The influence of 3,5-diamino-1,2,4-triazole (DAT) on the electrochemical reduction of carbon dioxide to carbon monoxide on a silver electrode was studied via in situ surface-enhanced Raman spectroscopy (SERS). SERS bands obtained in the absence of DAT indicate potentialdependent adsorption of the CO product to bridge and 3-fold hollow sites. With the addition of DAT, CO adsorption to less-coordinated surface sites was found, including a physisorbed or non-coordinating site that exhibited no significant Stark vibrational shift. Raman peaks associated with adsorbed DAT observed at the same potentials as this species suggest that the ligand promotes weaker CO adsorption, which may be responsible for the high efficiency of the AgDAT catalyst. The observation of potential-dependent methylene stretching vibrations indicates the presence of surface hydrocarbon species while the presence of C-D stretches in deuterated electrolyte confirm that these hydrocarbons are generated as a CO 2 reduction byproduct.1.90 V 9 , indicating a large activation barrier to product formation. This large activation barrier has led to suggestions that other species might be involved in CO 2 reduction in aqueous solution, particularly HCO 3 -, since CO 2 dissolved in water exists in equilibrium with HCO 3 -, which is far For Ar control trials, the pH was reduced through the addition of HClO 4 (Optima, Fischer Scientific) to match. A 1 M KOD deuterated electrolyte was prepared by diluting 40 wt % KOD (98 atom % D, Aldrich) in D 2 O (99.9% D, Cambridge Isotope Laboratories).

We evaluate the effect of chain length for a series of alkyl sulfonic acid additives on Cu electrodeposition by using a combination of electrochemical and Raman spectroscopic methods.

We investigate the mechanism of 3-mercapto-1-propanesulfonate (MPS) acceleration of Cu electrodeposition in the presence of Cl– through comparison with the inactive but related model compounds 1-butanesulfonate and 1-butanethiol (BuSH). In situ shell-isolated nanoparticle-enhanced Raman spectroscopy was used to evaluate these additives as a function of potential. MPS adsorbs to the Cu electrode in the presence of Cl– through the thiol functional group. Density functional theory calculations reveal that the adsorption of thiol has a depolarizing effect on the strength of the interaction between adsorbed Cl– and the electrode surface, the consequences of which are observed spectroscopically. The sulfonate moiety does not interact directly with the electrode. However, cyclic voltammetry used to assess the permeability of adsorbed MPS and BuSH adlayers indicates that the sulfonate group has a more direct role in Cu deposition beyond simple disruption of the surface layer.