This study exhibits a design of the discharge product film of a bulk AZ63-Ce-La-Ca (AZ63X) anode for Mg-air battery. An ideal discharge product film for Mg anode is that it could inhibit the anodic hydrogen evolution but does not hinder the transfer of the electrons at the interface. Fortunately, the addition of Ce, La, and Ca into AZ63 alloy achieves this goal. The Mg-air battery with AZ63X anode in 3.5% NaCl has an ultrahigh anodic efficiency of 85.7 ± 1.7% and energy-density of 2431 ± 53 mWh g^-1 with the unique discharge product film, surpassing the values of most reported Mg-air batteries. Furthermore, the alloying elements reduce the anode delamination effect significantly by transforming the block Mg₁₇Al₁₂ phase into the connected Mg₁₇Al₁₂ structure and fine rod Al₂RE and Al₂Ca.

Hydrogen evolution is normally associated with the corrosion or dissolution of Mg alloys in aqueous solutions. This work studied the corrosion behavior of sputtered pure Mg, Mg₈₂Zn₁₈ (at.%), Mg₆₄Zn₃₆ (at.%), and pure Zn in 3.5% NaCl solution. Mg₆₄Zn₃₆ had (ⅰ) an amorphous microstructure with some nano-scale grains, (ⅱ) a corrosion rate substantially lower than that of pure Mg, and (ⅲ) no hydrogen evolution during corrosion or anodic dissolution, because the positive corrosion potential retarded the cathodic hydrogen evolution. This is a new route to prevent hydrogen evolution during Mg corrosion, which has never previously been realized.