Making ammonia from nitrogen and water microdroplets.

Water (H 2 O) microdroplets are sprayed onto a magnetic iron oxide (Fe 3 O 4 ) and Nafion-coated graphite mesh using compressed N 2 or air as the nebulizing gas. The resulting splash of microdroplets enters a mass spectrometer and is found to contain ammonia (NH 3 ). 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 N 2 in contact with Fe 3 O 4 . Hydrazine (H 2 NNH 2 ) 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.