A high throughput optical method for studying compositional effects in electrocatalysts for CO2 reduction

In the problem of electrochemical CO2 reduction, the discovery of earth-abundant, efficient, and selective catalysts is essential to enabling technology that can contribute to a carbon-neutral energy cycle. In this study, we adapt an optical high throughput screening method to study multi-metallic catalysts for CO2 electroreduction. We demonstrate the utility of the method by constructing catalytic activity maps of different alloyed elements and use X-ray scattering analysis by the atomic pair distribution function (PDF) method to gain insight into the structures of the most active compositions. Among combinations of four elements (Au, Ag, Cu, Zn), Au6Ag2Cu2 and Au4Zn3Cu3 were identified as the most active compositions in their respective ternaries. These ternary electrocatalysts were more active than any binary combination, and a ca. 5-fold increase in current density at potentials of -0.4 to -0.8V vs. RHE was obtained for the best ternary catalysts relative to Au prepared by the same method. Tafel plots of electrochemical data for CO2 reduction and hydrogen evolution indicate that the ternary catalysts, despite their higher surface area, are poorer catalysts for the hydrogen evolution reaction than pure Au. This results in high Faradaic efficiency for CO2 reduction to CO. A high-throughput method is presented for the synthesis and testing of alloy electrocatalysts for gas phase CO2 electrolysis. Active ternary alloy catalysts were discovered and their structures characterized by X-ray pair distribution functional analysis.

Automated summary

The study focuses on the discovery of efficient catalysts for electrochemical CO2 reduction, with Au6Ag2Cu2 and Au4Zn3Cu3 identified as the most active compositions among four elements. These ternary electrocatalysts showed significantly higher activity than binary combinations, leading to a 5-fold increase in current density. Additionally, the high Faradaic efficiency for CO2 reduction to CO was observed, despite the ternary catalysts being less effective for hydrogen evolution reaction compared to pure Au.