Warm Plasma Catalysis Enables Rapidly Switchable, Near-Complete Ammonia Cracking for On-Demand Hydrogen Production

Ammonia offers a carbon-free route for hydrogen storage and transport, but decentralized hydrogen supply requires efficient and rapidly responsive cracking technologies. Here, we integrate a warm plasma with Co/MgO–La catalyst to enable ammonia-to-hydrogen conversion without external catalyst heating. At a pure NH3 flow rate of 4 L min–1, the system achieves 99.5% conversion and reaches near-complete conversion within only 6 min after ignition, demonstrating rapid response characteristics, reproducible on–off cycling, and the potential for flexible operation under dynamic electrical inputs. Spatially resolved kinetic analysis and in situ intermediate detection reveal a plasma–thermal–catalytic relay, in which warm plasma generates NHx/H species and localized thermal energy through electron-impact activation and H-radical-mediated thermochemistry, while the downstream catalyst completes the conversion of unreacted NH3 and intermediates. Techno-economic and life-cycle assessments further indicate process-level advantages for this route. This work provides a rapidly switchable platform for distributed and on-demand hydrogen production from ammonia.