Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.Nghiên cứu khả năng xử lý DDT và γHCH trên một số kim loại và oxide kim loại mang trên gC3N4 bằng phương pháp phiếm hàm mật độ liên kết chặt.MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF EDUCATION PHAM THI BE STUDY ON THE ABILITY TO PROCESS DDT AND γ HCH ON SOME METALS AND METAL OXIDES CARRIED ON g C3N4 BY THE DENSITY FUNCTIONAL T.
MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF EDUCATION PHAM THI BE STUDY ON THE ABILITY TO PROCESS DDT AND γ-HCH ON SOME METALS AND METAL OXIDES CARRIED ON g-C3N4 BY THE DENSITY FUNCTIONAL TIGHT BINDING METHODS Specialization: Theoretical and Physical Chemistry Code: 9440119 SUMMARY OF CHEMICAL PhD THESIS HA NOI – 2022 The thesis was completed at Department of Chemistry – Hanoi University of Education SCIENTIFIC INSTRUCTORS: Prof Dr Nguyen Ngoc Ha Dr Nguyen Thi Thu Ha Review 1: Prof Dr Tran Thai Hoa Review 2: Prof Dr Le Thanh Son Review 3: Prof Dr Tran Dai Lam The thesis will be presented before the Board of thesis review at Hanoi University of Education on .h day month year The thesis can be found at: National Library, Hanoi or the library of Hanoi National University of Education LIST OF PUBLISHED BY AUTHOR Phạm Thị Bé (2020), “Nghiên cứu lý thuyết khả hấp phụ Dichlorodiphenyltrichloroethane than hoạt tính than hoạt tính biến tính sắt phương pháp phiếm hàm mật độ”, Tạp chí khoa học – Trường Đại học Tây Nguyên, số 45, Tr 13-19 Nguyễn Thị Thu Hà, Phạm Thị Bé, Phùng Thị Lan, Nguyễn Thị Mơ, Lê Minh Cầm Nguyễn Ngọc Hà (2021), “Whether planar or corrugated graphitic carbon nitride combined with titanium dioxide exhibits better photocatalytic performance?”, RSC Advances, https://doi.org/10.1039/D1RA01237A (Q1, SCIE, IF = 3.240) Nguyễn Thị Thu Hà, Phạm Thị Bé Nguyễn Ngọc Hà (2021), “Adsorption of lindane (g-hexachlorocyclohexane) on nickel modified graphitic carbon nitride: a theoretical study”, RSC Advances, https://doi.org/10.1039/D1RA03797H (Q1, SCIE, IF = 4.046) Phạm Thị Bé, Nguyễn Thị Thu Hà Nguyễn Ngọc Hà (2021), “Nghiên cứu lý thuyết khả hấp phụ Dichlorodiphenyltrichloroethane (DDT) Graphitic carbon nitride (g-C3N4) g-C3N4 biến tính cluster Ni2”, Tạp chí Xúc tác Hấp phụ, T10(3), Tr 106-111 Nguyễn Thúy Hằng, Phạm Thị Bé, Nguyễn Thị Kim Giang, Nguyễn Hoàng Hào, Nguyễn Hồng Anh Nguyễn Thị Thu Hà (2021), “nghiên cứu lý thuyết khả hấp phụ 2,4-dichlorophenoxylacetic carbon hoạt tính biến tính Fe Ag”, Tạp chí Khoa học Công nghệ B, T63(11DB), Tr 02-06 Phạm Thị Bé, Nguyễn Thị Thu Hà Nguyễn Ngọc Hà (2021), “Nghiên cứu lý thuyết khả hấp phụ Dichlorodiphenyltrichloroethane Graphitic Carbon Nitride biến tính sắt phương pháp phiếm hàm mật độ”, Tạp chí khoa học – Trường Đại học Tây Nguyên, số 51, Tr 60-66 Phạm Thị Bé, Nguyễn Hoàng Hào, Nguyễn Thị Kim Giang, Nguyễn Thị Thu Hà Nguyễn Ngọc Hà (2022), “Theoretical insight into the adsorption of dichlorodiphenyltrichloroethane on titanium dioxide supported on graphitic carbon nitride”, Russian Journal of Physical Chemistry A: Focus on Chemistry, DOI: 10.1134/S0036024422100065 (Q4, SCIE, IF = 0.697) Phạm Thị Bé, Bùi Cơng Trình, Nguyễn Văn Thức, Nguyễn Ngọc Hà Nguyễn Thị Thu Hà (2022), “Electronic and optical properties of metal decorated graphitic carbon nitride M/g-C3N4 (M = K, Ca, Ga, Ni, Cu): a theoretical study’, Tạp chí Hóa học (review) INTRODUCTION The reason for choosing topic Environmental pollution caused by chemical agents is always a news issue, urgent and receives the attention of the whole society Vietnam is an agricultural country with a very large area of rice and cash crops, which means regular use of pesticides and growth stimulants In addition, in many provinces and cities in our country, there are many storages of pesticides that have been seriously degraded The drainage system at the warehouses is almost nonexistent, so when heavy rains form a surface stream that washes away residual pesticides, polluting groundwater, surface water and soil pollution on a large scale Among the pesticides belonging to the POPs group, dichlorodiphenyltrichloroethane (DDT) and hexachlorocyclohexane (HCH) have been widely used in agricultural production in our country as well as