Exploring Pd-Ag/Cu electrodes in electrochemical CO2 reduction: Insights into C1, C2, and C3+ chemistry

Abstract

Bimetallic alloy electrodes have been extensively investigated, with multiple metal elements emerging as candidates for developing practical electrodes in electrochemical (EC) CO2 reduction. Understanding C1 chemistry, C–C coupling leading to C2 and C3+ products, and electrode development is crucial for this purpose. In this study, Pd-Ag/Cu electrodes were prepared through the co-sputter deposition of Pd and Ag. These electrodes were tested in EC CO2 reduction to examine the products associated with C1, C2, and C3+, along with exploring their relationships over the Pd-Ag modification. In three different electrolytes—KHCO3, phosphate, and KOH—the presence of overlayer metals enhanced the production of CH4, C2H4, C3+ hydrocarbons, and propanol, while inhibiting ethanol and formate. These outcomes were found to be highly dependent on applied potential and recycling processes. The production mechanisms for CH4 and C2H4 appeared distinct from those of C2H6 and C3+ hydrocarbons, which were elucidated through Fischer-Tropsch (FT) chemistry and Anderson-Schulz-Flory equation analysis. EC CO reduction predominantly led to FT chemistry. These studies offer deeper insights into the interconnected C1, C2, and C3+ chemistry in EC CO2 reduction, contributing to enhanced understanding and potential advancements in alloy electrode development.