Spectroscopic and Electrochemical Studies of Reduction Reactions for Remediation and Batteries

Abstract

We report on spectroscopic and electrochemical stress studies of reduction reactions relevant for batteries and remediation.Silver is an effective electrocatalyst for the reduction of carbon dioxide to carbon monoxide and other products. Carbon-supported organometallic complexes of Ag with nitrogen-based ligands have been shown to effectively reduce CO2 with performance comparable to that of carbon-supported Ag alone, with increased Faradaic efficiency and less H2 production. The great decrease in the amount of Ag loading required makes these complexes attractive as CO2 reduction catalysts. We employ in situ surface-enhanced Raman spectroscopy (SERS) in order to investigate the mechanism by which CO2 reduction proceeds at silver electrodes in the presence of these nitrogen-based ligands, as well as the structural interactions of the Ag-ligand complex at the electrode interface. We show that an effect of surface decoration is to decrease the affinity of the CO product for the Ag surface, leading to higher rates of CO production.We also use spectroscopic methods to assess the reduction of nitrate and dinitrogen on lithium electrode surfaces. We show that in contrast to the expected formation of lithium nitride, the material on the Li electrode is more complex, yielding an oxynitride species the presence of which is responsible for the partial passivation on the Li surface under these conditions. We contrast the behavior of nitrate on Li with that occurring on Cu under milder conditions.