O₂ Reduction at a DMSO/Cu(111) Model Battery Interface

Abstract

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.