Stable ammonia synthesis at milder and intermittent conditions on laser-induced graphene supported barium promoted Ruthenium catalyst

Graphitized carbon material derived from laser irradiation of polyimide film (PI) has been utilized for the first time to synthesize barium-promoted ruthenium catalysts for mild ammonia synthesis. The degree of graphitization was modified through thermal treatment in a reactive carbonizing gaseous environment to investigate the influence of the surface properties of laser-induced graphene (LIG) on the activity of Ru-Ba/LIG catalysts. Untreated LIG-based catalysts exhibited superior activity compared to thermally treated LIG catalysts. Particle agglomeration and removal of oxygen functional groups from treated LIGs, confirmed by characterizations, were identified as the reasons for reduced catalytic activity. The LIG-supported Ru catalyst was further tested under various operating conditions, achieving an optimal production rate of 31500 μmol g-1 h-1 for the 5 wt.% Ru-2.5 Ba (Ba/Ru molar ratio) catalyst at 400°C and 1 MPa. The catalyst demonstrated stability over a period of 25 days and maintained performance under intermittent operating and process conditions. Additionally, the catalyst exhibited resistance to hydrogen poisoning. Several characterization techniques were employed to elucidate the surface properties of the LIG-supported catalyst. The graphitic nature of untreated LIG, combined with its oxygen functional groups, fosters a strong metal-support interaction, thereby enhancing the performance of the Ru-based catalyst.