Influence of sorbitol as a green and inexpensive corrosion inhibitor for Al-air batteries: An experimental and theoretical study

The Al-air battery (AAB) is a promising new energy source as an effective supplement to existing energy sources. However, hydrogen evolution reaction (HER) severely limits their application and development. In this paper, an inexpensive green additive, sorbitol, is introduced, and its inhibition effect on HER and its inhibition principle is investigated in experiments, quantum chemistry calculations and molecular dynamics (MD) simulations. The electrochemical experimental results showed that the corrosion inhibition efficiency of sorbitol to pure Al anode significantly increases with increasing concentration of sorbitol, which is up to 54.2 % and 90.16 % with 20 % and 30 % sorbitol, respectively. It is calculated that, in the 4 mol/L NaOH solution with 20 % sorbitol, the capacity density and energy density of AAB significantly increased by 171.4 % and 147.4 %, respectively. This work demonstrates that sorbitol can form a strong hydrogen bond (H-bond) network with water molecules, which can reduce the activity of water and the hydrogen evolution of Al anode. Compared with glycerol and inositol, which possesses the same number of hydroxyl (–OH) groups, sorbitol presents the highest comprehensive HER resistance and battery performance, indicating that molecular backbone length of inhibitor can effectively influence the inhibition properties.