VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY TA THI LUONG QUANTUM SIMULATION OF THE ADSORPTION OF TOXIC GASES ON THE SURFACE OF BOROPHENE MASTER'S THESIS Hanoi, 2019 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY TA THI LUONG QUANTUM SIMULATION OF THE ADSORPTION OF TOXIC GASES ON THE SURFACE OF BOROPHENE MAJOR: NANOTECHNOLOGY CODE: PILOT RESEARCH SUPERVISOR: Dr. DINH VAN AN Hanoi, 2019 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com ACKNOWLEDGMENT First of all, I sincerely appreciate the great help of my supervisor, Dr. Dinh Van An. Thank you for all your thorough and supportive instructions, your courtesy, and your encouragement.
This thesis absolutely could not be conducted well without your dedicated concerns. Second of all, I would like to show my gratefulness to Prof. Morikawa Yoshitada, my supervisor during my internship time at Osaka University. Your guidance helps me a lot to get a more profound insight into my research topic as well as research- related works.
Third of all, I want to express my warm thanks to my classmate, Pham Trong Lam. Thanks to you, I got acquaintance more easily with computational material science. Thank you for your willingness to help; it means a lot to me. Last but not least, I also would like to thank Vietnam Japan University and the staff working here for their necessary supports.
This research is funded by National Foundation for Science and Technology Development (NAFOSTED) under grant number 103. i LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com CONTENTS Page Acknowledgment .ii LIST OF TABLES. iv LIST OF FIGURES. v LIST OF ABBREVIATIONS.
viii Chapter 1 INTRODUCTION .1 Background of the research .2 Objectives and subjects of the research .1 Adsorbent material: Borophene .3 Toxic gases adsorption on two-dimensional materials .1 Gas adsorption on other two-dimensional materials .2 Adsorption application of borophene .9 Chapter 2 THEORETICAL BASICS AND METHODS .1 Density Functional Theory .3 Bader charge analysis .17 Chapter 3 RESULTS AND DISCUSSION .2 Energetically favorable configurations .3 Adsorption energy and reaction length .1 Adsorption energy and adsorption distance in comparison of vdW- employed functionals .2 Comparison of adsorption energy among gases .4 Potential energy surface .6 Charge transfer characteristic .39 ii LUAN VAN CHAT LUONG download : add luanvanchat@agmail.1 Charge analysis of the (CO – borophene) system .2 Charge analysis of the (CO2 - borophene) system .3 Charge analysis of the (NO - borophene) system. Charge analysis of the (NO2 - borophene) system. Charge analysis of the (NH3 - borophene) system. 49 iii LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com LIST OF TABLES Page Table 1.
The adsorption energy of CO, CO2, NO2, NO, and NH3 on different two- dimensional materials (eV) .1 Calculated lattice constants of β12 borophene vs. Bader charge analysis of the (CO - borophene) system. Bader charge analysis of the (CO2 – borophene) system. Bader charge analysis of the (NO – borophene) system.
Bader charge analysis of the (NO2 – borophene) system. Bader charge analysis of the (NH3 – borophene) system .44 iv LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com LIST OF FIGURES Page Figure 1. Elements predicted to be precursors of synthetic elemental 2D materials and their synthetic methods.2 Borophene assumed to be synthesized on Ag (111) substrate (a) buckled triangular borophene, (b) β12 borophene, and (c) χ3 borophene. The flow chart of gas absorbing calculations .1 The calculated supercell of β12 boron sheet after optimization.
Band structure and DOS of the unit cell of β12 borophene. Top view and side view of the most stable configurations of CO on borophene. Top view and side view of the most stable configurations of CO2 on borophene. Top view and side view of the most stable configurations of NH3 on borophene.
Top view and side view of the most stable configurations of NO2 on borophene. Top view and side view of the most stable configurations of NO on borophene using 3 different vdW functionals. Adsorption energy change accordingly to the distance of the (a) CO and (b) CO2 molecule and borophene in comparison. Adsorption energy change accordingly to the distance of the (a) NH3 and (b) NO2 molecule and borophene.
Adsorption energy change accordingly to the distance between NO molecule and borophene. Comparison among gases of the shortest distance between gas molecules and substrate (dz), the distance from the massed center of gas molecules to the substrate (dc), and the adsorption energy (Ea) using optPBE-vdW functional. Potential energy surface of CO adsorbed borophene. Potential energy surface of CO2 adsorbed borophene.
The projected binding energy of NH3 along the surface of borophene. Potential energy surface of borophene-NO. Potential energy surface of NO2 – borophene. Band structure and DOS of CO - borophene.
Band structure and DOS of CO2 - borophene .37 v LUAN VAN CHAT LUONG download : add luanvanchat@agmail. Band structure and DOS of NH3 - borophene. Band structure and DOS of NO - borophene. Band structure and DOS of NO2 - borophene.
Charge density difference after CO adsorption illustrated using isosurface (isosurface level = 0. Charge density difference after CO2 adsorption illustrated using isosurface (isosurface level = 0. Charge density difference after NO adsorption (isosurface level = 0. Charge density difference after NO2 adsorption illustrated using isosurface (isosurface level = 0.
Charge density difference after adsorbing NH3 (isosurface level = 0. Charge transfer of CO, CO2, NH3, NO, NO2, and SO2 and borophene .45 vi LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com LIST OF ABBREVIATIONS 2D Two-dimensional DFT Density Functional Theory VASP Vienna Ab initio Software Package vdW van der Waals DOS Density of state KS Kohn-Sham MO Molecular orbital HF Hartree-Fock 3D Three-dimensional PAW Projector Augmented Wave vii LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com ABSTRACT 2D materials have attracted significant research interest due to their excellent characteristics. Borophene, a new member of the 2D material family, was proven that it has a unique structure and promising properties by both empirical and theoretical studies. In this study, the adsorption configuration, adsorption energy of toxic gas molecules (CO, NO, CO2, NH3, and NO2) on 12 – borophene was investigated by first – principle calculations using three van der Waals correlation functionals: revPBE-vdW, optPBE-vdW, and vdW-DF2.
