Theoretical Investigation of Atomic-Scale Structure and Energetics of the Metal-Electrolyte Interface

Abstract

Understanding the complex and inherently multi-scale interface between a charged electrode surface and a fluid electrolyte would inform design of more efficient and less costly electrochemical energy storage and conversion devices. Joint density-functional theory (JDFT) [1] bridges the relevant length-scales by joining a fully ab initio description of the electrode with a highly efficient, yet atomically detailed classical DFT description [2] of the liquid electrolyte structure, avoiding the costly statistical sampling of the liquid required by molecular dynamics calculations. Leveraging JDFT within our framework to treat charged systems in periodic boundary conditions [3], we then predict the voltage-dependent structure and energetics at the interface between a liquid electrolyte and single-crystalline metallic electrodes. We compare the JDFT-predicted interfacial water structure next to a metallic electrode with results obtained from classical and ab initio molecular dynamics simulations. We go on to elucidate the physical origin of the experimentally measured voltage-dependent differential capacitance of an Ag(111) electrode in aqueous electrolytes, examining the crucial role of ion desolvation and plating onto the electrolyte. Finally, we conclude with an exploration of how the choice of cation and anion in the electrolyte affects the atomically-detailed structure of the metal-liquid interface, yielding fundamental insight into processes in electrodeposition and corrosion. Use of the Center for Nanoscale Materials, an Office of Science user facility, was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. [1] S.A. Petrosyan et al, Phys. Rev. B 75, 205105 (2007) [2] R. Sundararaman, K. Letchworth-Weaver, T. A. Arias, J. Chem. Phys. 140, 144504 (2014) [3] K. Letchworth-Weaver and T. A. Arias, Phys. Rev. B. 86, 075140 (2012)