The charge screening, surface tension, and steric effects of the liquid in electrochemical energy conversion and storage devices can affect electrode surface structure as well as the dominant mechanisms of the interfacial chemical reactions. A comprehensive theoretical description of this solid-liquid interface must capture the relevant physical processes occurring at multiple length and time-scales. The framework of Joint Density-Functional Theory (JDFT) allows simultaneous modeling of the quantum-mechanical properties of a solute system and the collective statistical- mechanical properties of the liquid molecules, avoiding costly thermodynamic sampling, while providing direct access to free energies and atomically-detailed equilibrium liquid structure. Furthermore, continuum liquid theories based on JDFT may be joined with classical and first principles molecular dynamics (MD), enhancing the power of these commonly employed theoretical approaches. Using a synergistic combination of continuum and MD methods, we predict the interfacial structure of metallic and oxide surfaces in liquid, enabling computation of in situ X-ray reflectivity signals from first principles for direct comparison to experimental data and offering insight into structural and electronic properties relevant for catalysis.  We finish by exploring the limitations of current theoretical approaches to predict the structure of the electrochemical double layer, using both experimental X-ray measurements and electrochemical characterization techniques to benchmark our theories.

Integrating first principles theory and X-ray reflectivity measurements to determine solid/liquid interfacial structure

255th National Meeting (2018)

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