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 (TiO2-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 center dot 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.