Preparation of manganese oxide /graphene composites by plasma-enhanced electrochemical exfoliation process and its electrochemical performance

VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN THANH HAI PREPARATION OF MANGANESE DIOXIDE/GRAPHENE COMPOSITES BY PLASMA-ENHANCED ELECTROCHEMICAL EXFOLIATION PROCESS AND ITS ELECTROCHEMICAL PERFORMANCE MASTER’S THESIS Hanoi, 2019 VIETNAM NATIONAL UNIVERSITY, HANOI VIETNAM JAPAN UNIVERSITY NGUYEN THANH HAI PREPARATION OF MANGANESE DIOXIDE/GRAPHENE COMPOSITES BY PLASMA-ENHANCED ELECTROCHEMICAL EXFOLIATION PROCESS AND ITS ELECTROCHEMICAL PERFORMANCE Major: Nanotechnology Code: Pilot Research supervisor: Dr Phan Ngoc Hong MASTER’S THESIS Hanoi, 2019 i TABLE OF CONTENTS TITLE PAGE .i TABLE OF CONTENTS ii LIST OF FIGURES iv LIST OF TABLES vi LIST OF ABBREVIATIONS vii ACKNOWLEDGMENTS viii DECLARATION .ix ABSTRACT x INTRODUCTION Chapter OVERVIEW 1.1 Electrochemical energy storages 1.1.1 Supercapacitors 1.2 Electrode materials for supercapacitors 1.2.1 MnO2/graphene composites 1.2.1.1 Direct oxidation-reduction reaction 1.2.1.2 Solution-based mechanical mixing 10 1.2.1.3 The other methods 13 1.3 Current research in Vietnam 15 Chapter MATERIALS AND METHODS 18 2.1 Chemicals and reagents 18 2.2 Preparation of MnO2/graphene composites 18 2.3 Preparation of graphene and GM1 electrodes 19 2.4 Preparation of symmetric supercapacitor (GM1//GM1) 20 2.5 Characterizations 20 2.6 Electrochemical analysis 21 Chapter RESULTS AND DISCUSSION 23 3.1 Characterizations of MnO2/graphene composites 23 3.2 The proposed mechanism for PE3P method 29 3.3 Electrochemical performance 30 ii 3.4 Symmetric supercapacitor 35 CONCLUSIONS 39 LIST OF PUBLICATIONS 40 REFERENCES 42 iii LIST OF FIGURES Figure 1.1 A Ragone plot for various electrochemical energy storage devices [33] Figure 1.2 The working principles of (a) electrochemical double layer capacitor (carbon as the electrode material) and (b) Pseudocapacitor (MnO2 as the electrode material) in Na2SO4 electrolyte [18] Figure 1.3 (a) Schematic illustration for the synthesis of graphene–MnO2 composite (b) the comparison of specific capacitance with other materials [48] Figure 1.4 Schematic representations of the experimental design of MnO2/rGO composite [53] Figure 1.5 Schematic graphic of the synthesis process of the rGO/MnOx composite [41] 10 Figure 1.6 The formation mechanism for GO-MnO2 nanocomposites [2] 11 Figure 1.7 (a) Schematic representations for MnO2 anchoring on graphene through electrostatic attraction, (b,c) TEM image and (d) capacitance retention of MnO2/graphene [56] 12 Figure 1.8 Laser scribing of high-performance and flexible graphene/MnO2-based electrochemical capacitors [8] 13 Figure 1.9 (a) Schematic illustration for plasma-assisted electrochemical exfoliation method, (b) TEM image of graphene sheets and (c) XPS of C1s in graphene samples [37] 15 Figure 1.10 The detailed process of printing supercapacitor electrodes [7] 16 Figure 2.1 The schematic representation of the experimental design 19 Figure 3.1 SEM images of (a) graphene, (b) GM1 (1 mM KMnO4), (c) GM10 (10 mM KMnO4) and (d) MnO2 nanoparticles (1 mM KMnO4), respectively 23 Figure 3.2 EDX results of GM1 and their element mapping images 24 Figure 3.3 TEM images of (a) graphene and (b) GM1 25 Figure 3.4 Raman spectra of GM1 and graphene 25 Figure 3.5 XRD pattern of graphene and GM1 samples 27 Figure 3.6 XPS patterns of GM1, (a) survey, (b) C1s, (c) O1s and (d) Mn2p 28 Figure 3.7 Proposed mechanism for the formation of graphene/MnO2 composite 29 Figure 3.8 Cyclic voltammetry curves of (a) graphene and (b) GM1 electrodes in a M KOH electrolyte at a different scan rate of 5, 10, 20, 50, 100 mV s-1 31 iv Figure 3.9 Charge-discharge curves of (a) graphene and (b) GM1 electrodes in a M