Hydrophobic hydration at metal/water interfaces actively contributes to the energetics of electrochemical reactions, e.g. CO2 and N2 reduction, where small hydrophobic molecules are involved. In this work, constant applied potential molecular dynamics is employed to study hydrophobic hydration at a gold/water interface. We propose an adaptation of the Lum–Chandler–Weeks (LCW) theory to describe the free energy of hydrophobic hydration at the interface as a function of solute size and applied voltage. Based on this model we are able to predict the free energy cost of cavity formation at the interface directly from the free energy cost in the bulk plus an interface-dependent correction term. The interfacial water network contributes significantly to the free energy, yielding a preference for outer-sphere adsorption at the gold surface for ideal hydrophobes. We predict an accumulation of small hydrophobic solutes of sizes comparable to CO or N2, while the free energy cost to hydrate larger hydrophobes, above 2.5-Å radius, is shown to be greater at the interface than in the bulk. Interestingly, the transition from the volume dominated to the surface dominated regimes predicted by the LCW theory in the bulk is also found to take place for hydrophobes at the Au/water interface but occurs at smaller cavity radii. By applying the adapted LCW theory to a simple model addition reaction, we illustrate some implications of our findings for electrochemical reactions.

金属/水界面的疏水性水合作用对电化学反应的能量学有积极贡献，例如 C哦2 和 N2减少，其中涉及小的疏水分子。在这项工作中，恒应用电位分子动力学被用来研究金/水界面处的疏水性水合作用。我们建议采用 Lum-Chandler-Weeks (LCW) 理论来描述界面处疏水水合的自由能作为溶质尺寸和施加电压的函数。基于该模型，我们能够直接从体中的自由能成本加上与界面相关的校正项来预测界面处空腔形成的自由能成本。界面水网络对自由能有显着贡献，产生了对理想疏水物的金表面外球吸附的偏好。我们预测大小与 CO 或N2，而水合半径大于 2.5 Å 的较大疏水物的自由能成本在界面处比在主体处更大。有趣的是，还发现从体积主导到表面主导状态的转变也发生在 Au/水界面的疏水物上，但发生在较小的腔半径处。通过将适应的 LCW 理论应用于简单的模型加成反应，我们说明了我们的发现对电化学反应的一些影响。