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
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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:
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Mechanistic Investigations of Photoelectrochemical Processes
Understanding catalytic mechanisms requires identifying the structures
and kinetics of short鈥憀ived reaction intermediates, yet these species are often difficult to observe because they possess weak oscillator strengths and/or low populations. Our work addresses this challenge by advancing vibrational spectroscopic methods that enhance interfacial sensitivity and enable time鈥憆esolvedmeasurements under operando conditions.
We combine surface鈥慹nhanced infrared absorption spectroscopy (SEIRAS) with phase鈥憇ensitive detection (PSD). PSD-SEIRAS can resolve subtle dynamic changes in intermediate populations during electrochemical cycling. We are particularly interested the (photo)electrocatalytic oxidation of water, a reaction that supplies the protons and electrons required for converting abundant feedstocks into carbon鈥憂eutral fuels. Although essential for sustainable energy technologies, water oxidation remains slow and mechanistically not sufficiently understood. By probing how key intermediates form, transform, and respond to variables such as pH, photon flux, and electrode potential, we aim to identify the kinetic bottlenecks that limit catalytic efficiency. These insights will guide the design of more active anddurable (photo)catalysts for large鈥憇cale energy conversion.听This project is in collaboration with Prof. Dunwei Wang鈥檚 lab in our department.
Further Reading:
Illustration of how the combination of phase sensitive detection (PSD) and surface-enhanced indrared absorption spectroscopy (SEIRAS) can be used to detect reaction intermediate. The system is periodically excited by varying the electrode potential. The time dependent response of the system is monitored, and noise is removed by transforming the data into the phase domain.
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.