Influence of lead dioxide electrodes morphology on kinetics and current efficiency of oxygen-ozone evolution reactions

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.

The Effect of Ni and Sb Oxide Precursors, and of Ni Composition, Synthesis Conditions and Operating Parameters on the Activity, Selectivity and Durability of Sb-Doped SnO2Anodes Modified with Ni

“…Hence current density cannot be the only factor governing current efficiency. This in agreement with Rufino et al 68 and Da Silva et al 69 who reported that ozone current efficiency is affected by temperature, real current density (i.e taking into account electrochemically active surface area), electrode and electrolyte composition.…”

New insights about the electrochemical production of ozone

“…4) with a lower redox potential. Because of that, to promote the formation of the triatomic molecule, strategies such as working with electrodes exhibiting high anodic overpotential for the oxygen evolution reaction [30][31][32][33] or applying rather large current densities should be applied.…”

“…However, the competition between oxygen and ozone generation was found to be a problem and, to overcome it, fluoroanions additions were found to enhance the ozone formation, although this improvement was not found to be totally viable because these species are generally toxic to human beings and harmful to the environment [60]. In addition, the leakage of toxic lead ion to the aqueous phase during the use of lead dioxide coatings was also found to be a significant problem and many efforts were made trying to avoid using different manufacturing procedures and formulations of the coatings [32,39,41,44,[62][63][64]. In addition, the doping of a PbO2-based electrode with certain ions such as, Bi 3 + , Fe 3+ , Со 2+ , and Fwas found to considerably increases its electrocatalytic activity in the formation of hydroxyl radicals, which are the precursors of either О3 synthesis or enhanced the oxidation of substances contaminants.…”

Fabrication and characterisation of a mixed oxide-covered mesh electrode composed of NiCo2O4 and its capability of generating hydroxyl radicals during the oxygen evolution reaction in electrolyte-free water

“…exhibit two linear regions distributed in the low and high values of the scan rate, i.e. two distinct pseudocapacitances can be found for solid electrodes [56,59,66]. This experimental fact can be understood from the theoretical viewpoint by taking into account that the total pseudocapacitive current density (j c,T ) for electrodes containing surface defects is composed of contributions from the 'inner/internal' and 'outer/external' surface regions [59]:…”