Quantitative Study of Dislocation Density Effects on (100)-Orientated Cu in CO2RR

Abstract

For the electrochemical CO2 reduction reaction, (CO2RR) structural defects have been reported to create key active sites. Previous reports have demonstrated the relationship between structural defects and CO2RR activities. However, an in-depth understanding of the connection between defect structure and selectivity study has proved challenging. In this presentation, we elucidate the relationship between dislocation density, activity, and selectivity on Cu in CO2RR. To accomplish this, we successfully synthesized (100)-oriented Cu samples with dislocation densities varying by a factor of 9, and we quantitatively studied the relationship between dislocation density and CO2RR performance.In this work, we employ (100)-oriented Cu prepared by physical vapor deposition. This approach creates an atomically smooth surface that eliminates the differences in the relative influence based on differences in surface reconstruction and roughness factor. A suite of X-ray-based methods are applied to characterize the defect structure. Here, X-ray diffraction pole figures confirm the good epitaxial growth of Cu (100). X-ray diffraction (XRD) θ/2θ symmetrical scan are applied to facilitate calculation of the dislocation density. Unlike TEM and metallographic etching, this method provides precise structure information over large areas of the Cu catalyst.It is demonstrated that under the potential of -1.04 V vs. RHE, the sample with the largest dislocation density favors HER more. With high dislocation density, HER and C1 products are dominant. The situation changes with the dropping dislocation density, and the best CO2RR performance is achieved at a medium dislocation density changing from 1.668 x 1015 m-2 to 1.106 x 1015 m-2, indicating a favorable catalyst surface for C-C coupled products. Here, a combination of mechanistic study via electrochemical methods and X-ray absorption spectroscopy suggests that a combination of low- and full-coordinated Cu sites is more beneficial for C-C coupling. Figure 1