Fabrication and corrosion behaviour of platinum-coated titanium electrodes from low temperature molten salt electrolytes

The development of corrosion-resistant platinum coated titanium (Pt/Ti) electrodes for seawater electrolysis in the production of sodium hypochlorite is an important requirement. In this study a new ternary low temperature molten salt (LTMS) LiCl-NaCl-KCl system was chosen as the electrolyte. The direct current method of four Pt electrodes combined with a computer program was employed to measure the relationship between conductivity and temperature of the chosen electrolyte at various PtCl2 concentrations. The pulse current technique was used for fabrication of Pt/Ti electrodes from the chosen LTMS electrolyte at the temperature and PtCl2 concentration where the conductivity of the LTMS system was highest by changing the duty-cycle and plating current density. The morphology and composition of the Pt-coated layer was examined by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). Tafel plots, anodic polarization curves and electrochemical impedance spectroscopy (EIS) were employed to evaluate the corrosion behaviour of the Pt/Ti electrodes. The best quality Pt-coated electrodes were obtained from the pulse plating condition of T-on: T-off = 3: 1 with a current density (i(plat)) of 127.5 mA cm(-2). These had a higher Pt content, nobler corrosion potential (E-corr), lower corrosion current density (i(corr)), lower passive current density (i(pass)) and higher impedance. Furthermore, AFM demonstrated that the best quality Pt/Ti electrode had the lowest surface roughness (R-a) with the. nest grain size.