Electrocatalytic green ammonia production beyond ambient aqueous nitrogen reduction

Ammonia (NH3), the second highest produced chemical in the world, is dominantly used for fertilizer production to underpin the modern agriculture, and recently attracts increasing interest as an energy-dense, carbon-neutral carrier for renewable energy. The present Haber-Bosch process for NH3 production is energy-, emission-, and capital-intensive. Therefore, recent research efforts have been devoted to developing efficient alternatives with decreased carbon emissions, higher compatibility with renewables, and flexible operation. Electrocatalysis technologies represent a crucial role and great potentials, especially the electrocatalytic nitrogen reduction reaction (NRR). However, the achieved performance is still far from feasibility due to the intrinsic limitations from nitrogen activation and reaction system. In this Review, we first discussed the roadmap towards green NH3, critically assessed the challenges of NRR, and then focused on several emerging strategies beyond conventional catalyst design and engineering under ambient aqueous conditions, including electrolyte effect, operation pressure, Li-mediated reaction, reactor innovation, new N-transformation reactions, and redox-mediated catalysis.