Atmospheric Pressure Ammonia Synthesis via CO 2 -Coupled Hydrogenation

The Haber–Bosch ammonia synthesis is a cornerstone of global agriculture and the chemical industry, yet it is fundamentally constrained by intrinsic scaling relations, necessitating energy-intensive conditions associated with a significant carbon footprint. Herein, we report a surface redox-mediated chemical looping strategy that utilizes the CO 2 hydrogenation reaction as a chemical trigger to drive ammonia synthesis at atmospheric pressure over a cobalt–molybdenum bimetallic nitride (Co 3 Mo 3 N) nitrogen carrier. Mechanistic investigations reveal that CO 2 induces a dynamic surface oxidation that weakens the intrinsic Mo–N bonds and facilitates the hydrogenation and release of lattice nitrogen as NH 3 . The cycle is closed by a subsequent nitridation step that removes surface oxygen and regenerates the nitride lattice. This redox-mediated mechanism enables an unprecedented NH 3 peak concentration of ∼2.3% and a release rate of 12.4 mmol·g cat –1 ·h –1 at 500 °C under atmospheric pressure, circumventing the thermodynamic limitations that historically hinder low-pressure ammonia synthesis. Our findings demonstrate how dynamic surface engineering can decouple kinetic limitations from thermodynamic constraints, offering a novel paradigm for sustainable nitrogen fixation coupled with carbon utilization.