KOH electrolyte at a different current density of 2, 5, 10, 20 A g-1 32 Figure 3.10 Cycling performances of (a) GM1 and (b) graphene electrodes at a current density of 10 A g-1 34 Figure 3.11 (a) GCD curves of GM1//GM1 symmetric supercapacitor at a different current density of 2.5, 5, 10 A g-1 and (b) the specific capacitance of GM1//GM1 symmetric supercapacitor 36 Figure 3.12 Ragone plot of GM1//GM1 symmetric supercapacitor 37 Figure 3.13 Cycle stability of GM1/GM1 symmetric supercapacitor at a current density of A g-1 38 v LIST OF TABLES Table 3.1 Effect of concentration of KMnO4 on forming MnO2 nanoparticles 24 Table 3.2 The comparison of some vital parameters with other results 35 vi LIST OF ABBREVIATIONS CVD Chemical vapor deposition EDLC Electrochemical double layer capacitor GO Graphene oxide rGO Reduced graphene oxide SCs Supercapacitors CV Cyclic voltammetry GCD Galvanostatic charge/discharge SEM Scanning electron microscopy EDX Energy-dispersive X-ray TEM Transmittance electron microscopy XRD X-ray diffraction XPS X-ray photoelectron spectroscopy SCE Saturated calomel electrode PE3P Plasma-enhanced electrochemical exfoliation process CNTs Carbon nanotubes vii ACKNOWLEDGMENTS First of all, I would like to express my sincere gratitude to Dr Phan Ngoc Hong, Center for High Technology Development (HTD), Vietnam Academy of Science and Technology (VAST), for his extraordinary supervision, support and guidance throughout my research period My dissertation would not have been possibly conducted without his valuable advice and constructive comments I would like to express my appreciation to Assoc Prof Masashi Akabori, School of Materials Science, Japan Advanced Institute of Science and Technology (JAIST), for his excellent guidance, advice and support during the period of internship Especially Assoc Prof Masashi Akabori who has spent his precious time for training and helping me on characterizations and measurements I would strongly give my sincere appreciation to Dr Dang Van Thanh, who always support and encourage me during all my research and future academic careers His energetic and enthusiastic attitudes towards research inspire me to overcome the research challenges Additionally, I also acknowledge Dr Nguyen Tuan Hong for allowing me to use the facilities and providing the best conditions when I did experiments I also appreciate Mr Pham Trong Lam and Mr Dang Nhat Minh for their kind help and fruitful discussion about data analysis I also thank Mr Le Hoang for TEM measurements I would like to thank Nanotechnology Program staff, Ms Nguyen Thi Huong for being so nice and helping me with all the administrative and academic problems This thesis is supported by National Foundation for Science and Technology Development (NAFOSTED) under grant number 103.09-2017.360 Finally, special thanks go to my parents and my friends for being there, smiling at me with love, good days or bad days viii DECLARATION I hereby declare that all the result in this document has been obtained and presented in accordance with academic rules and ethical conduct I also declare that, as required by these rules and conduct, I have fully cited and referenced all material and results that are not original to this work Author Nguyen Thanh Hai ix Table 3.2 The comparison of some vital parameters with other results Maximum Material Electrolyte specific capacitance Cycle stability Ref (F g-1) MnO2/CNT Sponge@RGO@MnO2 Birnessite-type MnO2 MnO2/CNT graphene@NiO-MnO2 1M 199 F g-1 at 97% after 20 000 Na2SO4 0.1 A g-1 cycles 1M 205 F g-1 at > 90% after 3000 Na2SO4 0.1 A g-1 cycles 1M 191 F g-1 at Na2SO4 mV s-1 1M 167.5 F g-1 at >88% after 3000 Na2SO4 77 mA g-1 cycles 6M KOH 242.15 F g-1 at 0.2 mV s-1 - - [51] [11] [55] [4] [16] 180.0 F g-1 at > 99% after 1000 