Effect of the Solvent on the Oxygen Evolution Reaction at the TiO2-Water Interface

We investigate the solvation effect of water on the overpotentials of the oxygen evolution reaction on rutile TiO2 by applying the thermodynamic integration method on atomistic model interfaces with and without the water molecules. We compare the results at the vacuum interface with the commonly used computational hydrogen electrode method, finding overall good agreement. The effect of the solvent is found to be twofold. First, the explicit treatment of the solvent can lead to equilibrium configurations differing from the relaxed structures without solvent. Second, the overpotentials can be affected by up to 0.5 eV. The energetics are subject to electrostatic effects at the interface rather than to modifications in the hydrogen bond network. These results provide a promising perspective for treating the solvent with implicit models.

本研究以金红石相二氧化钛（rutile TiO₂）为对象，通过在含与不含水分子的原子级模型界面（atomistic model interfaces）上应用热力学积分法（thermodynamic integration method），探究水对其表面析氧反应（oxygen evolution reaction, OER）过电位的溶剂化效应（solvation effect）。我们将真空界面下的计算结果与当前常用的计算氢电极法（computational hydrogen electrode method）进行对比，发现二者整体吻合度良好。研究发现溶剂的影响具有双重性：其一，显式溶剂处理可得到与无溶剂弛豫结构（relaxed structures）不同的平衡构型（equilibrium configurations）；其二，溶剂可使过电位产生最高达0.5 eV的改变。体系的能量学特性主要受界面静电效应调控，而非氢键网络（hydrogen bond network）的结构变化。上述研究结果为采用隐式模型（implicit models）处理溶剂体系提供了颇具前景的研究思路。