Download or read book Atomistic-Level Investigation for Selected Metal-based Catalytic Reactions Utilizing the ReaxFF Reactive Force Field written by Wenbo Zhu and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Metal-based catalytic reactions have been extensively studied dues to their wide variety of applications in energy productions, storages, and new high-energy material fabrications. Although multiple experimental approaches were developed and utilized, it is still challenging to obtain a full perception of the detailed chemical events happening during these catalytic reactions because of the complex reaction environment and composition of the reactive species. Simulation approaches, such as reactive molecular dynamics methods, have the potential to solve these challenges, facilitating understanding chemical events in metal-based catalytic reaction at the atomistic-level. These simulations allow us to create a desirable system that only contains the target species to avoid contaminants that are difficult to be removed in experiment. In addition, simulation methods can create some special environments (such as extremely high pressure and temperature) that are difficult to be handled in experiments. This dissertation will discuss a series of studies related to the metal-based catalytic reactions explored by the ReaxFF reactive force field simulation approach. Topics included hydrocarbon conversions in Cu-based chemical looping combustion, the (Polyvinylidene fluoride) PVDF conversions on alumina particles, the impact of the CaO/MgO particle to the Low Speed Pre-ignition (LSPI) in combustion engine, and the stability of the silver oxide at high temperature with gold addition. Below follows a brief description of these topics. In the study of the Cu-based Chemical Looping Combustion (CLC), reactive molecular dynamics simulations were performed to study the oxidation and combustion reactor separately. In both reactors, we found the hydrocarbons follows the rules of 'Sequential neighboring abstraction' in which the Cu surface prefers abstracting gas phase hydrocarbons from the middle position of the carbon chain, followed by the neighboring abstractions of the functional groups. In addition, from the study of the selected solid carbon fuels' conversion with a CuO practice, we found that solid carbon fuels contain different reaction kinetics depending upon CuO decomposition temperature. Below the CuO decomposition temperature, the surface interactions between solid fuels and CuO particles are favorable. When the temperature raised up above 1500 K, solid fuel combustions with O2 becomes the dominant reaction, and this observation is in good agreement with our collaborators experimental results. In the study of the aluminum/PVDF composite, a series of PVDF/Alumina systems were simulated utilizing the ReaxFF reactive dynamics method. Results indicate that the PVDF conversions with alumina is a multi-stage process: A single F/H from PVDF was chemisorbed by alumina surface to generate unsaturated PVDF molecules; followed by HF formation from the unsaturated PVDF fragmentation. Gas phase HF molecules then would rapidly corrode alumina surface. Hydroxyls on alumina surface would combine to produce water dissociated to the gas phase. The chemisorbed F on alumina will then aggregate to form aluminum fluoride networks. The Low Speed Pre-ignition (LSPI) is an undesirable event that happened before the normal spark ignition, which cause serve damages to combustion engines. The ReaxFF based NVE simulations (Simulation with conserved atom number, size, and total energy) for CO2 adsorption by CaO/MgO nanoparticles were performed to rationalize the reported experiment result that the presence of MgO will prohibit LSPI. Results show that CaO particle adsorbing CO2 will produce more heat release to increase the environment temperature to cause LSPI. On the other hand, there was no such temperature peak when CO2 was adsorbed by an MgO particle. Experiments found the silver oxide particle was stable at 450 °C with gold addition, which was rationalized by the ReaxFF reaction scan analysis. Results confirm alloying of Au into Ag will largely decrease the energy barrier of O2 dissociation while also increase the Ag-O binding energy on the Au-Ag surface. As these wide range of studies illustrated, the ReaxFF simulation approach and analysis methods discussed in this dissertation have demonstrated their ability and transferability and have become the powerful tools for studying complex surface chemistry.