First-Principles Based Modeling of Structures and Processes at Electrochemical Electrode-Electrolyte Interfaces

In spite of its technological relevance in the energy conversion and storage,
our knowledge about the microscopic structure of electrochemical
electrode-electrolyte interfaces and electrical double layers is still rather
limited. The theoretical description of these interfaces from first
principles is hampered by three facts. i) In electrochemistry, structures and
properties of the electrode-electrolyte interfaces are governed by the
electrode potential which adds considerable complexity to the theoretical
treatment since charged surfaces have to be considered. ii) The theoretical
treatment of processes at solid-liquid interfaces includes a proper
description of the liquid which requires to determine free energies instead of
just total energies. This means that computationally expensive statistical
averages have to be performed. iii) Electronic structure methods based on
density functional theory (DFT) combine numerical efficiency with a
satisfactory accuracy. However, there are severe shortcomings of the DFT
description of liquids, in particular water, using current functionals.

Despite these obstacles, there has already significant progress been made in
the first-principles modeling of electrochemical electrode-electrolyte
interfaces. In this contribution, I will present our attempts to contribute to
this progress by systematically increasing the complexity of the considered
systems [1, 2].  Different approaches to describe aqueous electrolytes at
electrodes using first-principles calculations will be compared: the
electrolyte can be described either as a thermodynamic reservoir or using
implicit of explicit solvent models. The equilibrium coverage of specifically
adsorbed anions such as halides will be addressed which is an integral part
of the realistic modeling of electrochemical double layers. Finally,
first attempts to model the structure of battery electrodes using electronic
structure calculations will be presented.

[1] Axel Gross, Florian Gossenberger, Xiaohang Lin, Maryam Naderian, Sung
Sakong, and Tanglaw Roman, Water structures at metal electrodes studied by
ab initio molecular dynamics simulations, J. Electrochem. Soc. 161, E3015-E3020 (2014).

[2] Nicolas Hoermann, Markus Jaeckle, Florian Gossenberger, Tanglaw Roman,
Katrin Forster-Tonigold, Maryam Naderian, Sung Sakong, and Axel Gross,
Some challenges in the first-principles modeling of structures and processes
in electrochemical energy storage and transfer, J. Power Sources 275, 531-538 (2015).