrent density of the RGO loaded thick-walled TiO₂ nanotube arrays was significantly increased accordingly, showing good light absorption properties, but also lower charge transfer resistance. The method and results presented in this work would lay a good foundation for the practical photoelectrochemical catalysis application of RGO-TiO₂ nanotube arrays.