Elevated Pressure Effects on Plasma-Driven Ammonia Synthesis: Insights from Experiments and Kinetic Modeling

Area of Science:

• Plasma Chemistry
• Sustainable Synthesis
• Chemical Engineering

Background:

• Nonthermal plasma (NTP) offers a sustainable route for ammonia synthesis under mild conditions.
• Most research focuses on ambient pressure, leaving benefits of elevated pressure unexplored.

Purpose of the Study:

• To investigate plasma-driven ammonia synthesis under elevated pressure.
• To understand the impact of pressure on yield and reaction mechanisms.

Main Methods:

• Utilized a dielectric barrier discharge reactor up to 3 bar.
• Combined experimental measurements with plasma chemical kinetics modeling.
• Employed in situ optical diagnostics and path flux analysis.

Main Results:

• Elevated pressure suppressed ammonia yield, contrary to thermodynamic expectations.
• Reduced electric field (E/N) decreased with pressure, limiting electron energy for N2 activation.
• Electron-impact dissociation of N2 was identified as the rate-limiting step.

Conclusions:

• Increasing pressure in NTP ammonia synthesis hinders yield by reducing E/N.
• Optimizing plasma conditions, particularly electron-impact N2 dissociation, is key for pressurized synthesis.