Making ammonia from nitrogen and water microdroplets.

Abstract

Water (H₂O) microdroplets are sprayed onto a magnetic iron oxide (Fe₃O₄) and Nafion-coated graphite mesh using compressed N₂ or air as the nebulizing gas. The resulting splash of microdroplets enters a mass spectrometer and is found to contain ammonia (NH₃). This gas-liquid-solid heterogeneous catalytic system synthesizes ammonia in 0.2 ms. The conversion rate reaches 32.9 ± 1.38 nmol s^-1 cm^-2 at room temperature without application of an external electric potential and without irradiation. Water microdroplets are the hydrogen source for N₂ in contact with Fe₃O₄. Hydrazine (H₂NNH₂) is also observed as a by-product and is suspected to be an intermediate in the formation of ammonia. This one-step nitrogen-fixation strategy to produce ammonia is eco-friendly and low cost, which converts widely available starting materials into a value-added product.