Gas-Phase Chemistry in Inductively Coupled Plasmas for NO Removal from Mixed Gas Systems

Using Fundamental Spectroscopy to Elucidate Kinetic and Energetic Mechanisms within Environmentally Relevant Inductively Coupled Plasma Systems

Understanding energy distributions and kinetic processes in N_xO_y plasma systems is vital to realizing their potential in a range of applications, including pollution abatement. Energy partitioning between degrees of freedom and multiple molecules formed within N_xO_y plasma systems (N₂, N₂O, N₂/O₂) was investigated using both optical emission and broadband absorption spectroscopies. Specifically, we determined electron temperatures (T_e) as well as rotational (T_R) and vibrational (T_V) temperatures for various N₂ (B³Π_g and C³Π_u) and NO (X²Π and A²Σ⁺) states. T_R and T_V for both molecules (regardless of state) show a strong positive correlation with applied plasma power, as well as a negative correlation with system pressure. In all cases, T_V values are significantly higher than T_R for both species, suggesting vibrational modes are preferentially excited over rotational degrees of freedom. Time-resolved optical emission spectroscopy was utilized to determine rate constants, providing mechanistic insight and establishing the relationships between system parameters and plasma chemistry. Ultimately, the combination of these data allows us to glean information regarding both the kinetics and energetics of N₂ and NO molecules formed within nitrogen- and oxygen-containing plasma systems for potential applications in gas remediation of pollutants.

Effects of gas temperature on NO(x) removal by dielectric barrier discharge

The purpose of this investigation is to discuss the effect of gas temperature on NO(x) removal by dielectric barrier discharge. The Boltzmann equation was used to analyse the electron distribution function in the reactor, and experiments were conducted to find out the effects of different temperatures. The calculation results show that, with a rise in the temperature, E/N increases, increasing the ionization rate. When the ratio of electric field strength to total gas density (E/N) rises from 50 to 150 Td, the ionization rate and electron mean energy increase by 2.0 x 10(5) and 2.3, respectively. The experiments show that in the NO/N2 system, when the temperature increases to 1 30 degrees C and the applied voltage is 11.1 kV, the discharge power is 44.7 W, which is higher than the discharge power of 35.4 W found at 25 degrees C; in the NO/O2/N2 system, an increase in the temperature increases the decomposition of active O3 species, producing a negative effect on NO oxidation; in the NO/O2/N2/C2H4 system, when the temperature increases, the quantity of active species HO2 increases and the NO removal reaction rate increases, reflecting an obvious improvement in the NO removal; and in the NO/O2/N2/C2H4/H2O system, at 25 degrees C, 90 degrees C, and 130 degrees C, when the energy density is 239.7 J L(-1), the NO removal efficiencies are 52.8%, 66.4%, and 71.0%, respectively.

Effect of ion energies on the surface interactions of NO formed in nitrogen oxide plasma systems

The contributions of various gas-phase species in surface reactions are of significant value to assess and improve catalytic substrates for abatement of vehicular emissions. The impact of ions on surface scatter of NO radicals is investigated with an aim toward improving and tailoring surfaces for the reduction or removal of nitrogen oxide (N(x)O(y)) species via inductively coupled plasmas (ICPs). Nascent ions are monitored via mass spectrometry and energy analysis for a variety of N(x)O(y) precursor gases. The total average ion energy (<E(i)>(total)) determined for all ions within each respective plasma system shows a strong positive correlation with applied rf power and a negative correlation with system pressure. The imaging of radicals interacting with surfaces (IRIS) technique was used to determine the role ions play in the surface scatter of NO radicals. The net effect of ions on substrate processing is largely dependent upon <E(i)>(total). Scatter coefficients (S), determined for ion-limited and ion-rich plasma systems were used to correlate <E(i)>(total) and scatter. The resultant effect is that ions play a substantial role in scatter of NO only when <E(i)>(total) > ~50 eV. The majority of systems studied contained ions below this energy threshold, suggesting knowledge of ion energies is integral to appropriately controlling the chemistry occurring between the gas-phase and surface.