- Title
- Functional borocarbonitrides for CO2 capture and energy storage
- Creator
- Bahadur, Rohan
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2023
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Huge technological advancements and rapid climate change have brought major issues including energy scarcity, increased heat and drought and rising sea levels. Therefore, the incentive to develop technologies to overcome some of the challenges is critical and requires urgent attention. The requirement materialises from the exhaustive nature of fossil fuels and the concerns arising from global warming. The development of novel energy storage technologies has seen a constant effort from researchers worldwide and this has constantly been evolving with a requirement for more efficient devices. The current market requires a wide variety of such devices demanding specific properties for their individualistic purposes. While some devices, such as electric vehicles, might require a larger energy density, portable electronics might require a higher power density. However, each material developed comes with its own set of drawbacks and therefore, newer materials are constantly being explored. Among these devices, particular attention has been given to Li-ion batteries (LIBs) and supercapacitors. LIBs have always been at the forefront of this ever since Sony commercialised the first LIB in 1991. However, recently it got a huge resurgence due to the advent of electric vehicles. Supercapacitor has a similar design, however, differs in terms of functionality and serves their own purpose in the field of energy storage. Among the same class but less explored are sodium-ion batteries, which are more abundant and cheaper than their Li+ counterparts. They, however, have lower energy density due to the larger size of Na+, but there is a huge scope for improvement with the advancements in high-performance electrode materials. Borocarbonitride (BCN / BxCyNz) forms an interface between BN and graphene. It can be finely tuned to possess properties shown by the two materials based on the stoichiometric ratio of the two elements. B (p-doped) and N (n-doped) doping in the carbon matrix increases the charge migration on the surface by providing active sites and creating vacancies which help in charge storage in batteries. By inducing porosity in these structures, certain properties such as surface area, pore volume, and pore diameter can be manipulated. These porous channels are extremely important as they assist in ion migration and are able to store more charge than their non-porous counterparts. In the thesis, different configurations of porous BCN have been explored for solving key energy-related issues. They are synthesised using different approaches, and the high surface area and unique porosity have been effectively manipulated using basic experimental parameters. The synthesised materials were characterised to analyse their structure-property relationship. The crucial parameters associated with the energy application have been investigated in depth. The thesis is broadly divided into three sections. The first chapter encompasses a literature review of the structure and chemical properties of BCN, their synthesis methods, and its multiple applications. The different synthesis methods, such as pyrolysis, chemical vapor deposition, elemental substitution reaction, and functionalisation strategies for making these unique materials, are discussed. Critical analysis is carried out to understand the mechanism and changes behind some of the properties which arise in the multi-elemental compound comprising of B, C, and N as the pores are introduced in the structure. Following which, applications such as energy storage, photocatalysis, adsorption, biomedical, gas capture, for these exciting novel materials are discussed. Chapter two discusses the use of BCN conjugated in high surface area carbon synthesised through the simple approach of chemical activation. The obtained materials were fine tuned to obtain the optimum surface area and pore volume. The materials were characterised using various tools to understand the structural and chemical evolution by modifying the nitrogen precursor. It is observed that the precursor plays an important role in not just modifying the chemical structure but also the textural parameters, which is majorly instigated through the use of potassium acetate as the activating agent. Potassium acetate is less corrosive compared to conventional activating agents such as KOH, and ZnCl2. However, the surface area achieved is comparable and even higher than some of the reported literature. This might be achieved due to the use of a high nitrogen-containing precursor, facilitating the activation procedure. The carbon source utilised herein is a biomass source, which greatly reduces the overall cost of the synthesis. These materials showed exceptional performance as supercapacitor electrodes and CO2 adsorbents, due to their unique porous characteristics and multi-elemental surface. In chapter three, we delve into the ordered mesoporous BCN derived from the 3D KIT-6 silica hybridised with the 0D fullerene structure. The method of hard templating using KIT-6 provides an ordered porous structure and the use of the 0D structure of fullerene provides a heterojunction at the interface, which assists in the intermolecular electron transfer. This coupled with the heteroatoms on the BCN structure, makes it particularly exciting for supercapacitors and batteries. The high surface area provides an ample amount of channels for ion exchange which assists in increasing the energy density, whereas, the ordered mesopores assist in managing the strain relaxation during the charge and discharge process. The obtained mesoporous BCN-C60 composites were used as anodes in LIBs and as electrodes in supercapacitors and the abovementioned properties assisted in providing excellent performance in both applications. Due to the non-metallic nature of the materials, these materials exhibited exceptional stability as well in both cases. In the conclusions, the outcomes from the studies have been briefly described. It is important to note that while surface area plays a vital role in governing some of the application performance of these materials, the careful tuning of the ternary compound can lead to many exciting properties. Further, some of the future prospects and the immense scope of porous BCN have been explained.
- Subject
- borocarbonitrides; carbon-based material; energy Storage; gas capture; supercapacitors; lithium ion batteries; thesis by publication
- Identifier
- http://hdl.handle.net/1959.13/1510594
- Identifier
- uon:56432
- Rights
- Copyright 2023 Rohan Bahadur
- Language
- eng
- Full Text
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