Plasma-photocatalytic conversion of CO2 at low temperatures: Understanding the synergistic effect of plasma-catalysis

A coaxial dielectric barrier discharge (DBD) reactor has been developed for plasma-catalytic conversion of pure CO2 into CO and O2 at low temperatures (<150°C) and atmospheric pressure. The effect of specific energy density (SED) on the performance of the plasma process has been investigated. In the absence of a catalyst in the plasma, the maximum conversion of CO2 reaches 21.7% at a SED of 80kJ/L. The combination of plasma with BaTiO3 and TiO2 photocatalysts in the CO2 DBD slightly increases the gas temperature of the plasma by 6-11°C compared to the CO2 discharge in the absence of a catalyst at a SED of 28kJ/L. The synergistic effect from the combination of plasma with photocatalysts (BaTiO3 and TiO2) at low temperatures contributes to a significant enhancement of both CO2 conversion and energy efficiency by up to 250%. The UV intensity generated by the CO2 discharge is significantly lower than that emitted from UV lamps that are used to activate photocatalysts in conventional photocatalytic reactions, which suggests that the UV emissions generated by the CO2 DBD only play a very minor role in the activation of the BaTiO3 and TiO2 catalysts in the plasma-photocatalytic conversion of CO2. The synergy of plasma-catalysis for CO2 conversion can be mainly attributed to the physical effect induced by the presence of catalyst pellets in the discharge and the dominant photocatalytic surface reaction driven by the plasma

The role of thermal energy accommodation and atomic recombination probabilities in low pressure oxygen plasmas

International audienceSurface interaction probabilities are critical parameters that determine the behaviour of low pressure plasmas and so are crucial input parameters for plasma simulations that play a key role in determining their accuracy. However, these parameters are difficult to estimate without in situ measurements. In this work, the role of two prominent surface interaction probabilities, the atomic oxygen recombination coefficient ? O and the thermal energy accommodation coefficient ? E in determining the plasma properties of low pressure inductively coupled oxygen plasmas are investigated using two-dimensional fluid-kinetic simulations. These plasmas are the type used for semiconductor processing. It was found that ? E plays a crucial role in determining the neutral gas temperature and neutral gas density. Through this dependency, the value of ? E also determines a range of other plasma properties such as the atomic oxygen density, the plasma potential, the electron temperature, and ion bombardment energy and neutral-to-ion flux ratio at the wafer holder. The main role of ? O is in determining the atomic oxygen density and flux to the wafer holder along with the neutral-to-ion flux ratio. It was found that the plasma properties are most sensitive to each coefficient when the value of the coefficient is small causing the losses of atomic oxygen and thermal energy to be surface interaction limited rather than transport limited

Cl atom recombination coefficients in a Cl<SUB>2</SUB> ICP determined by TALIF

International audienc

Seeing Inside Plasma Etch Reactors: from diagnostics to sensors for control

International audienc

Influence of argon fraction on plasma parameters in H

Low-pressure H2-N2 mixture pulsed DC plasmas with a cathodic cage (active screen) are widely used for plasma nitriding applications. In this study, the low-pressure H2-N2 mixture plasma with a cathodic cage generated by 50 Hz pulsed DC source is investigated with triple Langmuir probe and optical emission spectroscopy. The electron temperature (TeLP) and electron number density (ne) are measured using a triple Langmuir probe (TLP). The excitation temperature (TexcOES) is calculated spectroscopically using Boltzmann plot method whereas nitrogen dissociation fraction is estimated using actinometry as well as the intensity ratio method (IN (746.83 nm)/IN2(337.1 nm)). The results show that the electron and excitation temperatures, electron density and nitrogen atomic species density [N] all increase with the argon admixture, however, the important molecular ionized species density [N2+] significantly decreases beyond 30% addition. This study provides useful information about the influence of the argon addition on plasma parameters and active species generation. As a result it helps to optimize the plasma nitriding system as a function of argon admixture to avoid random trials in the processing