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

Abstract

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.

The emerging chemistry of self-electrified water interfaces

“…The Zare group recently showed a related reaction that is the formation of urea from droplets in the presence of N 2 and CO 2 . 154…”

Contact-electro-catalysis (CEC)

“…119,120 Moreover, the electric field at contact interfaces can drive the transport and diffusion of charged species, such as electrons. 121,122 Recent studies have suggested that the high-intensity electric field on the surface of water microdroplets is the driving force for electron transfer and subsequent formation of H 2 O 2 in sprayed water. 43,123,124 This electric field also exists at water–oil contact interfaces, and the derived electron transfer can catalyze the generation of reactive oxygen species (ROS) for degrading hexadecane.…”

Pyrogenic Carbon Degradation by Galvanic Coupling with Sprayed Seawater Microdroplets

“…The resultant seawater microdroplets are often referred to as sea spray aerosols with a diameter less than 10 μm, and larger diameter microdroplets that have very short atmospheric lifetimes are also produced . Sprayed water microdroplet interfaces possess a remarkable ability to greatly enhance chemical reactions compared with bulk-phase water, − or to drive spontaneous reactions that are impossible to occur in bulk-phase water. − In particular, the aromatic transformation can be significantly accelerated on water microdroplets. , Therefore, the oceanic wave energy has the potential to transform the dispersed matter in seawater mediated by the interfaces of seawater microdroplets in breaking waves. However, PyC transformation at the interfaces of seawater microdroplets has not been reported so far.…”