Morphological effect of composite TiO2 nanorod-TiO2 nanoparticle/PEDOT:PSS electrodes on triiodide reduction

Composite electrodes consisting of TiO2 nanoparticles (NPs)-TiO2 nanorods (NRs) and poly (3,4-ethylene-dioxythiophene)- polystyrene sulfonate (PEDOT:PSS) were prepared on a conductive glass substrate. The presence of TiO2 in the composite structure was proved by X-ray diffraction (XRD) Raman and FTIR-ATR measurements. The surface morphologies of TiO2 NP-PEDOT: PSS, TiO2 NR-PEDOT: PSS and TiO2 NP-TiO2 NR-PEDOT: PSS electrodes were characterized by scanning electron microscopy (SEM). According to the cyclic voltammetry measurement (CV), the electrocatalytic activity of composite electrodes on the reduction of triiodide improved after TiO2 addition compared with pristine PEDOT: PSS and platinum (Pt) electrodes. Electrochemical impedance spectroscopy (EIS) showed that the charge transfer resistance (R-ct) strongly depends on the morphologies (ratio between TiO2 NP and TiO2 NR) of the composite electrodes. It was found that R-ct decreased by increasing the amount of TiO2 nanorod in the whole mixture of TiO2 nanoparticles and PEDOT:PSS.