Chemistry in glow discharges of H2/O2 mixtures: diagnostics and modelling. (8th January 2015)

• Record Type: Journal Article
• Authors: Jiménez-Redondo, M; Carrasco, E; Herrero, V J; Tanarro, I
• Is Part Of: Plasma sources science & technology. Volume 24:Number 1(2015:Feb.)
• Publication Date: 2015-01-08
• Subjects: plasma kinetics -- H2 + O2 low pressure discharges -- plasma diagnostics and modelling -- ions and neutrals plasma chemistry; Plasma (Ionized gases) -- Periodicals; 530.44
• DOI: 10.1088/0963-0252/24/1/015029
• Languages: English
• ISSNs: 0963-0252

Abstract

Abstract: The chemistry of low pressure H2 +O2 discharges with different mixture ratios has been studied in a hollow cathode dc reactor. Neutral and positive ion distributions have been measured by mass spectrometry, and Langmuir probes have been used to provide charge densities and electron temperatures. A simple zero order kinetic model including neutral species and positive and negative ions, which takes into account gas-phase and heterogeneous chemistry, has been used to reproduce the global composition of the plasmas over the whole range of mixtures experimentally studied, and allows for the identification of the main physico-chemical mechanisms that may explain the experimental results. To our knowledge, no combined experimental and modelling studies of the heavy species kinetics of low pressure H2 + O2 plasmas including ions has been reported before. As expected, apart from the precursors, H2 O is detected in considerable amounts. The model also predicts appreciable concentrations of H and O atoms and the OH radical. The relevance of the metastable species O( 1 D) and O2 ( a 1 Δ g ) is analysed. Concerning the charged species, positive ion distributions are dominated by H3 O + for a wide range of intermediate mixtures, while and are the major ions for the higher and lower H2 /O2 ratios, respectively. The mixed ions OH +, H2 O + and are also observed in small amounts. Negative ions are shown to have a limited relevance in the global chemistry; their main contribution is the reduction of the electron density available for electron impact processes.