The effect of deposition on electrochemical impedance properties of TiO2/FTO photoanodes

Abstract

The integration of TiO2 layers onto a substrate is challenging and limits the application potential of TiO2. Even though, several studies have been reported to solve this problem by applying various deposition methods, there is still lack of information about how these methods affect the electrochemical and photo-electrochemical properties of resulting electrodes. The TiO2 layers possessing different morphologies, deposited on the conductive FTO glass by means of various different deposition techniques (dip-coating, electrospinning and electrospraying), were used as photoanode (and working electrode) in the three-compartment electrochemical cell. The TiO2 electrodes were calcinated at 450 °C and after that all samples revealed the crystallographic form of anatase. Using these three deposition techniques, three different morphologies were obtained. They consisted of a thin TiO2 nanoparticle layer, TiO2 nanoparticle/nanofiber layer and TiO2 nanorod layer, respectively. The crystallinity and surface properties of the calcinated layers were determined by XRD, Raman spectroscopy, FTIR-ATR and SEM analyses. The electrochemical impedance (EIS) and photo-induced properties of photoanodes were studied by electrochemical measurements. The effects of surface morphology and crystal size of nanostructured layers on electrochemical impedance and photo-electrochemical properties were investigated. The electrodes prepared by dip-coating technique showed the best electrochemical impedance and photo-electrochemical results compared to other two types of electrodes. Dip-coating TiO2 layer possesses the biggest crystal size and lowest charge transfer resistance which result the highest photocurrent density.