In situ synchrotron x-ray diffraction study of Zn/Bi2O3 electrodes prior to and during discharge of Zn-air batteries: Influence on ZnO deposition. (10th August 2018)

• Record Type: Journal Article
• Authors: Santos, Florencio; Abad, José; Vila, María; Castro, Germán R.; Urbina, Antonio; Fernández Romero, Antonio J.
• Is Part Of: Electrochimica acta. Volume 281(2018)
• Page Start: 133
• Page End: 141
• Publication Date: 2018-08-10
• Subjects: In situ measurements -- Zn-Bi2O3 -- Synchrotron XRD -- Zinc/air batteries -- Zinc negative electrode; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2018.05.138
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: Zn-based electrodes containing different amount of Bi2 O3 have been analyzed by synchrotron XRD during the discharging process of a real Zn/air battery. Bi2 O3 is clearly detected for pristine Zn-Bi2 O3 based electrodes. However, immersion of Zn-Bi2 O3 electrodes in 6 M KOH solution before starting the discharge results in the disappearance of Bi2 O3 XRD signature in the pattern and the appearance of new peaks indicating the presence of metallic Bi, regardless of the amount of Bi2 O3 initially included in the Zn-Bi2 O3 electrodes. This behavior together with Open Circuit Voltage measurements points to a spontaneous reduction of Bi 3+ to metallic Bi by the oxidation of Zn to Zn 2+ . Irrespective of the amount of Bi2 O3 present in the negative electrodes, Zn XRD peaks diminish as the discharge proceeds. However, the initial amount of Bi2 O3 clearly affect to ZnO and Bi metal XRD peaks. ZnO peaks are observed only for electrodes without Bi2 O3 or those containing 6% of Bi2 O3 . Conversely, ZnO peaks do not appear in the XRD patterns obtained for higher quantities of Bi2 O3 electrodes. Besides, in this case metallic Bi peaks are observed during all discharging processes, indicating that Bi remained in the electrode. Finally, SEM and EDX studies support these conclusions. Graphical abstract: Image 1 Highlights: Zn-Bi2 O3 electrodes of Zn/air batteries were analysed by in situ Synchrotron XRD. Spontaneous reduction of Bi 3+ to Bi was provided by oxidation of Zn to Zn 2+ in KOH. Small amounts of Bi2 O3 forms metallic Bi together to ZnO flower-like structures. Higher quantity of Bi2 O3 creates massive metallic Bi deposit avoiding ZnO formation.