Surface Raman scattering of interfaces at Ag electrodes emersed from dimethylsulfoxide: spectroscopic evidence for an emersion-induced potential shift

Nonaqueous Solvent Adsorption on Transition Metal Surfaces with Density Functional Theory: Interaction of N,N-Dimethylformamide (DMF), Tetrahydrofuran (THF), and Dimethyl Sulfoxide (DMSO) with Ag, Cu, Pt, Rh, and Re Surfaces

“…The relatively low capacitance has previously been hypothesized to contradict the possible reorganization of the DMSO configurations on Au, but here we show that it is possible for the flipping of DMSO between S-up and S-down to be accompanied by only a relatively small change in surface dipole moment. This finding helps to reconcile the experimentally observed low differential capacitance and evidence for field-dependent reorientation/flipping , of DMSO on metals such as Au and Ag. We also found a similar competition between S-down and S-up configurations on Ag(111), Cu(111), and Cu(211), also shown in Figure .…”

“…As mentioned in the introduction, there is experimental evidence for potential-dependent adsorption configuration of DMSO on Ag. , The experimental evidence indicates that at positive potentials, DMSO adsorbed in a configuration with the oxygen atom toward the surface, whereas at negative potentials DMSO adsorbs with the S atom toward the surface. It was hypothesized that this could be explained by the difference in the dipole moment orientation, which would cause a different electrostatic field dependence for the adsorption energy of each configuration. , This leads to the question of how to reconcile this hypothesis with the unusually low differential capacitance of DMSO on Au and similar electrodes, which is accompanied by the contrasting hypothesis that DMSO does not freely reorient in response to the interfacial field. , We investigated this possibility by calculating the field-dependent binding energies for the lowest-energy S-up and S-down configurations on Ag and Cu facets. The results are summarized in Figure .…”

“…As mentioned in the introduction, there is experimental evidence for potential-dependent adsorption configuration of DMSO on Ag. 78,79 The experimental evidence indicates that at positive potentials, DMSO adsorbed in a configuration with the oxygen atom toward the surface, whereas at negative potentials DMSO adsorbs with the S atom toward the surface. It was hypothesized that this could be explained by the difference in the dipole moment orientation, which would cause a different electrostatic field dependence for the adsorption energy of each configuration.…”

“…It was hypothesized that this could be explained by the difference in the dipole moment orientation, which would cause a different electrostatic field dependence for the adsorption energy of each configuration. 78,79 This leads to the question of how to reconcile this hypothesis with the unusually low differential capacitance of DMSO on Au and similar electrodes, which is accompanied by the contrasting hypothesis that DMSO does not freely reorient in response to the interfacial field. 70,74 We investigated this possibility by calculating the field-dependent binding energies for the lowestenergy S-up and S-down configurations on Ag and Cu facets.…”

“…Raman spectroscopy was used to show that DMSO chemisorbs to Au at low electrolyte concentrations, but at higher electrolyte concentrations, it is displaced by adsorption of an electrolyte ion; this is hypothesized to critically affect the formation of an SEI in batteries. On Ag, DMSO has been hypothesized to bind in a potential-dependent way, flipping between binding through O at positive potentials and S at negative potentials, with reorientation of solvent molecules near the PZC. , Interestingly, the differential capacitance of DMSO/Au electrodes , was shown to be significantly smaller than that of solvents with similarly large permanent dipole moments, such as acetonitrile, which would not be expected if the molecule could freely reorient near the interface. Therefore, how to reconcile the experimental evidence for potential-dependent reorientation of DMSO , and its unexpectedly low differential capacitance , at Au or similar electrodes, remains a potentially interesting question.…”