in many other countries around the world Residues of the these substances in soil and water are still very high and therefore need to be treated Among the methods used to treat POPs, advanced oxidation process using photocatalyst systems is receiving the attention of scientists For the reasons mentioned above, we select the research problem: Study on the ability to process DDT and γ-HCH on some metals and metal oxides carried on g-C3N4 by the density functional tight binding methods Research objective and tasks a Research objective The objective of this study is use computational chemistry methodsto study the structute, electronic properties and optical properties of g-C3N4 based photocatalysts; g-C3N4 modified by metals: Me/g-C3N4 (Me = K, Ca, Ga, Fe, Ni Cu); g-C3N4 modified by metal oxide MexOy/g-C3N4 (MexOy = ZnO TiO2); study the ability of adsorption, decomposition and metabolism of some pesticides belonging to the POPs group (DDT and HCH) on these material systems; clarify the nature of the interaction between POPs with metal centers, catalytic metal oxides; predict reaction directions, preferred reaction products Thereby contributing to the direction of the experiment to synthesize highly effective materials in POPs treatment b Research tasks - Researching domestic and foreign documents, analyzing and reviewing published research works closely related to the thesis topic, presenting outstanding issues, thereby pointing out the issues that the thesis should focus on solving research; - Studying the theorytical basis of computational chemical methods in thesis (density functional method GFN2-xTB, CREST method, RP transition state determination method, dynamic method MD) - Studying the geometric structure, electronic properties and optical properties of g-C3N4; g-C3N4 modified by metals: Me/g-C3N4 (Me = K, Ca, Ga, Fe, Ni Cu); g-C3N4 modified by metal oxide MexOy/g-C3N4 (MexOy = ZnO TiO2); - Study the adsorption capacity of DDT and HCH on g-C3N4, Me/gC3N4 (Me = Fe, Ni) and TiO2/g-C3N4 - Study on the degradability of DDT and HCH decomposition under photocatalytic effect Scope and object of the study a Research object Research focuses on materials systems based on g-C3N4: g-C3N4 modified by some metals and: g-C3N4 modified by some metals oxides; and POPs pesticides include: DDT and HCH b Research Scope Study to clarify the molecular nature of interactions between metal atoms, semiconductor oxide cluster with g-C3N4, to clarify the influence of g-C3N4 modification on electronic and optical properties And the adsorption and degradability of this photocatalyst for pesticides belonging to the POPs group (DDT, HCH) Scientific and practical significance of the thesis a Scientific significance of the thesis Theoretical calculations used in the thesis will provide necessary information at the molecular level on the nature of interactions between metals, semiconductor oxides and g-C3N4, electron structure of material systems On the basic of g-C3N4, predicting optical properties such as band gap value, UV-Vis spectra, of Me, MexOy systems carried on g-C3N4 From there, predict and explain the adsorption and hotocatalytic degradation of DDT and HCH of these material systems The obtained results can be useful references for scientist, graduate student in the field of adsorptioncatalysis, computational chemistry b Practical significance of the thesis Due to the toxic nature, persistent in the environment, difficult to biodegrade and chemically and especially dangerous to human health of DDT and HCH, the study of material systems to decompose these substances is very important This has important practical significance Besides, with Vietnam participation in the Stockholm Convention and in the context of widespread use of pesticides in our country, the problem of handling POPs pesticides should be studied The obtained results can provide useful information in the development of adsorption-photocatalytic technology to treat organic pesticides in the form of POPs New points of the thesis - The geometrical structures, electronic and optical properties of graphitic carbon nitride (g-C3N4) in corrugated (cGN) and planar forms (pGN); gC3N4 doped with metals (K, Ca, Ga, Fe, Ni, Cu), and g-C3N4 combined with semiconductor oxides (ZnO)3, (TiO2)7 were studied; - The interaction energy, and electronic properties (ionization energy – IP, electron affinity – EA, global electrophilic index – GEI, fractional occupied density – FOD, … ) of the studied systems were calculated for clarifying the influence of the inclusion of metal atoms and metal oxides on the structure and properties of g-C3N4; - It has been predicted that Fe/g-C3N4, Ni/g-C3N4, and TiO2/g-C3N4 have the potential to be used as photocatalysts for the decomposition of DDT and HCH; - The adsorption of DDT and HCH on Fe/g-C3N4, Ni/g-C3N4, and TiO2/gC3N4 was studied in detail The preferred adsorption sites, the structural parameters of the adsorption configurations, the adsorption energy, as well as population analysis were determined to figure out the nature of the adsorption process It has been shown that the adsorption of DDT and HCH on modified g-C3N4 material systems is chemical in nature, while the adsorption process on primitive g-C3N4 is physisorption The influence of different solvents (water solvent, ethanol, acetonitrile, and benzene) on the adsorption process has also been studied; - The thermal stability of the DDT, HCH adsorption configurations was evaluated utilizing molecular dynamics method; - A new mechanism for DDT and HCH decomposition has been proposed This mechanism proposes receiving electrons directly from photocatalyst causes decomposition of DDT, HCH through cleavage of C - Cl bonds The layout of the thesis Introducing the reasons for choosing the topic, the purpose, and scope of the research, the new points of the thesis, the scientific and practical significance of the thesis Chapter 1: Introduce the theoretical basis including the problems of quantum chemical theory Chapter 2: Overview of the research system and method of calculation Chapter 3: Research results and discussion Conclusion: Briefly summarize the results of the thesis Chapter THEORY BASIS 1.1 Density functional theory DFT theory calculates electron correlations over electron density functions The DFT functions divide the electronenergy into parts that can each be calculated separately such as: kinetic energy, electron-nuclear interaction, Coulomb repulsion and some exchange correlations calculated for the corresponding part Remaining electron- electron interaction (which itself is divided into two separate parts, the exchange energy and the correlation energy) 1.2 GFN-xTB method GFN-xTB is a semi-empirical tight binding (TB) method for the calculation of structure, vibrational frequencies and noncovalent interactions of large molecular systems with 1000 or more atoms GFN indicates the design of the approach to yield reasonable geometries, vibrational Frequencies, and Noncovalent interactions, and “x” stands for extensions in the AO basic set and the form of the Hamiltonian In general, GFN-xTB provides for molecules from the whole periodic table higher accuracy for the target properties than existing ‘general-purpose’ semiempirical approaches It is applicable to a wider range of systems and is computationally and numerically more robust than other schemes with comparable accuracy 1.3 Moleculer Dynamic method (MD) Moleculer Dynamic method are used in chemistry, for example, for studies of the effect of tamperature on reactions, product stability with respect to temperature, time, … which cannot be calculated Directly from the results of solving the Schrödinger equation The MD method generally revolves around the use of Newton’s second law F = ma 1.4 Reaction path Estimates By default three runs with increasing push/pulling strengths -k = - × k1 at typical values of α = 0.5-1 are conducted Very tight optimization thresholds are applied in order to avoid trapping in spurious geometries The subsequent incomplete optimizations without the biasing potential at every point of the path (tylically 30 -200) are limited to 2-4 geometry optimizations steps such as a fall-back to the reactant/product is prevented It is recommended that the use checks the resulting path for chemical reliability 11 Table 3.1 