2D materials and conjugated small molecules: from synthesis to devices for energy applications
Doctoral thesis, 2021
The main goal of the present work is to contribute to the area of renewable energy storage, through the precise engineering of 2D materials and conjugated materials. Thus, four different types of graphene-based materials and a conjugated small molecule were synthesized in order to successfully develop supercapacitors. In the case of graphene-based materials, it was possible to modify its main parameters such as lateral dimensions, dispersibility, and energy levels.
Furthermore, a new graphene-based material (SOG), that combines the advantages of GO and graphene without their disadvantages, was synthesized. SOG shows water dispersibility, a C/O ratio 260% higher than GO, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414. The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, which is 75 times lower compared to GO. Moreover, the electrical resistance is nine orders of magnitude smaller (1.12 KΩ/sq) compared to GO. In order to analyze the feasibility of SOG for energy storage application, a swagelok-based supercapacitor was fabricated which exhibited remarkable characteristics such as 16 474 mF g-1 of gravimetric capacitance, and good retention at 10 000 mV s-1 of scan rate. SOG characteristics make it a promising new material for applications in organic electronics.
Finally, a novel perylene diimide-based (PDI) and indacenodithieno[3,2-b]thiophene (IDTT) small molecule has been successfully synthesized and used for the first time as an organic-electrode supercapacitor. This new approach circumvents complex issues regarding the synthesis and purification of polymers. Promising results of a nanocomposite made of this SM and 10% SOG demonstrate a synergistic effect of 48.75% increase in the capacitance at 10 mA g-1, in two-electrode cells for a practical demonstration in energy storage. This study may open new possibilities for fabricating supercapacitors and multifunctional devices from conjugated small molecules and graphene-based materials.
Furthermore, a new graphene-based material (SOG), that combines the advantages of GO and graphene without their disadvantages, was synthesized. SOG shows water dispersibility, a C/O ratio 260% higher than GO, and most importantly, a very high crystallinity degree, with an ID/IG of 0.414. The synthesized SOG exhibits an ultra-low optical band gap of 0.04 eV, which is 75 times lower compared to GO. Moreover, the electrical resistance is nine orders of magnitude smaller (1.12 KΩ/sq) compared to GO. In order to analyze the feasibility of SOG for energy storage application, a swagelok-based supercapacitor was fabricated which exhibited remarkable characteristics such as 16 474 mF g-1 of gravimetric capacitance, and good retention at 10 000 mV s-1 of scan rate. SOG characteristics make it a promising new material for applications in organic electronics.
Finally, a novel perylene diimide-based (PDI) and indacenodithieno[3,2-b]thiophene (IDTT) small molecule has been successfully synthesized and used for the first time as an organic-electrode supercapacitor. This new approach circumvents complex issues regarding the synthesis and purification of polymers. Promising results of a nanocomposite made of this SM and 10% SOG demonstrate a synergistic effect of 48.75% increase in the capacitance at 10 mA g-1, in two-electrode cells for a practical demonstration in energy storage. This study may open new possibilities for fabricating supercapacitors and multifunctional devices from conjugated small molecules and graphene-based materials.
conjugated materials
graphene-based materials
energy storage
solution processing
10-an, Kemigården 4, Chalmers
Opponent: Professor Zdenek Sofer, University of Chemistry and Technology Prague, Czech.
Author
Ulises Mendez Romero
Chalmers, Chemistry and Chemical Engineering, Applied Chemistry
Tiny materials for huge energy storage
Two-dimensional (2D) materials, like graphene-based materials, are essentially single atomic layers of ordinary graphite used in the pencil's tip; they are so thin that they are not considered as 3D materials. As you might know, graphite, charcoal, and diamond are the same type of materials in terms of chemical element, but just different in atomic arrangement. 2D materials have very different and unique properties as compared to their counterparts, which grant them quite many interesting potential applications. On the other hand, conjugated small molecules (SM) are synthetic materials like the plastics around us but with fascinating electric properties like semiconductor. Conventional semiconductors like silicon are fragile, stiff, and expensive to produce and process. On the contrary, SM are solution-processable and can be easily produced and modified for target applications.
For a sustainable society, the supply of cheap and green energy is indispensable. Since renewable energy sources are often intermittent, it is crucial to store the produced energy. Supercapacitors are excellent candidates with numerous advantages: high-power density, ultra-fast charge-discharge, and long cycle life. However, the low energy density remains as its main drawback. In this thesis, through the proper modification of 2D materials and a conjugated small molecule, it was possible to increase by almost 50% energy density of the supercapacitors by a synergistic combination of these type of materials.
Two-dimensional (2D) materials, like graphene-based materials, are essentially single atomic layers of ordinary graphite used in the pencil's tip; they are so thin that they are not considered as 3D materials. As you might know, graphite, charcoal, and diamond are the same type of materials in terms of chemical element, but just different in atomic arrangement. 2D materials have very different and unique properties as compared to their counterparts, which grant them quite many interesting potential applications. On the other hand, conjugated small molecules (SM) are synthetic materials like the plastics around us but with fascinating electric properties like semiconductor. Conventional semiconductors like silicon are fragile, stiff, and expensive to produce and process. On the contrary, SM are solution-processable and can be easily produced and modified for target applications.
For a sustainable society, the supply of cheap and green energy is indispensable. Since renewable energy sources are often intermittent, it is crucial to store the produced energy. Supercapacitors are excellent candidates with numerous advantages: high-power density, ultra-fast charge-discharge, and long cycle life. However, the low energy density remains as its main drawback. In this thesis, through the proper modification of 2D materials and a conjugated small molecule, it was possible to increase by almost 50% energy density of the supercapacitors by a synergistic combination of these type of materials.
Subject Categories
Chemical Sciences
ISBN
978-91-7905-597-4
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5064
Publisher
Chalmers
10-an, Kemigården 4, Chalmers
Opponent: Professor Zdenek Sofer, University of Chemistry and Technology Prague, Czech.