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

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 (FE_Glycine) 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 g_cat. ^-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 FE_Glycine 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.