Efficient electrosynthesis of alanine from α-keto acids over a self-supported electrocatalyst with superior activity†

Abstract

Currently, electrocatalytic reductive amination of α-keto acids can achieve efficient, sustainable, and environmentally friendly production of amino acids under environmental conditions and developing efficient electrocatalysts is crucial for electrochemical amino acid synthesis. Herein, we have realized the one-step electrosynthesis of alanine using biomass-derived pyruvic acid (PA) and NH₂OH as raw reactants in Na₂SO₄ electrolyte over a self-supported Cu/Ti electrode. The Cu/Ti self-supported electrode exhibited excellent electrocatalytic performance with a high alanine yield of 324 μmol and a favorable Faraday efficiency (FE) of 90.5% at −0.62 V (vs. RHE). In situ X-ray absorption spectroscopy (XAS) analyses indicated electron transfer from the Ti substrate to deposited Cu sites, and the resulting electron-rich Cu sites are favourable for the adsorption of intermediates and inhibit the competitive reaction of the hydrogen evolution reaction (HER), enhancing the alanine selectivity. Further in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy (ATR-SEIRAS) verified the reaction path during the electrochemical amino acid synthesis. Moreover, over 10 kinds of amino acids have been successfully electro-synthesized. Except for alanine, the obtained FEs of over six amino acids are 64.8–74.1%. This strategy presents a sustainable and green way for amino acid synthesis under ambient conditions using renewable energy.