Electrochemical behavior of PbO2 nanowires array anodes in a zinc electrowinning solution

Free-standing PbO2 nanowires were prepared by an electrodeposition process onto the titanium foil. The morphology of nanowires was investigated by SEM analyses. The contact angle of the nanowires was compared with that of planar film, which indicated higher hydrophilicity and surface energy of nanowires. Cyclic voltammetric and real-time Fourier transform electrochemical impedance spectroscopy (FTEIS) experiments were employed to study the anodic reaction on the surface. The cyclic voltammetric data showed the overpotential of nanowire array electrode decreased by more than 100mV compared to that of the planar film electrode at an anodic current density of 400A/m2. A large body of impedance data acquired from the two electrodes as a function of scanned potential by running combined staircase cyclic voltammetry and FTEIS experiments led to systematic comparative analysis on the electrode/electrolyte interface. The changes in solution resistances, film resistances and capacitances, double layer capacitances, and polarization resistances observed during oxygen evolution process were compared and explained by corresponding electrochemical reactions. The nanowires of PbO2 showed a large active surface area led to higher capacitance than that of the planar electrode.