Copper-Rich Pd_<i>x</i>Cu_1–<i>x</i> Alloy Nanoparticles as Catalyst for Electrochemical Reduction of CO₂

Copper is uniquely able to catalyze the formation of hydrocarbon-derived molecules through the electrochemical carbon dioxide reduction reaction (CO2RR) in aqueous media. Here, we investigate the change of selectivity and/or activity in CO2RR by alloying Cu with palladium by using PdxCu1–x nanoparticles as electrocatalysts. In situ powder X-ray diffraction reveals a much lowered reduction temperature of the Cu-precursor upon alloying and establishes the importance of high heating rates during synthesis to ensure homogeneous Pd alloying into copper-rich PdxCu1–x nanoparticles. Two different synthetic approaches were used to obtain PdxCu1–x nanoparticles with a composition range of x = 0.025–0.20, and the complex nanostructures of the particles were highlighted using four-dimensional Scanning Transmission Electron Microscopy (4D-STEM). The activity and selectivity toward electrochemical CO2RR in 0.1 M KHCO3 were assessed for increasing Pd contents, and a systematic decrease in faradaic efficiency toward hydrocarbon products was found coupled with an increase in faradaic efficiency toward primarily H2. The results do not support PdxCu1–x alloying as a viable method for increasing selectivity toward specific hydrocarbon products in electrochemical CO2RR.