Effect of Sn and Zn alloying with Al on its electrochemical performance in an alkaline media containing CO2 for Al-air batteries application

Aluminum alloyed with other metals, such as Sn and Zn, was synthesized via fusion to trace the impact of alloying elements on the electrochemical characteristics of Al anodes. The corrosion inhibition and electrochemical tests were performed in a 5 M KOH medium in the absence and presence of CO₂ for the Al–Sn, and Al–Zn anodes and compared to the commercial aluminum. Tafel polarization exhibited that the anodic and cathodic branches display lower current densities than Al metal in pure KOH. The steady state of the open circuit voltage (E_corr.) for the studied alloys was shifted to a more negative magnitude than for Al. The corrosion current is sharply decreased, and potential is significantly shifted to less negative values in the presence of CO₂. This is due to forming of a protective layer from the carbonate of Al, Sn, and Zn on the surface. Amazing results were obtained and discussed in the case of CO₂. Electrochemical impedance spectroscopy (EIS) results exhibited that charge transfer resistance (R_ct) values rise with alloying elements. The data of Tafel plots are consistent with those of EIS. The alloying of Al with Sn and Zn elements significantly affects capacitance, hydrogen evolution process suppression, and charge-discharge efficiency. This reveals that the highest potential value in the presence of CO₂ in the charging process is obtained for Al–Zn alloy, while the most negative potential is obtained for Al in the discharging process with CO₂. Moreover, the discharge time is higher in the alloys than in commercial Al in the absence and more in the presence of CO₂. The produced alloys are thought to provide good anodes for long-life rechargeable batteries.