Investigation of the electrochemical behaviour of lead dioxide in aqueous sulfuric acid solutions by using the in situ EQCM technique

Abstract

The charge-discharge characteristics and the aging mechanism of PbO 2 layers in contact with sulfuric acid solutions of different concentrations (1.5-5.0 M) were studied by using combined cyclic voltammetry and electrochemical quartz crystal microbalance (EQCM) techniques. For this purpose, thick lead dioxide layers were electrodeposited on gold substrate from aqueous solutions of Pb(NO 3) 2 dissolved in nitric acid. Based on the electrochemical and the mass change responses, it was found that in more concentrated solutions of H 2 SO 4 , the main reduction reaction was the transformation of lead dioxide to lead sulfate. However, in less concentrated sulfuric acid media, the transformation of lead dioxide to lead(II) ion became the main reaction. These Pb 2+ ions transformed into lead sulfate crystals later by a chemical reaction. Because the electrochemical oxidation of lead sulfate is less favourable in sulfuric acid medium of higher concentrations, thus, PbO 2 layers cannot be tested by continuous cyclization, which is necessary to study their aging parameters. Therefore, a delay step before each cyclic voltammogram was applied while the nonconductive lead sulfate dissolves or alternatively, by applying a pre-oxidation step prior to each cyclic voltammetry experiment to produce electrochemically significant amount of lead dioxide which can be reduced during the following negative potential sweep.

Studying the effects of bismuth on the electrochemical properties of lead dioxide layers by using the in situ EQCM technique

“…It is stated that the PbO 2 reduction peak at lower potentials belongs to a more crystalline material and the peak at higher potentials belongs to a more hydrated one. It is also experienced that during the cyclization (aging of the layer), the effective molar mass changes decreased which means that the lead dioxide layer became more and more hydrated which is in good agreement with previous observations [19]. When the solution contained Bi(III), this process was observed much faster which indicates that bismuth accelerates the hydration of lead dioxide.…”

“…The current and the frequency responses during the first three cycles were very similar to previously experienced ones [19]. During the successive cycles, the effective molar mass changes regarding to the transformation of PbO 2 to PbSO 4 were calculated to be ca.…”

“…Porous lead dioxide materials are used in lead-acid batteries [1][2][3][4] as well as in many industrial applications such as wastewater treatment for oxidation of organic compounds [5][6][7][8][9][10][11][12][13]. The electrochemical behavior of pure lead dioxide layers (charge-discharge characteristics, aging processes) has been widely studied previously [14][15][16][17][18][19].…”

“…Based on the Sauerbrey equation [26] and Faraday's law of electrolysis, effective molar mass changes related to the participating species can be calculated. Surprisingly, the EQCM technique has rarely been used for monitoring the changes occurring in the course of charging-discharging of PbO 2 layers [19,27,28].…”

Effect of a Synthesized Pulsed Electrodeposited Ti/PbO2–RuO2 Nanocomposite on Zinc Electrowinning

“…The anodic peak located at 1.9 V corresponds to the Pb(II)/ Pb(IV) oxidation (PbSO 4 to PbO 2 ), and the cathodic peak at 1.1 V represents the Pb(IV)/Pb(II) reduction (PbO 2 to PbSO 4 ). 40 Curves 2−5 in Figure 7 show the PbO 2 composite CV pattern. In this kind of composite anodes, the oxidation peak of the Pb(II)/Pb(IV) disappeared at the OER potential region because RuO 2 nanoparticles catalyze the OER reaction and weaken this peak.…”