Lake Jack R, Soto Álvaro Moreno, Varanasi Kripa K
Department of Mechanical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
Langmuir. 2022 Mar 15;38(10):3276-3283. doi: 10.1021/acs.langmuir.2c00035. Epub 2022 Mar 1.
The adverse effects of electrochemical bubbles on the performance of gas-evolving electrodes have been extensively studied. However, the ways in which bubbles dynamically alter the electrochemically active surface area during bubble evolution are not well understood. Here, we study hydrogen evolution at industrially relevant current densities by using controlled microtexture to examine this fundamental relationship. Surprisingly, the most densely microtextured electrodes have the lowest performance on an active surface area basis. Using high-speed imaging, we show that the benefits of microtexture to release smaller bubbles more consistently are outweighed by the inactivation induced by bubbles growing within the denser microtexture, causing these performance limitations. Additionally, we show that the area beneath adhered bubbles is electrochemically active, contrary to currently held assumptions. Our study therefore has broad implications for electrode design to avoid ineffective use of precious catalyst materials, which is especially critical for porous electrodes and three-dimensional structures with high specific surface areas.
电化学气泡对析气电极性能的不利影响已得到广泛研究。然而，气泡在演变过程中动态改变电化学活性表面积的方式尚未得到很好的理解。在此，我们通过使用可控微观结构来研究工业相关电流密度下的析氢过程，以考察这一基本关系。令人惊讶的是，在基于活性表面积的情况下，微观结构最密集的电极性能最低。通过高速成像，我们表明，微观结构在更一致地释放较小气泡方面的益处被密集微观结构内生长的气泡所导致的失活所抵消，从而造成了这些性能限制。此外，我们表明，与目前的假设相反，附着气泡下方的区域具有电化学活性。因此，我们的研究对电极设计具有广泛的意义，以避免对珍贵催化剂材料的无效使用，这对于具有高比表面积的多孔电极和三维结构尤为关键。
