Owing to the usage of water solution

the secondary metal-air batteries could be excellent for energy storage systems with outstanding advantages in high safety and environmental friendliness. However

the side reaction of hydrogen evolution in the water solution system is the potential hazard for the operation of batteries. In this study

the effects of Zn2+ concentration on hydrogen evolution reaction were investigated with the methods of linear sweep voltammetry

Tafel polarization curves and parameters of limiting diffusion current density for the zinc-air battery. The results showed that the overvoltage of hydrogen evolution reaction reached 2.42 V and the overpotential was 1.2 V higher than that in the blank solution when the concentration of Zn2+ in 6 mol·L-1 KOH solution was 0.4 mol·L-1. The intercept of the Tafel equation was more than 1.5 V

which suggests that the hydrogen evolution reaction for the solution containing 0.4 mol·L-1 Zn2+ reaches the super-overpotential range. The limiting diffusion current density reached 8.9 A·cm-2 and the overpotential was raised by 700 mV. These data are urgently needed for the subsequent operating conditions of the secondary zinc-air batteries and play an important role in the steady and safe operation for the battery system.