Three-dimensional Gd-doped TiO₂ fibrous photoelectrodes for efficient visible light-driven photocatalytic performance

To elucidate the influence of electrode geometry on the photocatalytic performance of TiO₂, herein, we report the synthesis of three-dimensional in situ Gd-doped TiO₂ nanofibers (TiO ₂-NFs) using a simple electrospinning technique. The as-spun pristine TiO₂-NFs show a higher photocatalytic (PC) activity (k = 0.013 m^-1) than the TiO₂ nanoparticles (TiO₂-NPs) (k = 0.006 m^-1) electrode, which could be attributed to the fast electron transport in the 1D NFs. In addition, Gd-doped TiO₂-NFs show nearly five-fold enhancement in the PC degradation rate due to synergistically higher electron transport and production of HO due to the effects of morphology and doping, respectively. In striking contrast, Gd-doping has no influence on the PC activity of TiO₂-NPs due to increased grain boundaries, signifying the vital role of the electrode architecture. The mechanism of Gd doping in pure anatase TiO₂ is investigated using density functional theory (DFT) calculations. The influence of Gd-doping and the electrode architecture on the charge recombination and flat-band potential variation in TiO₂ are discussed elaborately using ultraviolet photoelectron spectroscopy (UPS) and Mott-Schottky analysis, and the implications of these findings for designing doped 3D fibrous photoelectrodes are discussed.