One-step Formation of Urea from Carbon Dioxide and Nitrogen Using Water Microdroplets.

Water (H 2 O) microdroplets are sprayed onto a graphite mesh covered with a CuBi 2 O 4 coating using a 1:1 mixture of N 2 and CO 2 as the nebulizing gas. The resulting microdroplets contain urea [CO(NH 2 ) 2 ] as detected by both mass spectrometry and 13 C nuclear magnetic resonance. This gas-liquid-solid heterogeneous catalytic system synthesizes urea in one step on the 0.1 ms time scale. The conversion rate reaches 2.7 mmol g -1 h -1 at 25 °C and 12.3 mmol g -1 h -1 at 65 °C, with no external voltage applied. Water microdroplets serve as the hydrogen source and the electron transfer medium for N 2 and CO 2 in contact with CuBi 2 O 4 . Water-gas and water-solid contact electrification are speculated to drive the reaction process. This strategy couples N 2 fixation and CO 2 utilization in an ecofriendly process to produce urea, converting a greenhouse gas into a value-added product.