An Advanced Alkaline Al-Air Fuel Cell Using l-Ascorbic Acid Interface Layer upon Al Anode via Gradient Anti-corrosion

Al metal is considered as an excellent anode material for metal-air fuel cells thanks to the advantages in terms of capacity and energy density. However, the anodic parasitic corrosion has brought great obstacles to the performance breakthrough of Al-air fuel cells. Herein, we innovatively develop an advanced organic interface layer on an Al anode via gradient anti-corrosion, wherein low-cost, nontoxic, and high-ionized l-ascorbic acid is used to modify two basic research systems, 4 M KOH and 4 M KOH electrolyte containing 0.3 M ZnO. The results show that the relative anti-corrosion efficiency of Al and Zn@Al anodes can be gradually enhanced with the increase of l-ascorbic acid concentration. The optimal modification concentration of l-ascorbic acid is 0.35 M. The capacity and anode utilization of the cell increase to 479.50 mAh/g and 16.09% at 20 mA/cm² after the l-ascorbic acid modification of 4 M KOH, respectively, while an excellent capacity of 2208.39 mAh/g and an anode utilization of 74.09% can be achieved for the cell using an l-ascorbic acid interface layer on a Zn@Al anode at the same current density. The density functional theory reveals that the groups of O-C═C-O and C═O in the layer molecules tend to accept the electrons provided by the Al and Zn@Al surfaces and release more adsorption energy than free H₂O. l-ascorbic acid molecules are adsorbed on the anode surface as a stable interface layer, achieving Al self-corrosion inhibition and promoting the sustainable development of Al-air fuel cells.