铂电极与水溶液界面双电层的理论研究

理解铂电极与水溶液界面双电层及其对电催化反应动力学的影响，对发展高效燃料电池及水电解催化剂具有重要意义。经典的Gouy-Chapman-Stern (GCS)理论不能直接用于描述电催化体系的双电层。比如，研究表明铂原子与吸附质之间发生部分电荷转移形成表面电偶极矩，会导致电极表面自由电荷随电极电位呈现非单调现象和负的双电层微分电容；而GCS理论则预测单调表面荷电行为和正的双电层微分电容。本项目以多种铂电极与水溶液界面为研究对象，拟建立一个适用于电催化体系的平均场双电层模型。为此，该模型将引入GCS理论中没有考虑的多吸附质共存及相互作用、吸附质引起的表面电偶极矩、溶剂分子在界面电场下的取向重整、界面附近溶液介电常数的连续变化、离子尺寸效应及离子间静电强相关性等因素，并结合第一性原理计算确定部分参数。在此基础上，揭示表面原子排布、电极电位、溶液特性和反应气氛等参数对双电层结构及特性的影响规律。

Understanding the electrical double layer (EDL) of Pt electrodes in aqueous solution and its effect on electrocatalytic reactions is crucial to the development of more efficient electrocatalysts for fuel cells and electrolyzers. The suitability of the classical Gouy-Chapman-Stern (GCS) model to the EDL of solid electrocatalysts is an open question. For example, recent studies have revealed that the partial charge transfer from metal atoms to adsorbates forms a surface dipole moment, leading to a non-monotonic surface charging relation and negative double-layer differential capacitances of Pt electrodes, which is in sharp contrast with the GCS theory which predicts a monotonic surface charging relation and positive double-layer differential capacitances. Regarding the EDL of various Pt electrodes in aqueous solution, this project strives to develop a mean-field EDL model that is suitable for electrocatalysis systems. To this end, the new model will account for factors that are not described in the GCS model, including the coexistence and interactions of multiple adsorbates, surface dipole moment, ordering reorientation of interfacial water molecules, continuous change in the dielectric constant of solution in the vicinity of the interface, the size effect of and electrostatic correlations between ions. Density functional theory calculations will be employed to determine model parameters. Moreover, the effects of surface atom arrangement, electrode potential, solution properties and gas atmosphere on the EDL will be investigated.