The structural parameters of cGN pGN Calculated using the GFN2-xTB method Parameter cGN pGN pGN [116]* d(C-N2), Å 1,323 1,323 1,330 d(C-N1), Å 1,397 1,408 1,460 The structural parameters obtained by the GFN2-xTB method are very close to the results calculated according to the density functional theory for the studied system 3.1.2 Electron properties and optical properties of g-C3N4 Table 3.2 Parameters IP, EA and GEI of cGN pGN IP, eV EA, eV GEI, eV cGN 7,0856 2,2618 2,2641 pGN 6,6276 2,1531 2,1539 The IP and EA values of pGN are both lower thn that of cGN The GEI values of cGN and pGN are relatively high, and both indicate high electron acceptability of pGN as well as cGN Figure 3.3 HOMO LUMO of cGN depicted at an isovalue 0,03 e Å-3 12 Figure 3.4 HOMO LUMO of pGN depicted at an isovalue 0,03 e Å-3 Observing HOMO and LUMO images can lead to the conclusion that N2 atoms will be chemically more reactive than N1 atoms An effective photocatalyst is a material that satisfies the following two requirements: (1) the recombination rate of h+ and e* is low, (2) h+ and e* can be generated under visible light irradiation Starting from the first requirement, we propose three hypotheses for the explanation of an effective separation of h+ and e*: (1-a) The reduction and oxidation sites are located separately to facilitate photocatalytic reaction; (1-b) The greater the distance between h+ and e* is, the more efficient the separation is; (1-c) The electron density of HOMO (where h+ is formed) as well as LUMO (where e* is generated) in narrow space results in high densities of h+ and e*, which would be more effective for the electron transfer process Observing the HOMO and LUMO images of cGN and pGN in figure 3.3 and figure 3.4, the HOMO and LUMO of cGN and pGN are distributed in different spatial rigions and spread over many atoms, resulting in density photogenerated electrons and holes are quite small Hower, the photogenerated electron and hole are far apart resulting in efficient separation and slow recombination The same is true for pGN These 13 structural features, combined with moderate band gap energies, explain the photocatalytic activity of g-C3N4 Table 3.3 The parameters of the first excitation of g-C3N4 Excitation energy (eV) Oscillator strength The amplitude of MO transition f x 104 cGN 4,235 9,93 pGN 3,841 7,07 0,07 (H-4 0,06 (H-4 0,06 (H-1 L) L+3) L+1) 0,11 (H-1 0,08 (H 0,06 (H L+12) L+22) L+15) Figure 3.5 Molecular orbitals involved in the first excitation of cGN depicted at an isovalue 0,03 e Å-3 The MOs involved in the first excited states of cGN are distributed in a narrower space than that of pGN Athough the excitation energy in the first excited staten of cGN is large than that of pGN (4.235 eV and 3.841 eV) But, according to hypothesis (1-c) proposed above: The elecron density of H as well as L concentrated in the narrow region would be better, so cGN is predicted to have higher photocatalytic activity than pGN This result is completely consistent with previously published studies on the catalytic activities of cGN and pGN 14 Figure 3.6 Molecular orbitals involved in the first excitation of pGN depicted at an isovalue 0,03 e Å-3 cGN pGN Hình 3.7 FOD plots of cGN and pGN depicted at an isovalue 0,03 e Å-3 Observing the FOD images of cGN and pGN can once again confirm that the N2 atoms are more chemically active than the N1 aroms 3.2 MODIFIED g-C3N4 BY METALS (Me) AND CLUSTER OXIDE METALS (MexOy) 3.2.1 Modified g-C3N4 by metals Me (K, Ca, Ga, Fe, Ni and Cu) K/cGN (a) K/pGN (b) Ca/cGN (a) Ca/pGN (b) Figure 3.8 Optimized structure 15 Ga/cGN (a) Ga/pGN (b) Fe/cGN (a) Fe/pGN (b) Figure 3.9 Optimized structure Ni/cGN (a) Ni/pGN (b) Cu/cGN (a) Cu/pGN (b) Figure 3.10 Optimized structure Table 3.4 The calculated formation parameters of Me (K, Ca, Ga, Fe, Ni Cu) g-C3N4 Eint, Configuration (kJ dmin, Å mol-1) Total BO with N q(Me), BO atoms e Me/cGN K/cGN -209,4 2,588 0,330 0,101 + 0,627 Ca/cGN -366,3 2,703 1,594 0,752 + 0,480 16 Ga/cGN -460,9 2,188 1,338 1,078 +0,271 Fe/cGN -1178,3 1,873 2,620 1,414 +0,023 Ni/cGN -443,8 1,957 2,611 2,184 +0,444 Cu/cGN -383,3 1,904 1,506 1,251 +0,262 Me/pGN K/pGN -164,9 2,706 0,095