Light-Driven Chemical Looping for Ammonia Synthesis

Synthetic ammonia has been the primary worldwide source of agricultural fertilizer over the last century and is a promising carbon-free energy carrier for sustainable transportation. Despite its global importance, synthetic ammonia produced with the Haber-Bosch process is extremely energy- and resource-intensive. Here we demonstrate a three-step chemical looping strategy to produce ammonia using only light, natural gas, nitrogen, and water. Titanium nitride nanoparticles were utilized as plasmonic antennas to assist the transformation of magnesium-based nanomaterials through oxide, metallic, and nitride phases under optical illumination. All reactions were performed and monitored in situ using frequency-modulated rotational spectroscopy, which allowed the experiments to take advantage of the rotational spectra's unique sensitivity to isotopic labeling to monitor and verify key reaction intermediates. This validation of a light-driven process for the synthesis of ammonia demonstrates an innovative route toward photosynthetic production of essential chemical commodities.