Synthesis of α-Amino Acids via Electrochemical Fixation of CO₂ to Imines Using Different Metal Cathodes

Abstract

The electrochemical fixation of CO2 by imines has recently attracted increased interest as a sustainable strategy for the synthesis of α-amino acids and a green alternative to the traditional Strecker synthesis, which relies on highly toxic precursors. Despite the industrial prospects of the electrochemical approach, the catalyst material effects on the selectivity of the process are still purely understood, hindering rational catalyst design. Herein, we study the electrochemical fixation of CO2 by N-benzylideneaniline using a wide variety of cathode materials, including 10 polycrystalline metals (Ti, Zn, Au, Pd, Pt, Sn, Ag, Ni, Fe, Cu), glassy carbon, and Pd nanoparticles of different shapes. We found that among all studied bulk metals, Ti and Zn show the best results with above 93% faradaic efficiency of α-amino acid, while other materials show from good to low selectivity (12% for Sn). We also demonstrate that especially high current densities and nearly quantitative faradaic efficiency and selectivity of α-amino acids can be achieved by employing nanostructured materials.