A g-1 cycles 1M 180.0 F g-1 at > 99% after 10 000 Na2SO4 mV s-1 cycles 1M 325.5 F g-1 at Na2SO4 0.3 A g-1 3D graphene/MnO2 1.5M 326.33 F g-1 92% after 1200 network Li2SO4 at 200 mV s-1 cycles 217.0 F g-1 at 80% after 3000 This A g-1 cycles work MnO2 nanowires 3D network b-MnO2 MnO2/CNT Graphene/MnO2 - 6M KOH - [17] [57] [14] [47] - : not available 3.4 Symmetric supercapacitor In order to investigate the excellent performances of graphene/MnO2 electrodes in practical applications, the symmetric supercapacitor has been fabricated by combining two graphene/MnO2 electrodes in parallel with KOH 6M electrolyte 35 Figure 3.11 (a) GCD curves of GM1//GM1 symmetric supercapacitor at a different current density of 2.5, 5, 10 A g-1 and (b) the specific capacitance of GM1//GM1 symmetric supercapacitor GCD tests were also examined with a potential range of 0–1 V at different current densities The charge and discharge curves were fairly symmetrical to each other, suggesting excellent reversibility and good charge propagation between them Furthermore, the specific capacitance of SC was determined by e.q (2.2) based on the discharge curves and was shown in Figure 3.11b The calculated specific capacitance could deliver up to 130.9 F g-1 at a current density of 2.5 A g-1 and 51.66 F g-1 at a current density of 10 A g-1 36 Figure 3.12 Ragone plot of GM1//GM1 symmetric supercapacitor The energy density and power density are two critical parameters in determining the property of supercapacitor Their relationship was presented in a Ragone plot Figure 3.12 represented the Ragone plot of GM1//GM1 symmetric supercapacitor and compared its E and P with those for other reported data of some typical MnO2 carbon-based supercapacitors The highest energy density of 18.18 Wh kg−1 at a power density of 2500 W kg−1 was achieved at a current density of 2.5 A g1 Furthermore, the energy density remained an acceptable value of 7.175 Wh kg−1 when increasing the power density up to 10 000 W kg−1, which are comparable with values reported in other publications [3, 12, 23, 32, 54] With high energy density, GM1 composites revealed to be an outstanding material for high-energy power supply components in electronic devices 37 Figure 3.13 Cycle stability of GM1/GM1 symmetric supercapacitor at a current density of A g-1 Similarly, the stability of symmetric supercapacitor is a crucial parameter in order to evaluate the lifetime and chemical stability of SC Thus, GCD tests were conducted to validate these characteristics The cycle stability of GM1/GM1 symmetric supercapacitor was displayed in Figure 3.13 In particular, the capacitance retention rates remained nearly 77% after over 3000 times of charging/discharging cycles During charge/discharge cycles, the rapid intercalation of K+ ions in electrode caused the mechanical expansion of MnO2, or the dissolution of some parts (graphene, MnO2) could lead to decrease the specific capacitance of the device Overall, SC exhibited an excellent cycle life and good stability 38 CONCLUSIONS In this study, we presented a simple, low-cost and one-step method to synthesize graphene/MnO2 composites via plasma-enhanced electrochemical exfoliation process and its electrochemical performance The morphologies, structures and chemical compositions of the obtained composites were characterized by SEM, EDX, TEM, XRD, Raman and XPS MnO2 nanoparticles distributed uniformly on graphene sheets in our composite with KMnO4 concentration and reaction time of mM and hour, respectively The cyclic voltammetry and galvanostatic charge/discharge measurements showed EDLC behavior for graphene and pseudocapacitive behavior for graphene/MnO2 composites According to CV results, the specific capacitance of graphene and GM1 was calculated and found to be