One-dimensional hierarchical titania for fast reaction kinetics of photoanode materials of dye-sensitized solar cells

To overcome kinetic limitations of nanoparticles and one-dimensional nanostructures, and enhance fast reaction kinetics of photoanode materials for dye-sensitized solar cells, one-dimensional hierarchical titanate was prepared by coating protonated titanate nanoparticles on one-dimensional protonated titanate nanorods. The one-dimensional hierarchical titania was obtained subsequently after calcination at different temperatures, and was characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET). The photoelectrochemical and electrochemical performance of the one-dimensional hierarchical titania was then carried out by photocurrent-voltage curves, electrochemical impedance spectroscopy (EIS), intensity-modulated photovoltage spectroscopy (IMVS) and intensity-modulated photocurrent spectroscopy (IMPS). It is clear that titania nanoparticles grow uniformly on the surface of titania nanorods. The one-dimensional hierarchical titania obtained subsequently can not only provide a matrix similar to the hybrid structure matrix but also avoid forming a large amount of grain boundaries, since the hierarchical structure forms by growth of nanoparticles on nanorods. In particular, the titania with such hierarchical structures after calcination at 600 and 700 degrees C show optimized fast reaction kinetics: low charge-transfer resistance, fast electron transport and long electron lifetime. The knowledge acquired in this work is important for the design of efficient photoanode materials of dye-sensitized solar cells.