Electrochemical Interfaces

Developing and deploying renewable energy technologies will require the application of knowledge, concepts, and tools from a variety of fields including chemistry, materials science, physics and, in particular, electrochemistry. Electrochemistry is, in the broadest sense, the study of relationships between the transformation of electrical energy in chemical bonds and, in the reverse process, the energy stored in chemical bonds back to electrons that can power electrochemical energy storage and conversion systems. For decades, advances in electrochemistry parallel fundamental understanding of electrochemical interfaces that represents a junction between the electrode material and electrolyte. Central to this presentation will be to introduce – at atomic and molecular levels – electrochemical interfaces in aqueous environment. We first describe the conventionally accepted picture of the double layer, focusing on substrate-adsorbate interactions that involve the sharing of electrons and orbital overlap (covalent bonds) as well as non-covalent electrostatic interactions (e.g., van der Waals forces) between hydrated ions and covalently bonded adsorbents. Examples of covalent-type of interactions will include adsorption of hydrogen, oxygenated species, carbon monoxide, and ions on metal single crystal surfaces in electrolytes with various pH values. Examples of the role of non-covalent interactions will be limited to interaction between hydrated cations and covalently bonded adsorbates. While discussing various types of forces that control interfacial properties we will introduce ex-situ and in-situ experimental/computational probes that have been developed for determining the relationships between the energy of adsorption and relaxation/reconstruction, adsorbate structures and corresponding adsorption isotherms as well as the position of cations in the double layer. We conclude the presentation by announcing the topic of the second lecture: how fundamental understanding of the synergy between covalent and non‑covalent interactions can form the basis for any predictive ability in tailor making active, stable and selective electrochemical interfaces for efficient energy conversion and storage.