about 119 and 48 F g-1 at mV s-1, respectively After 3000 cycles, the capacitance retention of graphene/MnO2 composite was remained at 80% of its initial value, indicating excellent electrochemical stability By symmetric configuration, the packing cell of graphene/MnO2 supercapacitor has been performed in a range of 0-1 V, and the energy density delivered up to 18.18 Wh kg−1, suggesting its potential for practical application The exceptional electrochemical performance could be assigned to the synergy effect of MnO2 nanoparticles and graphene nanosheets Thus, graphene/MnO2 composites possibly show a noticeable active material for practical application in high-performance and light-weight supercapacitors 39 LIST OF PUBLICATIONS Xuan Linh Ha, Thi Thu Ngo, Quoc Toan Tran, Tra Huong Do, Syamone Somxayasine, Huynh Ky Phuong Ha, Hong-Tham T Nguyen, Thi Kim Chung Nguyen, Tri Khoa Nguyen, Thanh Hai Nguyen, “Fast and effective route for removing of methylene blue from aqueous solution by using red mud-activated graphite composites”, submitted to Journal of Chemistry (accepted) Ha Xuan Son, Pham Van Hao, Hac Van Vinh, Nguyen Thanh Hai, Nguyen Thi Kim Ngan, Dang Nhat Minh, Phan Ngoc Minh, Phan Ngoc Hong, Dang Van Thanh, “Removal of arsenic from water using crumpled graphite oxide”, Green Processing and Synthesis, 2018, 7, 404-408 Chien Nguyen Van, Nguyen Thanh Hai, Jiri Olejnicek, Petra Ksirova, Michal Kohout, Michaela Dvorakova, Pham Van Hao, Phan Ngoc Hong, Manh Cuong Tran, Do Hoang Tung, Dang Van Thanh, “Preparation and photoelectrochemical performance of porous TiO2/graphene nanocomposite films”, Materials Letters, 2018, 213, 109–118 Lưu Việt Hùng, Nguyễn Thanh Hải, Nguyễn Thành Trung, Đỗ Trà Hương, Nguyễn Phương Chi, Nghiêm Thị Hương, Đặng Văn Thành “Hấp phụ Mn(II) môi trường nước sử dụng nano bentonit chế tạo phương pháp hoạt hóa có hỗ trợ siêu âm”, Tạp chí Hóa học, tập 56, số 3e, 2018, tr 27-32 Nguyen Thanh Hai, Ha Xuan Linh, Nguyen Thi Thuy, Nguyen Nhat Huy, Le Phuoc-Anh, Phung Thi Oanh and Dang Van Thanh, “Electrochemical activation of graphite using red mud slurry for enhancing electrochemical performances”, Vietnam- Japan Science and Technology Symposium 2019 (VJST2019), Ha Noi, Vietnam, May 4th 2019 Xuan Linh Ha, Thi Thu Ngo, Quoc Toan Tran, Tra Huong Do, Syamone Somxayasine, Huynh Ky Phuong Ha, Hong-Tham T Nguyen, Thi Kim Chung Nguyen, Tri Khoa Nguyen, Thanh Hai Nguyen, “Fast and effective route for removing of methylene blue from aqueous solution by using red mud-activated graphite composites”, International Conference On Advanced Nanomaterials For Green Growth, ADMAT 2019 Ha Noi, Vietnam, April 4-7 2019 40 Nguyen Thanh Hai, Dang Nhat Minh, Tran Viet Thu, Le Trong Lu, Nguyen Tuan Hong, Phan Ngoc Minh and Phan Ngoc Hong, “Preparation of MnO2/graphene composites by plasma-enhanced electrochemical exfoliation method and its electrochemical properties”, The 9th International Workshop on Advanced Materials Science and Nanotechnology, IWAMSN 2018 Ninh Binh, Vietnam, November 7-11 2018 Le Ngoc Trung, Dang Nhat Minh, Nguyen Ngoc Anh, Bui Thi Thanh Loan, Nguyen Thanh Hai, Do Nhat Minh, Le Trong Lu, Phan Ngoc Minh, Nguyen Tuan Hong, and Phan Ngoc Hong, “One-step synthesis of MoOx/graphene composites”, The 9th International Workshop on Advanced Materials Science Nanotechnology, IWAMSN 2018 Ninh Binh, Vietnam, November 7-11 2018 41 and REFERENCES [1] An, G., Yu, P., Xiao, M., Liu, Z., Miao, Z., Ding, K., & Mao, L (2008) Lowtemperature synthesis of Mn(3)O(4) nanoparticles loaded on multi-walled carbon nanotubes and their application in electrochemical capacitors Nanotechnology, 19(27), 275709 doi:10.1088/0957-4484/19/27/275709 [2] Chen, S., Zhu, J., Wu, X., Han, Q., & Wang, 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