Breaking the Haber-Bosch barrier: New review highlights plasma-assisted ammonia synthesis as a game-changer for green energy storage

Ammonia is far more than just the backbone of the global fertilizer industry; it is a high-density, zero-carbon energy carrier capable of storing more hydrogen than liquid hydrogen itself (17.7 wt.%). However, for over a century, the world has relied on the Haber-Bosch (H-B) process—a massive, energy-intensive method that operates under extreme temperatures and pressures, contributing over 420 million tons of CO₂ emissions annually.

In a comprehensive new review published in the journal ENGINEERING Energy (formerly Frontiers in Energy), researchers from Southeast University explore a promising alternative: dielectric barrier discharge (DBD) plasma-assisted ammonia synthesis. Unlike the traditional H-B process, this emerging technology operates under mild conditions—ambient temperature and atmospheric pressure—by using energetic electrons to "excite" nitrogen and hydrogen molecules into highly reactive radicals.

“The transition from centralized, fossil-fuel-dependent ammonia production to distributed, renewable-energy-driven systems is becoming increasingly obvious,” says researchers, the lead author from Southeast University. “Plasma technology allows us to bypass the massive energy barriers of the nitrogen triple bond (N≡N) without the need for extreme heat, making it perfect for coupling with intermittent wind and solar power.”

The review provides a deep dive into the mechanisms and catalyst systems that make this possible. Key highlights include:

• Overcoming Thermodynamic Limits: Traditional catalysts are limited by "linear scaling relations," where optimization for one reaction step often hinders another. Plasma-assisted reactions disrupt this relationship by providing vibrational or electronic excitation to N₂ molecules, lowering activation energy independently of the surface binding energy.
• Next-Generation Catalyst Systems: The study evaluates various catalyst systems, noting that "metal-carrier" catalysts significantly outperform mono-catalysts. Specifically, mesoporous materials like γ-Al₂O₃ and SBA-15 silica provide a "shielding protection" effect. Their unique pore structures prevent the newly synthesized NH₃ from being decomposed by the plasma discharge, significantly increasing the net yield.
• Economic and Environmental Synergy: By integrating plasma reactors with water electrolysis, "green ammonia" can be produced on-site without carbon emissions. The review provides an economic assessment, suggesting that while energy efficiency is still being optimized, the decentralized nature of plasma systems offers a sustainable loop for agriculture and the burgeoning hydrogen economy.

While challenges remain—such as improving the energy yield for large-scale industrial use—the review concludes that DBD plasma technology offers a versatile and environmentally friendly path forward for global carbon neutrality and efficient electricity-to-fuel storage.

JOURNAL: ENGINEERING Energy (formerly Frontiers in Energy)

DOI: https://doi.org/10.1007/s11708-024-0949-1

Article Link: https://link.springer.com/article/10.1007/s11708-024-0949-1

Cite this article: GONG F, JING Y, XIAO R. Plasma-assisted ammonia synthesis under mild conditions for hydrogen and electricity storage: Mechanisms, pathways, and application prospects. Frontiers in Energy, 2024, 18(4): 418–435.