Characterization of a Marine Wet Solar Cell with Titanium Dioxide and Copper Oxides Electrodes Coated on the Stainless Steel Substrate

Abstract

Introduction Titanium dioxide (TiO2) has been widely studied and applied in solar cells, fuel cells and hydrogen production due to its photocatalytic n-type semiconductor properties. We have been studying photocatalytic properties of titanium dioxide anode which is assembled to a marine wet solar cell along with counter copper oxides cathode. We have studied photocatalytic characteristics of TiO2 electrode and copper oxides electrode, respectively. In this study, TiO2 and copper oxides were coated on the same stainless steel substrate, forming anode and cathode of a solar cell, respectively. The electrochemical and microstructural properties of those electrodes were studied.Preparation of Electrodes and Cell Type 329J4L dual phase (ferritic and austenitic) stainless steel (S.S) was used as the base substrate for coating. The surface of the substrate was polished and cleaned with acetone with ultrasonic cleaner for 10 minutes. After that, the substrate was passivated with 10% vol. nitric acid at 60 ºC for 30 minutes. Half of the surface of the substrate was then deposited with copper film using vacuum deposition method. The Cu-deposited substrate was heat treated to form copper oxides film on the surface. The other half was screen-printed with insulating layer and then heated. On top of the insulating layer, the conducting layer was printed and heated. Titanium dioxide was finally screen printed and heat treated. The finish coating with epoxy resins around the cell was conducted to get prepared for electrochemical measurements and analyses. For comparison and to better understand the photocatalytic effect of each electrode, other types of cells were prepared where only half-cell electrodes are photocatalytic and other parts are conducting layers; TiO2 vs S.S cell and conduction layer vs copper oxides electrode cell.Measurement and Analysis The electrochemical measurement of the cell was performed with a potentiostat under irradiation using a calibrated xenon light source with light intensity of 10.5 mW/cm2 and a wavelength range between 250 nm and 800 nm. The measurement was conducted using artificial seawater as the electrolyte. The microstructure of each electrode was analyzed with optical microscope, scanning electron microscope (SEM) and electron dispersion spectroscopy (EDS).Results and Discussion The power density-cell voltage measurement showed the cell where both electrodes were photocatalytic showed higher photopotential than the cell where only one electrode was photocatalytic. Moreover, cell with both electrodes coated on the same substrate showed higher photopotential than cell with electrodes being separated. This is due to the enhancement of charge flow between electrodes when the electrodes are coated on the same substrate. It is also found out that although titanium dioxide electrode can be heat treated up to 550ºC for better performance in the previous study, the heat treatment temperature for the cell becomes a limit factor since the temperature for copper oxides electrode is the best at 350 ºC to prevent photo corrosion. The different temperatures for heat treatment of the cell were set at 150 ºC, 250 ºC, and 350ºC. The preliminary analysis showed there is a relationship between the heat treatment temperatures and the photocatalytic characteristics of each electrode. The microstructural analysis by SEM of each electrode is underway and will be presented in the ECS conference meeting.