Molecular origin of negative component of Helmholtz capacitance at electrified Pt(111)/water interface.
Molecular origin of negative component of Helmholtz capacitance at electrified Pt(111)/water interface.
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带电 Pt(111)/水界面亥姆霍兹电容负分量的分子起源
DOI：
10.1126/sciadv.abb1219
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发表时间：
2020-10
期刊：
影响因子：
13.6
通讯作者：
Cheng J
中科院分区：
文献类型：
--
作者：
Le JB;Fan QY;Li JQ;Cheng J
水的化学吸附随电极电位的变化而变化，导致双电层的负电容。带电的固体/液体界面是包括电化学和胶体科学在内的众多领域中许多物理化学过程的关键。尽管在这一课题上付出了巨大的努力，但令人意想不到的是，对双电层的分子水平的理解仍然缺乏。尤其令人困惑的是，为什么紧凑的亥姆霍兹层经常在金属电极上显示钟形的差分电容，因为这表明在某些界面水层中存在负电容。在这里，我们报告了最先进的带电Pt(111)/水界面从头算分子动力学模拟，旨在揭示界面水的结构和电容行为。我们的计算再现了钟形微分亥姆霍兹电容，并表明界面水在改变电极电位时遵循弗鲁姆金吸附等温线，导致特殊的负电容响应。我们的工作对界面水的结构和电容提供了有价值的见解，这有助于理解超级电容器中电催化和能量存储的重要过程。
Change in water chemisorption in response to electrode potential leads to negative capacitance in electric double layer. Electrified solid/liquid interfaces are the key to many physicochemical processes in a myriad of areas including electrochemistry and colloid science. With tremendous efforts devoted to this topic, it is unexpected that molecular-level understanding of electric double layers is still lacking. Particularly, it is perplexing why compact Helmholtz layers often show bell-shaped differential capacitances on metal electrodes, as this would suggest a negative capacitance in some layer of interface water. Here, we report state-of-the-art ab initio molecular dynamics simulations of electrified Pt(111)/water interfaces, aiming at unraveling the structure and capacitive behavior of interface water. Our calculation reproduces the bell-shaped differential Helmholtz capacitance and shows that the interface water follows the Frumkin adsorption isotherm when varying the electrode potential, leading to a peculiar negative capacitive response. Our work provides valuable insight into the structure and capacitance of interface water, which can help understand important processes in electrocatalysis and energy storage in supercapacitors.
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