Glycine, an indispensable amino acid essential for diverse biological processes, remains challenging to synthesize directly via electrosynthesis from simple carbon and nitrogen precursors. Herein, we report a highly efficient electrochemical route for glycine production through the reductive coupling of oxalic acid (H2C2O4) with hydroxylamine (NH2OH) or nitrate (NO3 -) over a Mott-Schottky Sn/SnO2 heterojunction catalyst enriched with oxygen vacancies. When employing H2C2O4 and NH2OH as feedstocks, a remarkable Faradaic efficiency (FE) of 91.6% for glycine is achieved at -0.7 V versus RHE, alongside a high yield of 135 mmol gcat. -1 h-1. To the best of our knowledge, this represents one of the best performances ever reported in this system. The catalyst also shows strong substrate versatility, enabling efficient glycine formation when NO3 - (in situ reduced to NH2OH) couples with glyoxylic acid or H2C2O4. Mechanistic studies indicate that the Mott-Schottky heterojunction significantly promotes the co-adsorption of H2C2O4 and NH2OH, while oxygen vacancies facilitate the hydrogenation of oxime intermediates to glycine. This study highlights the profound synergistic interplay between Mott-Schottky heterojunctions and oxygen vacancy defects in precisely modulating active sites and accelerating reaction kinetics, thereby offering a sustainable strategy for the green electrosynthesis of amino acids.
Xu et al. (Sun,) studied this question.