Effect of Supporting Anion for Copper Corrosion in Gas Diffusion Microenvironments

Copper is used in a variety of capacities in the development of renewable energy technologies, including as a catalyst on gas diffusion electrodes in electrochemical devices such as CO2 reduction devices. By gaining a better understanding of Cu corrosion, we can learn more about the durability of devices that utilize copper. However, there are a myriad of factors that influence the kinetics of metal corrosion and deposition, which increases the difficulty to precisely analyze the fundamentals. Factors of concern include adsorbing/desorbing multiple layers of metal, uneven surfaces, defects on the electrode surface, and changes in electrode crystal facets. To mitigate these factors, obtain a more representative picture of Cu corrosion, and investigate the effect of the anions on copper, we created three model systems by employing copper underpotential deposition (UPD) on a single-crystalline Au[111] surface: 1) a phenomenal model system in sulfuric acid; 2) a bridging environment (methane sulfonic acid); and 3) a model microenvironment for gas diffusion (Nafion electrolyte). As a result, a loss in peak sharpness, as well as an increase in the number of peaks that are less resolved were observed in phenomenal and bridging environment, respectively, and a loss in ordered monolayers was seen in model microenvironment. Surprisingly, sulfuric acid and methane sulfonic acid have similar charges passed indicating the same amount of copper is deposited and stripped, whereas much less charge is passed in Nafion, demonstrating that small changes to the supporting anion can have a large effect on Cu UPD structure. As the real world does not exist in a model system, our model microenvironment will provide a better image of Cu corrosion fundamentals in a gas diffusion electrode, which is critical for electrochemical devices application. Figure 1