Lv Pengyu, Le The Hai, Eijkel Jan, Van den Berg Albert, Zhang Xuehua, Lohse Detlef
Physics of Fluids group, Faculty of Science and Technology, Max Planck - University of Twente Center for Complex Fluid Dynamics, MESA+ Institute, and J. M. Burgers Centre for Fluid Dynamics, and The BIOS Lab-on-a-Chip group, Faculty of Electrical Engineering, Max Planck - University of Twente Center for Complex Fluid Dynamics, Mathematics and Computer Science, MESA+ Institute, University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands.
Soft Matter & Interfaces Group, School of Engineering, RMIT University, Melbourne VIC 3001, Australia.
J Phys Chem C Nanomater Interfaces. 2017 Sep 28;121(38):20769-20776. doi: 10.1021/acs.jpcc.7b04994. Epub 2017 Sep 5.
Whereas bubble growth out of gas-oversatured solutions has been quite well understood, including the formation and stability of surface nanobubbles, this is not the case for bubbles forming on catalytic surfaces due to , though it has important implications for gas evolution reactions and self-propulsion of micro/nanomotors fueled by bubble release. In this work we have filled this gap by experimentally and theoretically examining the growth and detachment dynamics of oxygen bubbles from hydrogen peroxide decomposition catalyzed by gold. We measured the bubble radius () as a function of time by confocal microscopy and find () ∝ . This diffusive growth behavior demonstrates that the bubbles grow from an oxygen-oversaturated environment. For several consecutive bubbles detaching from the same position in a short period of time, a well-repeated growing behavior is obtained from which we conclude the absence of noticeable depletion effect of oxygen from previous bubbles or increasing oversaturation from the gas production. In contrast, for two bubbles far apart either in space or in time, substantial discrepancies in their growth rates are observed, which we attribute to the variation in the local gas oversaturation. The current results show that the dynamical evolution of bubbles is influenced by comprehensive effects combining chemical catalysis and physical mass transfer. Finally, we find that the size of the bubbles at the moment of detachment is determined by the balance between buoyancy and surface tension and by the detailed geometry at the bubble's contact line.
虽然从气体过饱和溶液中产生气泡的过程已得到很好的理解，包括表面纳米气泡的形成和稳定性，但对于在催化表面上形成的气泡而言情况并非如此，尽管这对气体析出反应以及由气泡释放驱动的微纳马达的自推进具有重要意义。在这项工作中，我们通过实验和理论研究了金催化过氧化氢分解产生的氧气气泡的生长和脱离动力学，填补了这一空白。我们通过共聚焦显微镜测量了气泡半径（）随时间的变化，发现（）∝ 。这种扩散生长行为表明气泡是从氧气过饱和环境中生长的。对于在短时间内从同一位置连续脱离的几个气泡，我们获得了重复良好的生长行为，由此我们得出结论，先前气泡产生的氧气不存在明显的消耗效应，也没有因气体产生导致的过饱和度增加。相比之下，对于在空间或时间上相距较远的两个气泡，观察到它们的生长速率存在显著差异，我们将其归因于局部气体过饱和度的变化。目前的结果表明气泡的动态演化受到化学催化和物理传质综合作用的影响。最后，我们发现气泡脱离瞬间的大小由浮力和表面张力之间的平衡以及气泡接触线处的详细几何形状决定。
