ISSN print edition: 0366-6352
ISSN electronic edition: 1336-9075
Registr. No.: MK SR 9/7
Influence of lead dioxide electrodes morphology on kinetics and current efficiency of oxygen-ozone evolution reactions
Élen C. G. Rufino, Mario H. P. Santana, Luiz A. De Faria, and Leonardo M. Da Silva
Laboratory of Electrochemistry, Institute of Chemistry — UFU, Campus Santa Mônica, Av. João Naves de Ávila 2160, 38400-902 Uberlândia, MG, Brazil
Abstract: Influence of electrode morphology on electrochemical properties of lead dioxide electrodes (β-PbO2) for oxygen-ozone evolution reactions in acid medium was investigated using scanning electronic microscopy (SEM), cyclic
voltammetry (CV), polarization curves (PC), and determination of the current efficiency (Φ). Experimental findings revealed that application of high electrodeposition current densities furnishes more rough β-PbO2 films. Surface characteristics were verified by SEM images and the analysis of interfacial pseudo-capacitances and morphology
factor (φ). Kinetic study of the overall electrode process (O2 + O3) based on the analysis of the Tafel slope revealed that the electrode morphology and electrolyte composition considerably
affect the electrode kinetics. In most cases, the existence of two Tafel slopes distributed in the low and high overpotential
domains was observed. Abnormal Tafel slopes (b ≠ 120 mV) obtained for the primary water discharge step during water electrolysis were interpreted considering the apparent
charge transfer coefficient (α
apa). Optimum conditions for the ozone production were obtained for the less rough β-PbO2 electrode immersed in a sulfuric acid solution (1.0 mol dm−3) containing KPF6 (30 × 10−3 mol dm−3), where the current efficiency of 15 mass % for the ozone production was obtained.
Keywords: lead dioxide electrode - interfacial capacitance - morphology factor - ozone production - electrode kinetics
Full paper is available at www.springerlink.com.
Chemical Papers 64 (6) 749–757 (2010)