锌-空气电池电解液Zn2+浓度对析氢过程的影响

水溶液体系的二次金属-空气电池通常具有安全环保的特点，但是充电过程中仍然存在析氢副反应的安全隐患。使用线性电势扫描方法、Tafel极化曲线及极限扩散电流密度参数定量分析了二次锌-空气电池体系电解液中Zn²⁺浓度对析氢反应过程的影响。结果表明，随着电解液中Zn²⁺浓度的提高，析氢过电势逐渐增大，Zn²⁺浓度在6 mol·L^-1 KOH溶液中达到0.4 mol·L^-1时，析氢过电势超过2.42 V，析氢过电势比空白溶液提高1.2 V，并且Tafel极化曲线的截距超过1.5 V，析氢电势达到超高过电势范围。此外，由Zn²⁺提供的极限扩散电流密度提高至8.9 A·cm^-2，所对应的过电势提高700 mV。研究结果对于确立二次锌-空气电池极限充电范围提供定量依据，对电池安全平稳运行具有重要价值。

Effects of Zn2+ concentration upon hydrogen evolution reaction for zinc-air battery

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.