Electrochemical Synthesis of Glycine from Oxalic Acid and Nitrate

Abstract

In manufacturing C−N bond‐containing compounds, it is an important challenge to alternate the conventional methodologies that utilize reactive substrates, toxic reagents, and organic solvents. In this study, we developed an electrochemical method to synthesize a C−N bond‐containing molecule avoiding the use of cyanides and amines by harnessing nitrate (NO3−) as a nitrogen source in an aqueous electrolyte. In addition, we utilized oxalic acid as a carbon source, which can be obtained from electrochemical conversion of CO2. Thus, our approach can provide a route for the utilization of anthropogenic CO2 and nitrate wastes, which cause serious environmental problems including global warming and eutrophication. Interestingly, the coreduction of oxalic acid and nitrate generated reactive intermediates, which led to C−N bond formation followed by further reduction to an amino acid, namely, glycine. By carefully controlling this multireduction process with a fabricated Cu–Hg electrode, we demonstrated the efficient production of glycine with a faradaic efficiency (F.E.) of up to 43.1 % at −1.4 V vs. Ag/AgCl (current density≈90 mA cm−2).

Electrocatalytic reduction of nitrate – a step towards a sustainable nitrogen cycle

“…By exploiting the key C–N coupling reaction, they also predicted that ethylamine and propylamine can be generated from CO 2 and nitrate co-reduction catalysed by Cu-based materials. Additionally, Kim et al 319 developed a new electrochemical system of glycine production using CO 2 -derived oxalic acid and nitrate, in which FE reaches 43.1%. Although the current research is still in its infancy, electrochemical synthesis from cheap and abundant inorganic sources such as CO 2 and nitrate is a promising approach to the sustainable production of valuable chemicals.…”

Iron‐Based Nanocatalysts for Electrochemical Nitrate Reduction

“…[48] Combining the NO 3 RR reaction with appealing technologies such as CO 2 reduction to obtain highly selective C-N products via electrochemically coupled reactions may change the way carbon fuels are used today. [148][149][150][151][152] Wu et al accomplished the preparation of methylamines using a molecular cobalt catalyst supported on carbon nanotubes. [153] According to the catalytic 1 h and 5 h test results, Tao et al found that electrochemical CO 2 reduction and NO 3 reduction first proceed independently under the catalysis of oxide-derived Cu nanoparticles, resulting in cascade catalysis and the formation of ethylamine after the formation of key reaction intermediates (Figure 9g-i).…”

Carbon-Nitrogen Bond Formation on Cu Electrodes During Co2 Reduction in No3- Solution

“…Formation of carbon-nitrogen bonds in the form of cyanide was revealed, which was never previously observed at room temperature in aqueous electrolyte. 28 We thus contribute to understanding of electrochemical C-N coupling reactions recently studied in the literature [29][30][31][32] . More importantly, we demonstrate that cyanide likely leads to formation of soluble Cu-C≡N complexes, which suggests a stable process for urea formation based on Cu electrodes might be di cult to achieve.…”