Highly Efficient Synthesis of α-Amino Acids via Electrocatalytic C-N Coupling Reaction Over an Atomically Dispersed Iron Loaded Defective TiO2

Abstract

The synthesis of α-amino acids via the electrocatalytic C-N coupling attracted extensive attention owing to the mild reaction conditions, controllable reaction parameters, and atom economy. However, the α-amino acid yield remains unsatisfying. Herein, the efficient electrocatalytic synthesis of α-amino acids is achieved with an atomically dispersed Fe loaded defective TiO₂ monolithic electrocatalyst (_adFe-TiO_x/Ti). The desired electrocatalyst composition for the hydrogenation of oxime is screened. The prepared _adFe-TiO_x/Ti exhibited a high glyoxylic acid conversion of ≈100% and a glycine selectivity of 80.2%. The electrochemical experiments and theoretical calculations demonstrated that atomically dispersed Fe (_adFe) sites and oxygen vacancies (OVs) enhanced the adsorption of glyoxylic acid (GA), glyoxylic oxime (GO), and nitrate (NO₃⁻). _adFe sites further promote the step of H₂NO^* → H₂NOH^* in the conversion of NO₃⁻ to hydroxylamine (NH₂OH) and the step of NH-CH₂-COOH^* → NH₂-CH₂-COOH^* in the reduction of GO to glycine. The coupling pathway and the critical intermediate are revealed by synchrotron radiation Fourier transform infrared (SR-FTIR) spectroscopy and differential electrochemical mass spectrometry (DEMS). Additionally, six other α-amino acids are successfully synthesized by the _adFe-TiO_x/Ti, showcasing its versatility in the electrosynthesis of α-amino acids. This work provides an efficient electrocatalyst for the C-N coupling synthesis of α-amino acids.