Continuous Ammonia Electrosynthesis from Nitrogen and Water in a Monolithic Pd Membrane-Based Flow Cell

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Continuous electrochemical ammonia production is promising for sustainable synthesis.
• Direct water oxidation for proton supply in ammonia synthesis faces challenges with low Faradaic efficiency.
• Existing methods often require molecular hydrogen, adding complexity.

Purpose of the Study:

• To improve Faradaic efficiency in electrochemical ammonia synthesis.
• To enable direct proton supply from water oxidation.
• To establish a viable device configuration for continuous, sustainable ammonia production.

Main Methods:

• Integration of an electrically isolated palladium (Pd) membrane for proton transfer.
• Utilizing Pd as a proton- and electron-conducting membrane in a flow-cell configuration.
• Employing a nonaqueous lithium-mediated nitrogen reduction system.

Main Results:

• Achieved a sustained Faradaic efficiency of 36 ± 4% for ammonia production over 6 hours.
• Operated continuously at a current density of -6 mA cm^-2.
• Confirmed ammonia protons originated from water oxidation via online mass spectrometry.

Conclusions:

• The Pd membrane effectively facilitates proton transport from water oxidation to nitrogen reduction.
• This integrated system offers a practical strategy for sustainable green ammonia synthesis.
• The developed device configuration advances electrochemical lithium-mediated nitrogen reduction technology.