Su Hongqian, Sun Jindong, Wang Caizhu, Wang Haofeng
School of Environment and Energy Engineering, Beijing University of Civil Engineering and Architecture, Beijing 100044, China; Building Environment and Energy Power Engineering Experimental Center, Beijing University of Civil Engineering and Architecture, Beijing 100044, China.
School of Environment and Energy Engineering, Beijing University of Civil Engineering and Architecture, Beijing 100044, China; Building Environment and Energy Power Engineering Experimental Center, Beijing University of Civil Engineering and Architecture, Beijing 100044, China.
Ultrason Sonochem. 2024 Aug;108:106968. doi: 10.1016/j.ultsonch.2024.106968. Epub 2024 Jun 22.
Ultrasonic technology has a significant degassing effect and can increase the efficiency of hydrogen production in the proton exchange membrane electrolysis of water. However, further research is needed to understand its influence mechanism on hydrogen bubbles. In this work, a kinetic analysis is performed to investigate the principle of hydrogen production and the kinetic behaviour of hydrogen bubble evolution by applying the ultrasonic amplification technique under static and flow dynamics in the proton exchange membrane electrolysis cell. The evolution of hydrogen bubbles in the static and in the flow dynamic of the aqueous electrolyte solution under ultrasound was characterised by imaging. The results show that the aqueous electrolyte solution in the flow state reduces the size of hydrogen bubbles and increases the detachment speed compared to the static state, which promotes the process of hydrogen bubble evolution, and that the thermal effect of ultrasound on the temperature of the aqueous electrolyte solution in the flow state is very small compared to the static state and can be ignored. Ultrasound has different effects on the different stages of hydrogen bubble evolution. In the nucleation stage, the ultrasonic cavitation effect increases the highly reactive radicals such as •OH, H•, etc., and the mechanical vibration effect of ultrasound increases the nucleation sites, which are denser and more evenly distributed. In the growth phase, the ultrasonic cavitation effect and the mechanical vibration effect promote the breaking of hydrogen bonds of water molecules and improve mass transport, which promotes the growth of hydrogen bubbles, and the fluctuating energy of positive and negative ultrasound promotes the growth of hydrogen bubbles with the vibration speed. In the detachment phase, the radius of the hydrogen bubbles is influenced by the ultrasound. The radius of the hydrogen bubbles changes with the positive and negative ultrasonic pressure, the radius of the hydrogen bubbles at negative ultrasonic pressure increases, the positive ultrasonic pressure decreases, the changing effect of the radius of the hydrogen bubbles favours the detachment of the hydrogen bubbles. In the polymerisation phase, the ultrasound leads to increased polymerisation of the fine bubble streams. Ultrasound contributes to the hydrogen production effect of proton exchange membrane water electrolysis in actual operation.
超声技术具有显著的脱气效果，能够提高质子交换膜水电解制氢的效率。然而，需要进一步研究以了解其对氢气泡的影响机制。在这项工作中，通过在质子交换膜电解槽的静态和流动动力学条件下应用超声强化技术，进行了动力学分析，以研究制氢原理和氢气泡演化的动力学行为。通过成像对超声作用下的水性电解质溶液在静态和流动状态下氢气泡的演化进行了表征。结果表明，与静态相比，流动状态下的水性电解质溶液减小了氢气泡的尺寸并提高了脱离速度，这促进了氢气泡的演化过程，并且与静态相比，超声对流动状态下的水性电解质溶液温度的热效应非常小，可以忽略不计。超声对氢气泡演化的不同阶段有不同影响。在成核阶段，超声空化效应增加了如•OH、H•等高活性自由基，超声的机械振动效应增加了成核位点，这些位点更密集且分布更均匀。在生长阶段，超声空化效应和机械振动效应促进了水分子氢键的断裂并改善了传质，从而促进了氢气泡的生长，正负超声的波动能量随着振动速度促进了氢气泡的生长。在脱离阶段，氢气泡的半径受超声影响。氢气泡的半径随正负超声压力变化，负超声压力下氢气泡半径增大，正超声压力下减小，氢气泡半径的变化效应有利于氢气泡的脱离。在聚合阶段，超声导致细气泡流的聚合增加。在实际运行中，超声有助于质子交换膜水电解的制氢效果。
