Urea Electrosynthesis in Microbial Electrolysis Cells Using Low-cost Fe-N-C for Simultaneous N-2 and CO2 Reduction

The electrocatalytic synthesis of urea significantlyreduces energyconsumption compared with that of the traditional Haber-Boschprocess. However, few studies regarding suitable electrochemical reactorshave been conducted. In this study, we conducted electrolysis in adual-chamber microbial electrolysis cell with low energy consumptionto simultaneously degrade organic matter in wastewater and directlyutilize the generated urea in agricultural applications. Detailedoptimization and evaluation of low-cost Fe-N-C electrocatalystsprepared via a two-step annealing were conducted. Electroreductionsof N-2 and CO2 on the bifunctional catalystsgenerated a favorable amount of urea (0.156 mmol g(-1) h(-1)), and the Faradaic efficiency reached a highlevel of 2.13%. The gas diffusion electrode significantly enhancedmass transfer between the gaseous reactants and cathode compared withthat over the carbon paper electrode. This study provides a promisingstrategy with low economic and environmental costs for the practicalapplication of urea electrosynthesis in rural areas.