Urea Electrosynthesis in Microbial Electrolysis Cells Using Low-cost Fe–N–C for Simultaneous N2 and CO2 Reduction

The electrocatalytic synthesis of urea significantly reduces energy consumption compared with that of the traditional Haber–Bosch process. However, few studies regarding suitable electrochemical reactors have been conducted. In this study, we conducted electrolysis in a dual-chamber microbial electrolysis cell with low energy consumption to simultaneously degrade organic matter in wastewater and directly utilize the generated urea in agricultural applications. Detailed optimization and evaluation of low-cost Fe–N–C electrocatalysts prepared via a two-step annealing were conducted. Electroreductions of N2 and CO2 on the bifunctional catalysts generated a favorable amount of urea (0.156 mmol g–1 h–1), and the Faradaic efficiency reached a high level of 2.13%. The gas diffusion electrode significantly enhanced mass transfer between the gaseous reactants and cathode compared with that over the carbon paper electrode. This study provides a promising strategy with low economic and environmental costs for the practical application of urea electrosynthesis in rural areas.