Ryan Matthew J, Yang Nan, Kwac Kijeong, Wilhelm Kiera B, Chi Benjamin K, Weix Daniel J, Cho Minhaeng, Zanni Martin T
Department of Chemistry, University of Wisconsin-Madison, Madison, WI 53706.
Center for Molecular Spectroscopy and Dynamics, Institute for Basic Science, Seoul 02841, Republic of Korea.
Proc Natl Acad Sci U S A. 2023 Dec 26;120(52):e2314998120. doi: 10.1073/pnas.2314998120. Epub 2023 Dec 21.
We report the hydrogen-bonding dynamics of water to a nitrile-functionalized and plasmonic electrode surface as a function of applied voltage. The surface-enhanced two-dimensional infrared spectra exhibit hydrogen-bonded and non-hydrogen-bonded nitrile features in similar proportions, plus cross peaks between the two. Isotopic dilution experiments show that the cross peaks arise predominantly from chemical exchange between hydrogen-bonded and non-hydrogen-bonded nitriles. The chemical exchange rate depends upon voltage, with the hydrogen bond of the water to the nitriles breaking 2 to 3 times slower (>63 vs. 25 ps) under a positive as compared to a negative potential. Spectral diffusion created by hydrogen-bond fluctuations occurs on a ~1 ps timescale and is moderately potential-dependent. Timescales from molecular dynamics simulations agree qualitatively with the experiment and show that a negative voltage causes a small net displacement of water away from the surface. These results show that the voltage applied to an electrode can alter the timescales of solvent motion at its interface, which has implications for electrochemically driven reactions.
我们报告了作为外加电压函数的水与腈基功能化等离子体电极表面之间的氢键动力学。表面增强二维红外光谱显示，氢键结合和非氢键结合的腈基特征比例相似，且两者之间存在交叉峰。同位素稀释实验表明，交叉峰主要源于氢键结合和非氢键结合的腈基之间的化学交换。化学交换速率取决于电压，与负电位相比，在正电位下，水与腈基之间的氢键断裂速度慢2至3倍（>63皮秒对25皮秒）。由氢键波动产生的光谱扩散发生在约1皮秒的时间尺度上，并且适度依赖于电位。分子动力学模拟的时间尺度与实验定性一致，表明负电压会导致水从表面产生小的净位移。这些结果表明，施加到电极上的电压可以改变其界面处溶剂运动的时间尺度，这对电化学驱动的反应具有重要意义。
