Ampere-level ammonia synthesis through grain boundary engineering

Plasma-electrolysis tandem systems can facilitate ammonia (NH₃) production from air and water under ambient conditions via an ‘air → NO_x → NO_x⁻ → NH₃’ pathway. However, NH₃ yields are limited due to a lack of process intensification between plasma generation and electrocatalytic conversion. Here we report a modified cobalt cathode enriched with twin boundaries (TBs) and stacking faults (SFs) (TB/SF-Co) for selective NO₂⁻ reduction. Mechanistic analyses reveal that TB/SF defects upshift the Co d-band centre which strengthens NO₂⁻ adsorption and promotes hydrogenation of intermediates. The material achieves a Faradaic efficiency of 96.7% for NO₂⁻-to-NH₃ conversion at a partial current density of −1.73 A cm⁻². Coupling a cobalt cathode enriched with twin boundaries and stacking faults with a microwave plasma module enables efficient air-to-NH₃ synthesis, achieving an air-to-NO₂⁻ rate of 0.745 mol h⁻¹ and NO₂⁻-to-NH₃ rate of 0.619 mol h⁻¹ with >95% Faradaic efficiency at a total current of more than 101 A in 100 cm² parallel electrolyzers, which rivals or exceeds contemporary benchmarks. (Figure presented.)