Air degradation
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Summary
6 papers analyzed
These studies suggest that air degradation involves chemical reactions with pollutants, the role of non-thermal plasma air purifiers, and challenges in accurately measuring pollutant levels.
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Air Degradation: Insights from Recent Research
Degradation of Volatile Organic Compounds (VOCs) in Air Purifiers
Non-Thermal Plasma Air Purifiers
Non-thermal plasma air purifiers have been studied for their ability to degrade volatile organic compounds (VOCs) in indoor air. Research has shown that these systems can degrade compounds such as cyclohexene, benzene, toluene, ethylbenzene, and xylene isomers, albeit with varying efficiencies. For instance, degradation efficiencies were found to be 11% for cyclohexene, less than 2% for benzene, 11% for toluene, 3% for ethylbenzene, and around 1-3% for xylene isomers. The degradation process primarily involves reactions with ozone and hydroxyl (OH) radicals, leading to the formation of various oxidized species such as alcohols, aldehydes, ketones, and epoxides.
Polycyclic Aromatic Hydrocarbons (PAHs) in Urban Air
Seasonal and Decadal Trends
Polycyclic aromatic hydrocarbons (PAHs) are significant pollutants in urban air, with their concentrations showing distinct seasonal and decadal trends. Studies conducted in Munich, Germany, revealed that PAH concentrations are higher in winter due to increased heating activities and lower in summer. Over the decades, there has been a notable decrease in PAH levels, attributed to improved emission controls and reduced usage of PAH-emitting sources.
Chemical Degradation and Sampling Artifacts
PAHs undergo chemical degradation in the atmosphere, primarily through reactions with atmospheric oxidants like ozone. This degradation can lead to the formation of oxygenated and nitrated derivatives, which are often more toxic than the parent compounds. Additionally, sampling artifacts during air monitoring can result in significant underestimation of PAH concentrations, with degradation occurring on the filters used for sampling.
Degradation of Organic Solar Cells Due to Air Exposure
Impact of Air Exposure
Organic solar cells are susceptible to degradation when exposed to air, particularly due to the hygroscopic nature of the PEDOT:PSS layer used in these devices. This layer adsorbs water, leading to increased resistance at the interface and reduced photovoltaic performance. The degradation is primarily light-independent and is exacerbated by the presence of moisture in the air.
Photochemical Air Pollution
Mathematical Modeling
Photochemical air pollution, caused by the presence of photochemical oxidants, poses a significant environmental challenge in densely populated areas. Mathematical models have been developed to describe the production and transport of these oxidants within urban airsheds, providing a tool for evaluating the impact of various control measures on air quality.
Degradation of Semivolatile Organic Compounds (SVOCs) During Air Sampling
Within-Sampler Degradation
Semivolatile organic compounds (SVOCs) can degrade within air samplers during both active and passive air sampling, leading to underestimation of their ambient concentrations. Studies have shown that particle-bound PAHs, in particular, are prone to degradation, with concentrations up to twice as high in samplers equipped with ozone denuders compared to those without. This degradation is influenced by the presence of reactive trace gases like ozone and NOx.
Degradation of Sodium-Ion Battery Cathodes
Air-Exposure Degradation Chemistry
Layered sodium transition-metal oxide cathodes in sodium-ion batteries degrade upon exposure to air, forming compounds such as NaOH, Na2CO3, and Na2CO3·H2O. This degradation involves the extraction of Na+ ions and the dissolution of nickel ions, which accumulate on the particle surface as NiO, increasing interfacial resistance and reducing electrochemical performance. Understanding this degradation mechanism is crucial for developing high-energy cathodes for sodium-ion batteries.
Conclusion
Air degradation encompasses a wide range of processes affecting various pollutants and materials. From the degradation of VOCs in air purifiers to the chemical breakdown of PAHs and the impact of air exposure on organic solar cells and sodium-ion battery cathodes, understanding these processes is essential for improving air quality and the longevity of materials exposed to air. Continued research and advanced modeling are vital for developing effective strategies to mitigate air degradation.
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