Jia Mei, Wang Junyi, Liu Qixiang, Yang Xiaohui, Zhang Chao
Henan Key Laboratory of Biomolecular Recognition and Sensing, Henan Joint International Research Laboratory of Chemo/Biosensing and Early Diagnosis of Major Diseases, College of Chemistry and Chemical Engineering, Shangqiu Normal University, Shangqiu 476000, China.
State Key Laboratory of Physical Chemistry of Solid Surfaces, iChEM, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
J Chem Phys. 2024 Sep 14;161(10). doi: 10.1063/5.0226111.
Water adsorption energy, Eads, is a key physical quantity in sustainable chemical technologies such as (photo)electrocatalytic water splitting, water desalination, and water harvesting. In many of these applications, the electrode surface is operated outside the point (potential) of zero charge, which attracts counter-ions to form the electric double layer and controls the surface properties. Here, by applying density functional theory-based finite-field molecular dynamics simulations, we have studied the effect of water adsorption energy Eads on surface acidity and the Helmholtz capacitance of BiVO4 as an example of metal oxide electrodes with weakly chemisorbed water. This allows us to establish the effect of Eads on the coordination number, the H-bond network, and the orientation of chemisorbed water by comparing an oxide series composed of BiVO4, TiO2, and SnO2. In particular, it is found that a positive correlation exists between the degree of asymmetry ΔCH in the Helmholtz capacitance and the strength of Eads. This correlation is verified and extended further to graphene-like systems with physisorbed water, where the electric double layers (EDLs) are controlled by electronic charge rather than proton charge as in the oxide series. Therefore, this work reveals a general relationship between water adsorption energy Eads and EDLs, which is relevant to both electrochemical reactivity and the electrowetting of aqueous interfaces.
水吸附能Eads是可持续化学技术中的一个关键物理量，这些技术包括（光）电催化水分解、海水淡化和水收集。在许多此类应用中，电极表面在零电荷点（电位）之外运行，这会吸引反离子形成双电层并控制表面性质。在此，通过应用基于密度泛函理论的有限场分子动力学模拟，我们以弱化学吸附水的金属氧化物电极BiVO4为例，研究了水吸附能Eads对表面酸度和亥姆霍兹电容的影响。通过比较由BiVO4、TiO2和SnO2组成的氧化物系列，这使我们能够确定Eads对化学吸附水的配位数、氢键网络和取向的影响。特别地，发现亥姆霍兹电容中的不对称度ΔCH与Eads的强度之间存在正相关。这种相关性在具有物理吸附水的类石墨烯系统中得到验证并进一步扩展，在该系统中，双电层（EDL）由电子电荷而非氧化物系列中的质子电荷控制。因此，这项工作揭示了水吸附能Eads与双电层之间的一般关系，这与电化学反应性和水相界面的电润湿都相关。
