RESUMEN

Nitrous oxide (N2O), also known as laughing gas, is arguably one of the most detrimental greenhouse gases while concurrently being overlooked by the public. Specifically, N2O is ∼300 times more damaging than its better-known counterpart carbon dioxide (CO2) and has a longer-lived lifetime in the atmosphere than CO2. There exist both natural and anthropogenic sources of N2O, and thus, for a better understanding of sources, capture, and decomposition, it is pivotal to identify N2O within the nitrogen biosphere. This review covers the past and current low-cost N2O gas-sensing technologies, focusing specifically on low-cost metal oxide semiconductors (MOSs), chemiresistive and electrochemical sensors that can provide spatial and temporal monitoring of N2O emissions from various sources. Additionally, compositional modifications to MOsS using metal-organic frameworks (MOFs) are discussed, potentially facilitating new awareness and efforts for increased sensing performance and functionality in N2O detection.

Asunto(s)

Gases de Efecto Invernadero , Óxido Nitroso , Óxido Nitroso/análisis , Dióxido de Carbono/análisis , Gases de Efecto Invernadero/análisis , Nitrógeno

RESUMEN

The induced co-electrodeposition of Ni and Mo is a complex process, where metallic Ni-Mo alloys and Ni-Mo-O composites can originate from the complete and partial reduction of Mo respectively. By adjusting electrolyte compositions and electrodeposition parameters, various metallic, metal/oxide composite, and oxide thin films of Ni-Mo and Ni-Mo-O were electrodeposited from ammonium citrate baths. Ni-ammonia complexes, which play a critical role in promoting the deposition of metallic Ni-Mo alloys, were enhanced at alkaline pH (i.e., 8-10) and lower temperature (i.e., 25-45°C). Moreover, the electrochemical reduction of Ni is under mass transfer limitation, so the deposited Mo content decreased with increasing agitation. On the other hand, higher Mo content can be achieved by relatively higher citrate concentration and larger Mo-to-Ni precursor molar ratio. However, a critical molar ratio of metal precursor resulted in transition from alloy to composite due to Ni inducing the reduction of Mo.

RESUMEN

To understand the effect of complexing agents (i.e., ammonium and citrate) in nickel-molybdenum electrodeposition, calculation of the concentration of various Ni and Mo species as a function of pH and initial concentration of metal ions and complexing agents was performed. In addition, linear sweep voltammetry and Hull cell experiments were systematically investigated to understand the effect of current density and ammonium-to-citrate ratio to film compositions, morphology, and crystallinity. The results indicated that Ni(NH3)3 2+ played a critical role in induced co-deposition mechanism of Ni-Mo alloys, which involved the reduced Ni and absorbed H atoms. Microstructure analysis of deposits indicated that the transition from smooth laminarly grown amorphous Ni-Mo-O composites to columnar and nanocrystalline metallic Ni-Mo alloys with a globular structure as the ammonium-to-citrate molar ratio increases. The highest Mo content of alloys was as high as 19 at%, and up to 70 at% O was present in the composites.