Electrochemical stability and corrosion mechanism of fluorine-doped tin oxide film under cathodic polarization in near neutral electrolyte
Carlos F. Sanz-Navarro, Siaw Foon Lee, Seong Shan Yap, Chen Hon Nee, S. L. Yap
Abstract
Commercial fluorine-doped tin oxide (FTO) coated glass slides were subjected to different cathodic potentials for 15 min in 0.2 M Na2SO4 of pH 6.42 to study their electrochemical stability. Results showed that FTO could maintain its electrochemical stability until -1200 mV. However, when it was cathodically polarized from -1600 mV to more negative potentials, band structure positions started to shift upwards, the electrolyte became more acidic and a porous structure appeared on the FTO surface. At -2000 mV, a layer of metallic Sn was seen deposited on the FTO surface, verified by X-ray diffraction and scanning electron microscopy – energy dispersive X-ray spectroscopy. During the cathodic corrosion in near neutral electrolyte, the reduction of SnO2 to Sn involves water oxidation as well as hydrogen evolution reaction.