Unraveling the role of polyol additives in mitigating hydrogen evolution and improving anode utilization in magnesium–air batteries

Magnesium-air (Mg-air) batteries are limited by severe Mg self-corrosion and parasitic hydrogen evolution in aqueous electrolytes. Here, D-sorbitol and d-mannitol were investigated as polyol additives for regulating the Mg/electrolyte interface in 3 wt% NaCl. Electrochemical, hydrogen-evolution, surface-characterization, and galvanostatic half-cell measurements showed a concentration-dependent inhibition response, with 5 wt% providing the optimum performance for both additives. D-sorbitol produced the strongest inhibition, decreasing the corrosion current density from 131.0 to 7.46 μA cm⁻², corresponding to an inhibition efficiency of 94.3%, and substantially suppressing hydrogen evolution. Under galvanostatic Mg-anode discharge at 20 mA cm⁻², 5 wt% D-sorbitol increased Mg utilization from 43.5% to 74.4% and specific capacity from 959.4 to 1642.1 mAh g⁻¹. Surface analyses indicate formation of a more persistent and spatially distributed corrosion-product/polyol interphase that restricts electrolyte access while maintaining useful anodic activity. d-mannitol provided weaker long-term inhibition and lower Mg utilization. The results demonstrate that stereochemistry-dependent interfacial organization can influence polyol inhibition and identify D-sorbitol as a promising additive for improving Mg-anode utilization in aqueous electrolytes relevant to Mg-air batteries.