Elucidating Charge, Spin, and Solvation Dynamics at Electrochemical Interfaces

Nearly all energy conversion and information processing technologies rely on charge and spin transport in systems that are far from equilibrium. The goal to understand and control these processes motivates the need to develop methods to probe the underlying electron dynamics in functional materials on the relevant scales of time and space. To meet this challenge, we utilize high harmonic generation to produce extreme ultraviolet (XUV) light with femtosecond to attosecond pulse durations. Like X-ray absorption, XUV spectroscopy is element specific, providing chemical details of individual elements in complex materials. To extend this technique to study electron dynamics at surfaces, we have pioneered XUV reflection as a surface sensitive analog of XUV absorption. This method now enables direct observation of interfacial charge and spin transport with surface sensitivity, ultrafast time resolution, and unprecedented chemical specificity. This talk will present recent measurements using linearly and circularly polarized XUV light, which show how spin polarized electron transport increases water splitting efficiency in yttrium iron garnet (Y3Fe5O12) by more than an order of magnitude compared to widely studied hematite (alpha-Fe2O3) through the formation of spin-locked magnon-polarons and how angular momentum exchange between electrons and chiral phonons generates ultrafast spin polarization in chiral semiconductors. Finally, this talk will describe nonlinear vibrational spectroscopy of interfacial electric fields, which mediate charge transfer kinetics during electrochemical catalysis, and show how together these spectroscopic methods provide a detailed understanding of the molecular features of interfaces that govern non-equilibrium reaction dynamics.

Speaker: Robert Baker, Ohio State University