Bashkatov Aleksandr, Park Sunghak, Demirkır Çayan, Wood Jeffery A, Koper Marc T M, Lohse Detlef, Krug Dominik
Physics of Fluids Group, Max Planck Center for Complex Fluid Dynamics and J. M. Burgers Centre for Fluid Dynamics, University of Twente, Enschede 7500 AE, Netherlands.
Leiden Institute of Chemistry, Leiden University, Leiden 2333 CC, Netherlands.
J Am Chem Soc. 2024 Apr 10;146(14):10177-10186. doi: 10.1021/jacs.4c02018. Epub 2024 Mar 27.
The evolution of electrogenerated gas bubbles during water electrolysis can significantly hamper the overall process efficiency. Promoting the departure of electrochemically generated bubbles during (water) electrolysis is therefore beneficial. For a single bubble, a departure from the electrode surface occurs when buoyancy wins over the downward-acting forces (e.g., contact, Marangoni, and electric forces). In this work, the dynamics of a pair of H bubbles produced during the hydrogen evolution reaction in 0.5 M HSO using a dual platinum microelectrode system is systematically studied by varying the electrode distance and the cathodic potential. By combining high-speed imaging and electrochemical analysis, we demonstrate the importance of bubble-bubble interactions in the departure process. We show that bubble coalescence may lead to substantially earlier bubble departure as compared to buoyancy effects alone, resulting in considerably higher reaction rates at a constant potential. However, due to continued mass input and conservation of momentum, repeated coalescence events with bubbles close to the electrode may drive departed bubbles back to the surface beyond a critical current, which increases with the electrode spacing. The latter leads to the resumption of bubble growth near the electrode surface, followed by buoyancy-driven departure. While less favorable at small electrode spacing, this configuration proves to be very beneficial at larger separations, increasing the mean current up to 2.4 times compared to a single electrode under the conditions explored in this study.
水电解过程中电生成气泡的演变会显著阻碍整体过程效率。因此，促进（水）电解过程中电化学生成气泡的脱离是有益的。对于单个气泡，当浮力超过向下作用的力（如接触力、马兰戈尼力和电力）时，气泡就会从电极表面脱离。在这项工作中，使用双铂微电极系统，通过改变电极间距和阴极电位，系统地研究了在0.5 M硫酸中析氢反应过程中产生的一对氢气泡的动力学。通过结合高速成像和电化学分析，我们证明了气泡-气泡相互作用在脱离过程中的重要性。我们表明，与仅受浮力影响相比，气泡合并可能导致气泡更早脱离，从而在恒定电位下产生相当高的反应速率。然而，由于持续的质量输入和动量守恒，与靠近电极的气泡的重复合并事件可能会使已脱离的气泡在超过临界电流时回到表面，临界电流随电极间距增加。后者导致电极表面附近气泡重新开始生长，随后由浮力驱动脱离。虽然在小电极间距下不太有利，但这种配置在较大间距时被证明非常有益，在本研究探索的条件下，与单个电极相比，平均电流增加了2.4倍。
