电解液中 Cu(111) 晶面电溶解/沉积势垒施加电荷相关性的跨尺度计算
摘要
Behaviors of electrified interface under different applied potentials/charges play the central role in electroplating process and electrochemical corrosion. The mechanism, however, is unclear yet for a surface atom dissolving/depositing from/on an electrode surface under an applied potential. The energy barrier along the reaction path is the key variable. The present work conducts hybrid first-principles/continuum calculations to study the direct and indirect dissolution/ deposition of a Cu atom on perfect/stepped Cu(111) planar electrodes in an electrolyte under different excess charges. Energy profiles present a linear relationship between the energies of the initial/final state and the activation state of different reaction paths under different applied charges, obeying the Brønsted-Evans-Polanyi relation. The activation energy is also a linear or quadratic function of charge density per unit surface area during direct and indirect dissolution/ deposition. These simple relations provide a simple way to deduce the activation energy from the energy of stable states under different charge levels. Analytical formula indicates the occurrence of automatic dissolution from step sites at the applied surface charge density larger than 0.135 \e\/Å<sup>2</sup>. When the applied charge density is between 0.086 \e\/Å<sup>2</sup> and 0.105 \e\/Å<sup>2</sup>, the energy barrier for electrodeposition to the planar surface becomes smaller than zero, while there is a small barrier for surface diffusion, indicating indirect deposition with surface diffusion as the rate determining step. When the applied surface charge density further decreases to lower than 0.086 \e\/Å<sup>2</sup>, the concentration effects of the available deposition sites on steps and planar surface are ignored, becoming mainly the direct deposition because of the energy barrier of surface diffusion.