Efficient Glycine Electrosynthesis via CO₂-Recyclable Hydrogen Donation on Pb/Pb₇Bi₃ Heterointerfaces

Electrochemical synthesis has emerged as a sustainable platform in constructing C─N bonds for amino acid production. Glycine, a particularly valuable target compound, continues to experience escalating global demand, yet achieving simultaneous high efficiency and operational stability remains a persistent challenge. Herein, we demonstrate a CO₂-mediated strategy for glycine electrosynthesis using oxalic acid and N₂/nitrate as feedstocks. By using Pb/Pb₇Bi₃-CO₂ catalytic system, a very high glycine Faradaic efficiency (FE) of 91.8% with durable stability over 120 h could be achieved. Moreover, when using nonthermal plasma-activated N₂ as the nitrogen source, the glycine production rate could maintain at 94.4 µmol h^-1 cm^-2 with N-selectivity as high as 93.2%. Mechanistic investigations combining experiments and theoretical calculations reveal that CO₂ undergoes facile protonation on the Pb/Pb₇Bi₃ heterointerfaces to form ^*OCOH intermediate, which donates hydrogen for the reduction of oxalic acid and nitrate into glyoxylic acid and NH₂OH, respectively, while CO₂ is simultaneously regenerated. Notably, hydrogenation via the ^*OCOH intermediate significantly lowers the energy barriers compared to direct protonation, thereby promoting the subsequent spontaneous C─N bond formation and enabling highly efficient electrosynthesis of glycine.