The Pseudocapacitive Behavior of TiO2 (Anatase) Nanoparticles

Nanocrystalline TiO2 (anatase) was studied over a particle size regime where both capacitive and lithium intercalation processes contribute to the total stored charge. Both the total stored charge (gravimetrically normalized) and the capacitive contribution to the stored charge increase with decreasing particle size. Moreover, by reducing the particle size to the nanoscale regime, faster charge/discharge rates were obtained because the diffusion-controlled lithium-ion intercalation process was replaced by faradaic reactions which occur at the surface of the material. The area normalized capacitance was determined to be 110 – 130 PF/cm2, confirming that the capacitive contribution was pseudocapacitive in nature. The results suggest that the amount of charge stored at the surface of the TiO2 from the pseudocapacitive storage mechanism in nanodimensional materials can be comparable to that obtainable from the intercalation process in bulk materials