Enhanced Electrochemical C-N Coupling for Glycine Synthesis via an Active Hydrogen Pump.

Abstract

Direct electrochemical C-N coupling of abundant carbon and nitrogen feedstocks offers a sustainable route to glycine synthesis, yet achieving high efficiency remains challenging. Here, we develop an In-Bi catalyst by incorporating oxophilic indium (In) into a bismuth (Bi) matrix. During the co-reduction of oxalic acid and NO3 -, the In-Bi catalyst delivers an exceptional Faradaic efficiency toward glycine (FEGlycine) of 83.3% with an industrial-level current density of 361.3 mA cm-2, together with a glycine production rate of 4.3 mol h-1 gcat. -1. It outperforms pristine Bi and previously reported state-of-the-art catalysts. Large-scale glycine electrosynthesis is further demonstrated over a 10 cm2 In-Bi electrode, achieving a total current of 1.5 A with FEGlycine of 68.5% and yielding 1.4 g of glycine in 6 h. Mechanistically, oxalic acid and NO3 - first form glyoxylic acid oxime (GAO). Subsequently, In sites act as an "active hydrogen pump" to accelerate H2O dissociation, providing abundant surface-active hydrogen (*H) for efficient GAO hydrogenation to glycine. Meanwhile, the incorporation of In modulates the electronic structure of the Bi matrix, enhancing GAO adsorption and electron transfer. The synergistic regulation of *H supply and electronic structure accelerates the conversion of GAO to glycine, resulting in superior performance of In-Bi.