Acid adsorption on TiO₂ nanoparticles-an electrochemical properties study

The surface of TiO₂ photoelectrode was treated by dipping in nitric acid and subsequently coating with solar light absorbing dye. The influence of surface-modified photoelectrodes on the performance of dye-sensitized solar cells (DSCs) was investigated. The nitric acid treatment of the photoelectrode increased DSC energy conversion efficiency from 5.4 to 6.2%, which is mainly attributed to the increase in the photocurrent rather than the change in the open circuit voltage. The comparative studies were done using hydrochloric acid treated TiO₂ photoelectrode. This demonstrates that the nitric acid treated photoelectrode retards back electron transfer at the interface with the electrolyte and increases the amount of adsorbed dyes. X-ray photoemission and Fourier transform infrared spectroscopy studies show that the effect of the nitric acid treatment is due to the presence of residual nitrate ions and hydroxyl groups which decrease free surface area and strengthens physical adsorption of dyes.