Electrochemical Stability of Fluorine Doped Tin Oxide (FTO) Coating at Different pH Conditions

Fluorine doped tin oxide coated glass slides were evaluated for their chemical stability in different pH solutions at room temperature by carrying out potentiodynamic polarization and cyclic voltammetry (CV). The FTO was more stable in 0.1 M HNO 3 and 0.1 M NaCl solutions under both anodic and cathodic polarization conditions. Cathodic polarization in 0.1 M HCl solution resulted in a reduction of SnO 2 to lower valent species. The semiconductivity of FTO, which was n-type at low anodic potentials, was p-type at high anodic potentials possibly due to the formation of a SnO-type surface layer by the removal of lattice oxygen during the oxygen evolution reaction. Cyclic stability of the FTO was evaluated by conducting CV between −2.0 and vbn 2.0 V Ag/AgCl at 1 V/s. Intergranular corrosion was observed and the stability was completely lost after 215 cycles in the 0.1 M HCl solution. The stability of FTO was better in the 0.1 M NaOH solution, wherein the electro-catalytic activity degraded after 500 cycles, the electrical connectivity was maintained even after 4500 cycles.