“Hot Edges” in Inverse Opal Structure Enable Efficient CO2 Electrochemical Reduction and Sensitive in-situ Raman Characterization

Conversion of CO ₂ into fuels and chemicals via electroreduction has attracted significant interest. Via mesostructure design to tune the electric field distribution in the electrode, it is demonstrated that the Cu-In alloy with an inverse opal (CI-1-IO) structure provides efficient electrochemical CO ₂ reduction and allows for sensitive detection of the CO ₂ reduction intermediates via surface-enhanced Raman scattering. The significant enhancement of Raman signals of the intermediates on the CI-1-IO surface can be attributed to electric field enhancement on the "hot edges" of the inverse opal structure. Additionally, a highest CO ₂ reduction faradaic efficiency (FE) of 92% (sum of formate and CO) is achieved at-0.6 V vs. RHE on the CI-1-IO electrode. The diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) results show that the Cu-In alloy with an inverse opal structure has faster adsorption kinetics and higher adsorption capacity for CO ₂. The "hot edges" of the bowl-like structure concentrate electric fields, due to the high curvature, and also concentrate K ⁺ on the active sites, which can lower the energy barrier of the CO ₂ reduction reaction. This research provides new insight into the design of materials for efficient CO ₂ conversion and the detection of intermediates during the CO ₂ reduction process.