Heinrich Julian, Ränke Fabian, Schwarzenberger Karin, Yang Xuegeng, Baumann Robert, Marzec Mateusz, Lasagni Andrés Fabián, Eckert Kerstin
Institute of Fluid Dynamics, Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, Dresden 01328, Germany.
Institute of Process Engineering and Environmental Technology, Technische Universität Dresden, Helmholtzstr. 14, 01069 Dresden, Germany.
Langmuir. 2024 Feb 13;40(6):2918-2929. doi: 10.1021/acs.langmuir.3c02863. Epub 2024 Jan 31.
The nucleation of bubbles on solid surfaces is an important phenomenon in nature and technological processes like electrolysis. During proton-exchange membrane electrolysis, the nucleation and separation of the electrically nonconductive oxygen in the anodic cycle plays a crucial role to minimize the overpotential it causes in the system. This increases the efficiency of the process, making renewable energy sources and the "power-to-gas" strategy more viable. A promising approach is to optimize gas separation by surface functionalization in order to apply a more advantageous interface to industrial materials. In this work, the connection between the wettability and bubble nucleation of oxygen is investigated. For tailoring the wettability of Ti64 substrates, the direct laser interference patterning method is applied. A laser source with a wavelength of 1064 nm and a pulse duration of 12 ps is used to generate periodic pillar-like structures with different depths up to ∼5 μm. The resulting surface properties are characterized by water contact angle measurement, scanning electron microscopy, confocal microscopy, and X-ray photon spectroscopy. It was possible to generate structures with a water contact angle ranging from 20° up to nearly superhydrophobic conditions. The different wettabilities are validated based on X-ray photon spectroscopy and the different elemental composition of the samples. The results indicate that the surface character of the substrate adapts depending on the surrounding media and needs more time to reach a steady state for deeper structures. A custom setup is used to expose the functionalized surfaces to oxygen-oversaturated solutions. It is shown that a higher hydrophobicity of the structured surface yields a stronger interaction with the dissolved gas. This significantly enhances the oxygen nucleation up to nearly 350% by generating approximately 20 times more nucleation spots, but also smaller bubble sizes and a reduced detachment rate.
固体表面上气泡的成核是自然界和诸如电解等技术过程中的一种重要现象。在质子交换膜电解过程中，阳极循环中不导电氧气的成核和分离对于最小化其在系统中引起的过电位起着关键作用。这提高了过程的效率，使可再生能源和“电力 - 气体”战略更具可行性。一种有前景的方法是通过表面功能化优化气体分离，以便为工业材料应用更有利的界面。在这项工作中，研究了氧的润湿性与气泡成核之间的联系。为了调整Ti64基板的润湿性，应用了直接激光干涉图案化方法。使用波长为1064 nm、脉冲持续时间为12 ps的激光源来生成深度不同直至约5μm的周期性柱状结构。通过水接触角测量、扫描电子显微镜、共聚焦显微镜和X射线光子能谱对所得表面性质进行表征。能够生成水接触角范围从20°到接近超疏水条件的结构。基于X射线光子能谱和样品的不同元素组成验证了不同的润湿性。结果表明，基板的表面特性根据周围介质而变化，对于更深的结构需要更多时间才能达到稳态。使用定制装置将功能化表面暴露于氧过饱和溶液中。结果表明，结构化表面的更高疏水性会与溶解气体产生更强的相互作用。这通过产生大约20倍更多的成核点显著增强了氧成核，增强幅度高达近350%，而且还减小了气泡尺寸并降低了脱离速率。
