O₂ reduction at a DMSO/Cu(111) model battery interface

Abstract

In order to develop a better understanding of electrochemical $\mathrm{O_2}$reduction in non-aqueous solvents, we apply two-photon photoelectronspectroscopy to probe the dynamics of $\mathrm{O_2}$ reduction at aDMSO/Cu(111) model battery interface. By analyzing the temporal evolution ofthe photoemission signal, we observe the formation of $\mathrm{O_2^-}$ from atrapped electron state at the DMSO/vacuum interface. We find the verticalbinding energy of $\mathrm{O_2^-}$ to be 3.80 $\pm$ 0.05 eV, in good agreementwith previous results from electrochemical measurements, but with improvedaccuracy, potentially serving as a basis for future calculations on thekinetics of electron transfer at electrode interfaces. Modelling the$\mathrm{O_2}$ diffusion through the DMSO layer enables us to quantify theactivation energy of diffusion (31 $\pm$ 6 meV), the diffusion constant (1$\pm$ 1$\cdot 10^{-8}$ cm$^2$/s), and the reaction quenching distance forelectron transfer to $\mathrm{O_2}$ in DMSO (12.4 $\pm$ 0.4 \unicode{x212B}),a critical value for evaluating possible mechanisms for electrochemical sidereactions. These results ultimately will inform the development andoptimization of metal-air batteries in non-aqueous solvents.<br