ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

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

E-mail: elencris85@yahoo.com.br

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.

DOI: 10.2478/s11696-010-0062-2

Chemical Papers 64 (6) 749–757 (2010)