ELECTROSTATIC CHARGING OF SOLID AND GAS PHASES AND APPLICATION TO CONTROLLING CHEMICAL REACTIONS by XIAOZHOU SHEN Submitted in partial fulfillment of the requirements For the degree of Doctor of Philosophy Thesis Advisor: Daniel J. Lacks, Ph. D. Department of Chemical and Biomolecular Engineering CASE WESTERN RESERVE UNIVERSITY August, 2017 CASE WESTERN RESERVE UNIVERSITY SCHOOL OF GRADUATE STUDIES We hereby approve the thesis/dissertation of Xiaozhou Shen candidate for the degree of Doctor of Philosophy *. Committee Chair Daniel J. Lacks Committee Member R. Mohan Sankaran Committee Member Heidi B. Martin Committee Member Hatsuo Ishida Date of Defense 7/7/2017 *We also certify that written approval has been obtained for any proprietary material contained therein. Table of Contents Table of Contents ................................................................................................................ 1 Chapter 1 Thesis introduction – electrostatic charging on surfaces and in gases ............... 1 Introduction to electrostatics ..................................................................... 1 Electrostatics developed on surfaces ......................................................... 2 Electrostatics in gas phase ......................................................................... 8 Non-thermal plasmas for gas conversion ................................................ 10 Chapter 2 Multiscale simulation techniques ..................................................................... 21 Quantum mechanics calculation .............................................................. 22 Micro-kinetic simulation (hybrid simulation) ......................................... 30 Chapter 3 Contact charging between quartz (0001) and sapphire (0001) ........................ 39 Description of the modeling system ........................................................ 39 Results and discussion (compare with experiment) ................................ 41 Chapter 4 Direct methane conversion by dielectric barrier discharge .............................. 51 Description of the DBD model ................................................................ 51 Experimental setup .................................................................................. 54 Intuitive framework ................................................................................. 55 Modeling Setup ....................................................................................... 59 Gas phase combustion reactions ............................................................. 66 Thermo–chemistry of gas phase species ................................................. 69 I Results and discussion (compare with experiment) ................................ 70 Chapter 5 Plasma catalysis – effects of asymmetric vibration of CO2 splitting on Ni surface ............................................................................................................................. 101 Description of the model ....................................................................... 101 Results and discussion ........................................................................... 107 Chapter 6 Conclusions and Future Work ........................................................................ 116 Appendix ......................................................................................................................... 119 Bibliography ................................................................................................................... 136 II List of Tables Table 1 Triboelectric series proposed by various researchers15 .......................................... 6 Table 2 Typical parameters of a microdischarge .............................................................. 52 Table 3 the number of microdischarge pulses (meso-reactors) that a plug of gas molecules with constant flow rate will pass when going through reactor with reactor volume............................................................................................................................... 62 Table 4 Electron Impact Target Species and Cross Section Sources ................................ 66 Table 5 Electron impact cross sections ............................................................................. 68 Table 6 list of electron–ion dissociative recombination reactions and their reaction rate coefficients128 .................................................................................................................... 69 Table 7 Tabular summary of the positions of CO2 molecules in the 20 systems. .......... 105 III List of Figures Figure 1.1 Schematic graph representing the 3 charging mechanisms: (a) electron transfer mechanism, (b) ion transfer mechanism, and (c) material transfer mechanism ................. 5 Figure 1.2 Examples of plasma and their corresponding ranges of plasma density and temperature19 ....................................................................................................................... 9 Figure 1.3 Typical dielectric-barrier discharge configuration58 ....................................... 13 Figure 1.4 The microdischarges in an atmospheric pressure dielectric barrier discharge. (a) shows the end-on view with exposure time of 20 ms (original size: 6 cm×6 cm) 58; (b) represents the side view61. ................................................................................................. 14 Figure 1.5 Circuit model of a microdischarge58 ................................................................ 14 Figure 1.6 Vibration mode of CO2 molecule .................................................................... 19 Figure 2.1 Levels of simulation techniques ...................................................................... 21 Figure 2.2 Correlation between effective quantum number and velocity of oxygen for asymmetric vibration mode and symmetric vibration mode ............................................. 29 Figure 2.3 schematic representation of our overall modeling process .............................. 30 Figure 2.4 Analogue of experiment setup and 1D plug flow reactor (PFR) model. The occurrence of filaments in experimental setup is randomly distributed throughout the entire reactor space, while in simulation is assumed to ignite at specific spot, which is illustrated in orange color. ................................................................................................ 31 Figure 3.1 System examined in the calculations. (left) view from the side, with quartz on left and sapphire on right; (middle) quartz [0001] surface; (right) sapphire [0001] surface. IV In these figures, oxygen is red, silicon is yellow, aluminum is brown, and hydrogen is white. ................................................................................................................................. 41 Figure 3.2 Calculation results for the total energy of the quartz-sapphire system as a function of separation between the quartz and sapphire [0001] surfaces. The energy given is relative to the energy in the limit of large separation .................................................... 42 Figure 3.3 Charge on sapphire and quartz slabs obtained from calculations, using Mullikan Population Analysis........................................................................................... 43 Figure 3.4 Net surface charge densities from contact charging of sapphire against quartz; open circles (○) represent sapphire trials, open squares (□) represent quartz trials, filled circles (•) represent sapphire average values, filled squares (■) represent quartz average values. ............................................................................................................................... 44 Figure 3.5 Electrostatic potential energy obtained from DFT calculations of surfaces separated by 3 Å. ............................................................................................................... 46 Figure 3.6 Charge on sapphire slab obtained from calculations. The line is an exponential fit to the data. .................................................................................................................... 47 Figure 4.1 Typical charge-voltage waveforms for a filament DBD ................................. 51 Figure 4.2 Typical power profile for DBD, with the correspondent electron temperature and electron density. ......................................................................................................... 53 Figure 4.3 Schematics of experimental setup ................................................................... 54 Figure 4.4 Schematic representation of our intuitive framework ..................................... 56 Figure 4.5 Power profile as a function of time ................................................................. 63 Figure 4.6 Schematic top view of the unwrapped surface of reactor wall. The white squares represent the area where microdischarges are occurring; the blue squares V represent the area where there is no discharge. (a) simultaneous occurring of microdischarges, where the discharges spread randomly on the surface of reactor wall; (b) occurring of microdischarges with the assumption that the micro-discharges always occur at the same spots; (c) is an equivalent scenario to (b) when the gas mixture travelling through the filamentary region. ........................................................................ 65 Figure 4.7 Applied power deposition