Microstructural Analysis of Metal-Embedded Carbon Molecular Sieve (CMS) Membranes for Sustainable Ammonia Synthesis

Ammonia (NH₃) is a key raw material for fertilizer production, traditionally produced through the energy-intensive Haber-Bosch process, which alone contributes about 1.8% of global CO₂ emissions. In contrast, catalytic membranes have the potential to reduce energy consumption in NH₃ synthesis while maintaining high NH₃ yields. Carbon Molecular Sieve (CMS) membranes, synthesized through high-temperature pyrolysis of fluorinated polyimide precursors, have demonstrated high performance in gas separation due to their bimodal pore size distribution, which offers excellent selectivity for NH₃/H₂ and NH₃/N₂. In this work, their application will be extended to reactive separation by incorporating metals into the membrane structure. The embedded metals (Fe, Ru) will serve as the catalytic sites, while the CMS membrane will facilitate the separation of NH₃ (2.6Å) from similarly sized gases H₂ (2.9Å) and N₂ (3.6Å). A variety of metal incorporation techniques and synthesis conditions will be evaluated, and the resulting materials will be characterized for both their separation and catalytic properties. A novel tool, viz. pressure-decay sorption, is being used to analyze the microstructure of these membranes, focusing on their sorption domains. The tool also probes changes in the microstructure due to high-temperature exposure and environments with 75-100% pure H₂. Additionally, characterization techniques such as X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, X-ray Diffraction (XRD), and BET CO₂ and N₂ physisorption will also be of focus.