The most stable configurations and diffusion possibilities of the gas molecules on the 12 – borophene surface were determined visually by using Computational DFT-based Nanoscope [10]. The nature of bonding and interaction between gas molecules and 12 – borophene are also disclosed by using the density of states analysis and Bader charge analysis. The obtained results are not only considerable for understanding gas molecules on borophene but also useful for technological applications of borophene in very near future. Keywords: 12 – borophene, DFT, adsorption, toxic gases viii LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com CHAPTER 1 INTRODUCTION 1.1 Background of the research In the present society, when industrialization and urbanization are increasing sharply, air pollution becomes a severe global problem.
Air pollution can affect human health directly or indirectly. According to WHO (2017) data, air pollution causes 1 in 9 deaths worldwide while ambient air pollution caused 7.6% deaths over the world in 2016, which is included 4.2 million premature deaths. Air pollution might lead to stroke, lung cancer, stroke, chronic obstructive, heart disease and acute respiratory infections in children. Worldwide ambient air pollution accounts for: 29% of deaths and diseases caused by lung cancer 17% of all patients related to acute lower respiratory infection 24% of all deaths from stroke 25% of all deaths and disease from ischaemic heart disease 43% of all deaths and disease from chronic obstructive pulmonary disease [46] To decrease the impacts of air pollution, detecting pollutants is the first work needed to do before carrying out the processing procedure [46].
Hence, the things here is discovering good material which has high sensitivity and selectivity with poisonous gases, which are the significant pollutants causing air pollution, toward creating an effective sensor to detect these pollutants effectively. Overall, low-dimensional materials are potential adsorbents on gas adsorbing applications due to their high surface-to-volume ratio. Borophene is a new noble two-dimensional material, which is newly successfully synthesized [28]. Borophene is expected to have intriguing characteristics like graphene, initially expresses the outstanding mechanical and electronic performance such as existing spin gapless 1 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com Dirac cone, and supposed to be metallic for most phases [11].
Beside those promising properties, borophene also has a high surface-to-volume ratio due to its two-dimensional existence. Borophene thus is a promising candidate for adsorption of poisonous applications.2 Objectives and subjects of the research Toward developing gas sensor materials, pollutants absorbability of potential materials is investigated by using quantum simulation. This research aims to discover a potential material for filtering or sensing toxic gases in the ambient atmosphere contributing to air pollution mitigation and enhancing community health. As follows, borophene as a potential candidate will be investigated the gas adsorbing performance.
The obtained results will be not just for understanding of borophene, a new material, but for the development of gas sensor at the nanoscale as well. Hence, the research subject here is the complex system of toxic gas molecules on the adsorbent material.1 Adsorbent material: Borophene As the rising of graphene after the Nobel Prize in Physics to Andre Geim, Konstantin Novoselov in 2010, 2D materials intrigue many interests of scientists worldwide because of their superlative physiochemical characteristics. Moreover, there still exists much unexplored promising information about such nanomaterials. 2D materials are atomically thin sheets that exhibit unique electronic, optical, and mechanical properties with remarkable potential for technological applications and a plethora of unknown fundamental science [29].
Regarding adsorption related problems, 2D materials express as one of the most prospective candidates due to their unique characteristics and its high specific surface area. With tremendous attention from researchers, more and more new 2D materials are synthesized recently.1 shows elements able to form synthetic elemental 2D materials and synthesis methods. 2 LUAN VAN CHAT LUONG download : add luanvanchat@agmail. Elements predicted to be precursors of synthetic elemental 2D materials and their synthetic methods.
Adapted from ―Synthesis and chemistry of elemental 2D materials‖, by A. Mannix et al., 2017, Nature Reviews Chemistry, 1, 1-15, Copyright [2017] by Macmillan Publishers Limited. Boron is one of the most complicated elements in terms of chemical bond in three- dimensional structure due to its 3-electron outer shell configuration. This fact prevents the fulfillment of the octet rule, leading to irregular ‗electron poor‘ bonding configurations [41].
A striking feature of boron is that B12 icosahedral cages occur as the building blocks in bulk boron and many boron compounds [1]. Regarding its two-dimensional existence, boron also expresses its diversity of polymorphs on different substrates or cultivation conditions [26][13]. Boron 2D sheets, which is so-called borophene, is predicted by first principle calculations to have various allotropes. Notably, these polymorphs of borophene have been predicted to be metallic or semi-metallic where boron in 3D bulk phase is an insulator.
[27] Recently, borophene has been successfully synthesized by two independent groups Mannix et al. (2015) and Feng et al. From these empirical data, borophene expresses as a metallic material which agrees with 3 LUAN VAN CHAT LUONG download : add luanvanchat@agmail.com previous theoretical predictions. From STM images and LEED diffraction, borophene structures are confirmed to have two main polymorphs when using Ag (111) as a substrate: 12 and 3 (also called as 1/6 and 1/5, respectively) as shown in Figure 1.2 Borophene assumed to be synthesized on Ag (111) substrate (a) buckled triangular borophene, (b) β12 borophene, and (c) χ3 borophene.
Adapted from ―Two- dimensional boron: Structures, properties and applications‖, by Zhang, Penev, & Yakobson, 2017, Chemical Society Reviews, 46(22), 6746-6763. Copyright [2017] by The Royal Society of Chemistry.