Tuning plasma parameters to control reactive species fluxes to substrates in the context of plasma catalysis
Tuning plasma parameters to control reactive species fluxes to substrates in the context of plasma catalysis
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DOI：
10.1088/1361-6463/abe89a
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发表时间：
2021-05
期刊：
影响因子：
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通讯作者：
Jingkai Jiang;P. Bruggeman
中科院分区：
文献类型：
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作者：
Jingkai Jiang;P. Bruggeman
与热催化相比，等离子体催化中导致化学品转化的关键反应等离子体产生的气相物种迄今尚未确定。这个突出的问题主要是由于等离子体产生的物种本身种类繁多，以及控制和测量活性物种的鸡尾酒中每个组分到(催化)底物的通量的挑战。在这篇文章中，我们探索了控制与等离子体催化有关的主要反应物种流向射频驱动Ar-O2等离子体射流流出物中底物的可能性。用分子束质谱仪(MBMS)定量了主要反应物种(O、O2(a 1Δg)、O 3和离子)的绝对物种密度，以评估利用处理距离、O2混合浓度、等离子体耗散功率、射频调制频率和占空比以及进气流量改变优势物种密度的可能性。选定的实验结果也与拟一维推流模型进行了比较。通过改变处理距离和射频调制频率，可以有效地分离出短寿命和长寿命物种。此外，通过调节O2混合浓度，可以改变O2(a1Δg)和O3浓度的比例。离子通量和氧通量的变化趋势在几乎所有的研究参数中都非常相似。尽管如此，气体流量能够显着改变等离子体射流流出物中O和离子密度的比率。进一步讨论了表面相关损失概率和边界层反应对物质流向衬底的影响，以及这种影响如何与MBMS密度测量定性地联系在一起。
The key reactive plasma-produced gas phase species responsible for the enhanced conversion of chemicals in plasma catalysis compared to thermal catalysis have to date not been identified. This outstanding question is mainly due to the inherent large variety of plasma-produced species and the challenge of controlling and measuring the flux of each constituent of the cocktail of reactive species to a (catalytic) substrate. In this paper, we explore the possibility to control the dominant reactive species fluxes, relevant for plasma–catalysis, to a substrate in the effluent of an RF driven Ar–O2 plasma jet. The absolute species densities of the major reactive species (O, O2(a 1Δg), O3 and ions) were quantified by molecular beam mass spectrometry (MBMS) to assess the possibility of using treatment distance, O2 admixture concentration, plasma dissipated power, RF modulation frequency and duty cycle as well as the feed gas flow rate to alter the dominant species densities. Selected experimental results were also compared with a pseudo-1D plug flow model. The short-lived and long-lived species can be effectively separated by changing the treatment distance and the RF modulation frequency. Furthermore, adjusting the O2 admixture concentration enables to change the ratio of the O2(a 1Δg) and O3 density. The changes in the trend of ion and O flux were found to be very similar for nearly all investigated parameters. Nonetheless the gas flow rate was able to significantly change the ratio of the O and ion density in the plasma jet effluent. The impact of the surface-dependent loss probability and boundary layer reactions on the species flux to a substrate and how this qualitatively relates to the MBMS density measurements is further addressed.