Effect of some metal ions found in recycled battery solutions on the hydrogen evolution reaction potential
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Effect of some metal ions found in recycled battery solutions on the hydrogen evolution reaction potential Renan C. O. Duarte 1 & Eudesio O. Vilar 1 Received: 18 February 2020 / Accepted: 9 October 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Although lead-acid batteries contain about 11 to 30% by weight of electrolyte, the reuse of sulphuric acid solutions raises many questions concerning the advantages of this process, mainly due to the influence of these solutions on performance of batteries. The electrolyte may have critical amounts of dissolved metal ions that can decrease the hydrogen production overvoltage, increasing water loss and decreasing its electrical performance. In the present work, the influence of Cu2+, Mn2+ and Fe3+ ions present in reused electrolytic solutions on the hydrogen evolution potential in the negative electrode was investigated. An assumption of the physicochemical action of these contaminants was investigated by cyclic voltammetry and electrochemical impedance. The results showed that all the metal ions displace the potential of hydrogen evolution to less cathodic values, indicating that these species must have their concentrations minimized to allow acid solution reuse in lead-acid batteries without significant loss of performance. Keywords Solution recycling . Negative electrode . Hydrogen evolution . Water loss
Introduction For decades, lead-acid batteries have been one of the most important energy storage sources due to their wide application in internal combustion engine vehicles, emergency and stationary systems [1–4] and, more recently, in hybrid electric vehicles [5–8]. This device represents a complex electrochemical system of primary and secondary reactions. The discharge reactions are based on the conversion of lead (Pb) and lead dioxide (PbO2) into lead sulphate (PbSO4), while in the charging process, the lead sulphate reverses in the original materials [9, 10]: PbO2 þ H2 SO4 þ 2Hþ þ 2e− ⇄PbSO4 þ 2H2 O
ð1Þ
Pb þ H2 SO4 ⇄PbSO4 þ 2Hþ þ 2e−
ð2Þ
* Eudesio O. Vilar [email protected] Renan C. O. Duarte [email protected] 1
Federal University of Campina Grande, UAEQ/LEEq, Av. Aprígio Veloso, 882 - Universitário, Paraíba 58429-900 Campina Grande, Brazil
In addition to the primary charge-discharge reactions, undesired secondary reactions are also present, especially during overcharging, such as oxygen evolution at the positive electrode and hydrogen evolution at the negative electrode according to the reactions [10]: H2 O⇄1=2O2 þ 2Hþ þ 2e− þ
−
2H þ 2e ⇄2H2
ð3Þ ð4Þ
In valve-regulated lead-acid (VRLA) batteries, the oxygen that is formed at the positive electrode is then almost completely reduced at the negative electrode. This process forms an internal oxygen cycle in the cells [9, 11–13]. In the contrast, the hydrogen produced from the negative plates is particularly undesired, and it usually has to be removed from the battery, since its recombination with the oxygen to form water at the positive plates is ver
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