The lifetime, coupling, and localization dynamics of electronic states in molecular films near metal electrodes fundamentally determine their propensity to act as precursors or reactants in chemical reactions, crucial for a detailed understanding of charge transport and degradation mechanisms in batteries. In the current study, we investigate the formation dynamics of small polarons and their role as intermediate electronic states in thin films of dimethyl sulfoxide (DMSO) on Cu(111) using time-and angle-resolved two-photon photoemission spectroscopy. Upon photoexcitation, a delocalized DMSO electronic state two monolayers from the Cu surface is initially populated, becoming a small polaron on a 200 fs timescale, consistent with localization due to vibrational dynamics of the DMSO film. The small polaron is a precursor state for an extremely long-lived and weakly-coupled multilayer electronic state, with a lifetime of several seconds, thirteen orders of magnitude longer than the small polaron. Although the small polaron in DMSO has a lifetime of 140 fs, its role as a precursor state for long-lived electronic states could make it an important intermediate in multistep battery reactivity.
To develop a better understanding of electrochemical O2 reduction in nonaqueous solvents, we apply two-photon photoelectron spectroscopy to probe the dynamics of O2 reduction at a DMSO/Cu(111) model battery interface. By analyzing the temporal evolution of the photoemission signal, we observe the formation of O2 – from a trapped electron state at the DMSO/vacuum interface. We find the vertical binding energy of O2 – to be 3.80 ± 0.05 eV, in good agreement with previous results from electrochemical measurements, but with improved accuracy, potentially serving as a basis for future calculations on the kinetics of electron transfer at electrode interfaces. Modeling the O2 diffusion through the DMSO layer enables us to quantify the activation energy of diffusion (31 ± 6 meV), the diffusion constant (1 ± 1 × 10–8 cm2/s), and the reaction quenching distance for electron transfer to O2 in DMSO (12.4 ± 0.4 Å), a critical value for evaluating possible mechanisms for electrochemical side reactions. These results ultimately will inform the development and optimization of metal–air batteries in nonaqueous solvents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.