Catalyst-free urea synthesis via plasma-driven direct coupling of CO2 and N2 under ambient conditions†

This work demonstrates a new catalyst-free pathway of urea synthesis via direct CO₂/N₂ coupling in spatially separated dual plasma reactors. The design isolates reactive species generation, suppressing oxidative side reactions (e.g., O and OH-induced NH₃ loss) and facilitating C–N coupling. Mechanistic studies indicate CO (from CO₂ dissociation) as the key intermediate, reacting with NH_x to form urea, while minimizing NO_x byproducts. By decoupling plasma zones, the system achieves selective nitrogen fixation under ambient conditions, advancing green urea synthesis without catalysts or extreme energy inputs. This strategy provides mechanistic insights and a scalable platform for sustainable carbon/nitrogen co-utilization.