Two-dimensional Cu-phenylalanine nanoflakes for efficient and robust CO₂ electroreduction to C₂₊ products

The electrocatalytic reduction of CO₂ to multicarbon (C₂₊) products is of great importance but still faces challenges. The moderate oxidation state of Cu (Cu^δ+) plays a critical role in promoting the C-C coupling, thereby enhancing the Faraday efficiency (FE) for C₂₊ products. However, Cu^δ+ active species are unstable during the reaction. In this work, two-dimensional (2D) Cu-phenylalanine (Cu-phe) nanoflakes by assembling Cu ions and phenylalanine are prepared. X-ray absorption spectroscopy (XAS) is performed to confirm the moderate oxidation state and Cu-O/N coordination of Cu-phe nanoflakes. Owing to the carboxylic ligand and more stable Cu-N coordination, Cu-phe nanoflakes maintain a moderate oxidation state and exhibit high FE for C₂₊ products (88.1% at -0.8 V) in a flow cell, along with excellent stability. This work offers valuable insights for designing stable and efficient catalysts for the electro-conversion of CO₂ into high-value chemical stocks.