Research
Illustration of the electrode/electrolyte interface with a vibrational Stark probe (CO), which senses the interfacial electric field, and a spectroscopically observable cation, which provides information about the distribution of this charged species in the EDL.
Electrochemical Double Layer Effects
听
Electrocatalytic reactions occur at the interface between a solid electrode and a liquid electrolyte, where the electrochemical double layer (EDL) forms. Because the EDL defines the local reaction environment, its properties strongly influence reaction rates and selectivity for processes such as CO鈧� reduction, hydrogen evolution/oxidation, and water oxidation. These properties can be tuned by choosing different supporting鈥慹lectrolyte cations and anions, yet the mechanisms by which ostensibly 鈥渋nert鈥� ions affect electrocatalysis remain unclear. To address this, we use vibrational Stark spectroscopy to probe interfacial electric fields and develop molecular reporters to map ion distributions at the interface. Our goal is to uncover the physical mechanisms by which ions modulate electrocatalysis, enabling the design of electrochemical interfaces optimized for specific reactions.
Further reading:
听
听
Mechanistic Investigations of Photoelectrochemical Water Oxidation
The reduction of renewable, abundant feedstocks to carbon-neutral fuels and other value-added chemicals requires protons and electrons. These must be produced in an oxidation reaction. For large-scale implementation of these reduction processes, it is commonly accepted that the water oxidation reaction is the only practical source of protons and electrons. Efficient water oxidation is therefore of central importance for a sustainable economy. However, the reaction is slow and an economically viable (photo)electrocatalyst has not been identified to date. In this regard, a key challenge is the insufficient understanding of the mechanisms and the kinetic bottlenecks of this reaction. To fill this knowledge gap, we employ vibrational spectroscopy to probe key reaction intermediates. We are particularly interested in how the formation and transformation of these intermediates are affected by factors such as electrolyte pH, photon flux, and electrode potential. These insights will aid in the development of efficient and durable water oxidation catalysts. This project is in collaboration with Prof. Dunwei Wang鈥檚 lab in our department.
Probing Hybrid Electrolyte/Electrode Interfaces
In many electrocatalytic processes, water is not only the solvent but also a reactant, serving as a proton donor or acceptor, or as an oxygen source. Therefore, it is essential to control the reactivity of water at electrocatalytic interfaces. Hybrid electrolytes, which are water/organic solvent mixtures that contain a dissolved salt, can be used to alter the reactivity of water by adjusting the composition of a hybrid electrolyte. However, to take full advantage of this approach, it is essential to understand how the structure and dynamics of the hybrid electrolyte/electrode interface depend on bulk electrolyte composition and electrode potential. This knowledge is largely missing to date. To gain insights into the complex structure and dynamics of the electrocatalytic interface, we take a multi-modal approach: We utilize well-defined vibrational modes of organic solvents (such as the nitrile stretching or the carbonyl stretching vibrations) to probe the local environment of the solvent molecules. We combine this approach with the spectroscopy of the O-H stretch of water, which probes the hydrogen-bonding environment. In doing so, we gain a comprehensive picture of the interfaces formed by hybrid electrolyte and metal electrodes. Our goal is to propose design rules for optimizing hybrid electrolytes for specific reactions. This project is in collaboration with Prof. Alexis Grimaud in our department.