Role of Plasma Catalysis in the Microwave Plasma‐Assisted Conversion of CO2

Abstract

Climate change and global warming caused by the increasing emissions of greenhouse gases (such as CO 2) recently attract attention of the scientific community. The combination of plasma and catalysis is of great interest for turning plasma chemistry in applications related to pollution and energy issues. In this chapter, our recent research efforts related to optimization of the conversion of CO 2 and CO 2 /H 2 O mixtures in a pulsed surface-wave sustained microwave discharge are presented. The effects of different plasma operating conditions and catalyst preparation methods on the CO 2 conversion and its energy efficiency are discussed. It is demonstrated that, compared to the plasma-only case, the CO 2 conversion and energy efficiency can be enhanced by a factor of ∼2.1 by selecting the appropriate conditions. The catalyst characterization shows that Ar plasma treatment results in a higher density of oxygen vacancies and a comparatively uniform distribution of NiO on the TiO 2 surface, which strongly influence CO 2 conversion and energy efficiencies of this process. The dissociative electron attachment of CO 2 at the catalyst surface enhanced by the oxygen vacancies and plasma electrons may explain the increase of conversion and energy efficiencies in this case. A mechanism of plasma-catalytic conversion of CO 2 at the catalyst surface in CO 2 and CO 2 /H 2 O mixtures is proposed.

An overview of CO2conversion in a microwave discharge: the role of plasma-catalysis

“…Up to now, nonthermal plasmas have been shown to be an effective media for CO 2 decomposition . Different types of plasma have already been used for CO 2 conversion, including dielectric barrier discharges (DBD) [2][3][4][5][6][7], glow discharges [8], radio frequency (RF) discharges [9], microwave (MW) discharges [10][11][12][13][14][15]21], gliding arc discharges [16,17] and corona discharges [18]. The highest energy efficiency (nearly 90%) for pure CO 2 conversion was reported in the MW plasma operating with supersonic gas flows, however, there is always a trade-off between the energy efficiency and conversion efficiency, resulting in very low conversion efficiency in this case [13].…”

“…Up to now, the majority of the plasma catalyst research work is related to DBDs [24]. There has been limited effort in combining catalyst with microwave plasma [10,11,15]. It is well known that due to its high degree of non-equilibrium, microwave plasma possesses highly vibrational states of CO 2 molecules, which are energy-efficient for CO 2 decomposition [1].…”

Progress in Plasma-Assisted Catalysis for Carbon Dioxide Reduction

“…As a result of previous studies on CO 2 decomposition in plasma, it was concluded that higher pressures and lower values of reduced electric field make the vibrational excitation mechanism more favorable than the electronic excitation mechanism, explaining the higher energy efficiency of these types of discharges (e.g. MW, GAP) [1,3,22,26,28,32,33,35,37,38].…”

“…In the context of plasma catalysis, the synergy is referring to a surplus effect of combining the plasma with catalyst, namely, when the resulting effect has a higher impact than the sum of their individual impacts. In several studies, the combination of plasma and catalysts has been found to have synergistic effects [34,35,61,62]. A highly important synergistic effect of plasma catalysis is promotion of catalyst activity at reduced temperatures, and hence, a significant reduction in the energy cost for activating the catalyst [34].…”

Synthesis and Characterization of 40 wt % Ce0.9Pr0.1O2–δ–60 wt % NdxSr1−xFe0.9Cu0.1O3−δ Dual-Phase Membranes for Efficient Oxygen Separation

“…Besides the application of the separation of oxygen from air, MIEC membranes used in membrane reactors are getting increasing attention to couple the reaction and separation processes to save energy and simplify the process [ 21 , 22 , 23 , 27 , 28 ]. Plasma technologies have attracted increasing attention as a timely flexible method for CO 2 conversion and utilization [ 29 , 30 , 31 , 32 , 33 ]. For example, plasma-assisted MIEC membranes, used to separate oxygen radicals without additional external heating from the decomposition products, provide an efficient way to enhance the overall CO 2 conversion efficiency via inhibiting the reverse reactions [ 27 , 28 ].…”