Inner Zn layer and outer glutamic acid film as efficient dual-protective interface of Al anode in Al-air fuel cell

Aqueous alkaline Al-air fuel cells receive more attention in the current green energy market. However, interfacial parasitic corrosion of Al anode is a major challenge. For addressing the above problem and improve the energy conversion efficiency of Al anode, we present a dual-protective interface consisting of an inner Zn layer and an outer glutamic acid film. The results show that the 0.35 M glutamic acid can maximize the inhibition of hydrogen evolution corrosion for Al anode by physical adsorption, resulting in reduction of the number and activity of H2O molecules on the metal anode surface. Moreover, the groups of –NH2 and adjacent CO in glutamic acid molecule are regarded as electrophilic attack regions based on density functional theory, while –COOC– in the side chain tends to receive electrons from metal anode. The harmonious interaction between the above groups and the metal surface ensures the stable adsorption of the organic film. Finally, Al-air fuel cell with the dual-protective interface can output the high capacity of 2110.20 mAh g−1 at 20 mA cm−2, achieving anode efficiency of 70.80%. These findings are available for the corrosion inhibition of metal and the preparation of the high-efficiency Al anode.