Modulated electrical field as a new pulse method to make TiO2 film for high- performance photo-electrochemical cells and modeling of the deposition process

Abstract

Deposition of charged particles under an electrical field which is expressed as the electrophoretic deposition (EPD) is a fast and simple method of nanoparticle coating. In this research, a comprehensive study was performed to improve the TiO2 film properties by application of modulated electrical fields with different amplitudes, waveforms, and frequencies. The suspension parameters (solvent composition, electrical conductivity, and additive concentration) were also optimized. Final photo-electrodes were characterized with scanning electron microscopy (SEM), atomic force microscopy (AFM), physicochemical, polarization, and photo-electrochemical studies. Based on the results, less particle consumption with better substrate coverage was obtained by applying modulated electrical fields. In the I-V test, the photo-electrodes constructed by applying AC signals with the square waveform at 100 Hz and sinusoidal waveform at 1 kHz showed photo-current density enhancement of about 21 and 18 times (in 1 V vs. Ag/AgCl), respectively, and about 40 % less deposited particle mass in comparison to the photo-electrode prepared in conventional DC electrical field. AC electrical fields could also be used with suspensions containing water as the green solvent. All observations in the EPD processing were successfully interpreted with an electrochemical circuit model that was developed based on the electrochemical impedance spectroscopy (EIS) results and analysis of deposition current.