Gadea Esteban D, Perez Sirkin Yamila A, Molinero Valeria, Scherlis Damian A
Departamento de Química Inorgánica, Analítica y Química Física/INQUIMAE, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires C1428EHA, Argentina.
Department of Chemistry, The University of Utah, Salt Lake City, UT 84112-0850.
Proc Natl Acad Sci U S A. 2024 Oct 8;121(41):e2406956121. doi: 10.1073/pnas.2406956121. Epub 2024 Oct 2.
Many of the relevant electrochemical processes in the context of catalysis or energy conversion and storage, entail the production of gases. This often implicates the nucleation of bubbles at the interface, with the concomitant blockage of the electroactive area leading to overpotentials and Ohmic drop. Nanoelectrodes have been envisioned as assets to revert this effect, by inhibiting bubble formation. Experiments show, however, that nanobubbles nucleate and attach to nanoscale electrodes, imposing a limit to the current, which turns out to be independent of size and applied potential in a wide range from 3 nm to tenths of microns. Here we investigate the potential-current response for disk electrodes of diameters down to a single-atom, employing molecular simulations including electrochemical generation of gas. Our analysis reveals that nanoelectrodes of 1 nm can offer twice as much current as that delivered by electrodes with areas four orders of magnitude larger at the same bias. This boost in the extracted current is a consequence of the destabilization of the gas phase. The grand potential of surface nanobubbles shows they can not reach a thermodynamically stable state on supports below 2 nm. As a result, the electroactive area becomes accessible to the solution and the current turns out to be sensitive to the electrode radius. In this way, our simulations establish that there is an optimal size for the nanoelectrodes, in between the single-atom and ∼3 nm, that optimizes the gas production.
在催化、能量转换与存储领域，许多相关的电化学过程都会产生气体。这通常意味着在界面处形成气泡核，随之而来的是电活性区域的堵塞，导致过电位和欧姆降。人们设想纳米电极可作为一种手段来扭转这种效应，即抑制气泡形成。然而，实验表明，纳米气泡会在纳米尺度电极上形核并附着，从而对电流形成限制，结果表明，在从3纳米到十分之几微米的宽范围内，电流限制与尺寸和外加电位无关。在此，我们利用包括气体电化学生成的分子模拟，研究直径小至单原子的圆盘电极的电位 - 电流响应。我们的分析表明，在相同偏压下，1纳米的纳米电极提供的电流是面积大四个数量级的电极所提供电流的两倍。提取电流的这种增加是气相不稳定的结果。表面纳米气泡的巨势表明，它们在小于2纳米的载体上无法达到热力学稳定状态。因此，溶液可接触到电活性区域，并且电流对电极半径变得敏感。通过这种方式，我们的模拟确定，在单原子和~3纳米之间存在一个纳米电极的最佳尺寸，可优化气体产生。
