Ammonia

About: Ammonia is a research topic. Over the lifetime, 16217 publications have been published within this topic receiving 271940 citations. The topic is also known as: NH3 & azane.

Phase of atmospheric secondary organic material affects its reactivity

Abstract: The interconversion of atmospheric organic particles among solid, semisolid, and liquid phases is of keen current scientific interest, especially for particles of secondary organic material (SOM). Herein, the influence of phase on ammonia uptake and subsequent particle-phase reactions was investigated for aerosol particles of adipic acid and α-pinene ozonolysis SOM. The nitrogen content of the particles was monitored by online mass spectrometry for increasing ammonia exposure. Solid and semisolid adipic acid particles were inert to the ammonia uptake for low RH ( 94%) induced a first-order deliquescence phase transition into aqueous particles. Solid particles exposed to supersaturated (RH > 100%) conditions and cycled back to high RH (> 94%), thereby becoming acidic metastable particles, underwent a gradual second-order transition upon ammonia exposure to form aqueous, partially neutralized particles. For α-pinene SOM, ammonia exposure at low RH increased the particle-phase ammonium content by a small amount. Mass spectrometric observations suggest a mechanism of neutralization and co-condensation of acidic gas-phase species, consistent with a highly viscous semisolid upon which adsorption occurs. At high RH the ammonium content increased greatly, indicative of rapid diffusion and absorption in a liquid environment. The mass spectra indicated the production of organonitrogen compounds, possibly by particle-phase reactive chemistry. The present results demonstrate that phase can be a key regulator of the reactivity of atmospheric SOM particles.

Essential role of hydride ion in ruthenium-based ammonia synthesis catalysts

Abstract: The efficient reduction of atmospheric nitrogen to ammonia under low pressure and temperature conditions has been a challenge in meeting the rapidly increasing demand for fertilizers and hydrogen storage. Here, we report that Ca2N:e−, a two-dimensional electride, combined with ruthenium nanoparticles (Ru/Ca2N:e−) exhibits efficient and stable catalytic activity down to 200 °C. This catalytic performance is due to [Ca2N]+·e1−x−Hx− formed by a reversible reaction of an anionic electron with hydrogen (Ca2N:e− + xH ↔ [Ca2N]+·e1−x−Hx−) during ammonia synthesis. The simplest hydride, CaH2, with Ru also exhibits catalytic performance comparable to Ru/Ca2N:e−. The resultant electrons in these hydrides have a low work function of 2.3 eV, which facilitates the cleavage of N2 molecules. The smooth reversible exchangeability between anionic electrons and H− ions in hydrides at low temperatures suppresses hydrogen poisoning of the Ru surfaces. The present work demonstrates the high potential of metal hydrides as efficient promoters for low-temperature ammonia synthesis.