Abstract:

An important challenge related to the photoelectrochemical water splitting is the reduction in the reaction rate caused by the bubble coverage on the electrode surface. In this study, in-situ observation of bubble evolution on the TiO₂ photoanode surface was achieved using an electrochemical system coupled with a high-speed camera system. The effects of reaction temperature on bubble dynamics and mass transfer were systematically explored. It indicated that both the photocurrent and gas evolution efficiency increased as the reaction temperature rise. Furthermore, the bubble growth coefficients during evolution also increased with temperature, consequently enhancing interfacial mass transfer through micro-convection, including single-phase natural convection and micro-convection induced by gas-liquid interface expansion. Although single-phase natural convection played a dominant role in mass transfer, the micro-convection induced by the expansion of gas-liquid interface gradually intensified with rising reaction temperature. Additionally, the bubble detachment size and growth period decreased with increasing reaction temperature. The dynamic model considering the temperature and concentration Marangoni force was established, and the predicted values matched well with the experimental results.

Key words: photoelectrochemical water splitting, bubble, temperature, mass transfer, micro-convection, Marangoni force

摘要：

与光电分解水有关的一个重大难点是由于电极表面的气泡覆盖而引起的阳极反应速率降低。采用耦合电化学测试与高速摄像的实验系统，实现了TiO₂光电极表面气泡行为的原位观察，研究了温度对反应传质以及气泡动力学的影响规律。结果表明，升高反应温度能够显著提高光电流密度与析气效率。在气泡演化过程中，气泡生长系数随着反应温度的升高而增大，涉及单相自然对流与气液界面扩张微对流的边界层内传质作用增强。其中，尽管单相自然对流占传质的主导作用，但随着反应温度的升高气液界面扩张引起的微对流传质作用逐渐增强。此外，气泡脱离尺寸和生长周期随着反应温度的升高而减小，考虑温度与浓度马兰戈尼力的影响建立气泡生长过程的动力学模型，预测值与实验结果接近。

关键词: 光电催化分解水, 气泡, 温度, 传质, 微对流, 马兰戈尼力