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As the world's second-largest alumina producer and the fourth-largest coal producer, Australia generates approximately 30 million tonnes of red mud (a byproduct of the Bayer process for alumina production) and 13 million tonnes of coal combustion products (fly ash and bottom ash) annually. While the recycling rate for coal combustion products in Australia is approximately 60%, the recycling rate for red mud (RM) is below 5%. This results in an increasing waste stockpile and poses a burden on the local environment. Therefore, there is a pressing need to find a sustainable solution for managing this expanding industrial waste stream. Geopolymer, as an alternative binder to traditional cement, offers improved sustainability due to its ability to utilize various industrial wastes as aluminosilicate precursors (APs). Extensive studies have predominantly verified the feasibility of using various types of industrial waste, including coal combustion products and RM, for geopolymer production. Therefore, the utilization of these local industrial byproducts in Australia for geopolymer production is becoming increasingly attractive, as it promotes both a circular economy and the valorisation of local industrial waste. The extreme variability in the inherent properties of these waste materials, however, including their chemical composition, particle size, and crystalline/amorphous phases, presents a significant obstacle to the wider application of geopolymer and hinders the valorisation of waste materials. To enable industrial-scale production, widely accepted standards for testing methods and material properties are crucial. These standards ensure the stability of the raw-material supply chain and the performance of the final product. [...], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Eng & Built Env, Science, Environment, Engineering and Technology, Full Text

Nanochannels with nanoscale characteristic dimensions have sparked broad interest across scientific and engineering disciplines. The emergence of a versatile family of two-dimensional (2D) materials enables high-throughput engineering of nanochannels with tunable layered structural and functional properties in the form of laminar membranes, which opens up new opportunities for applications in liquid molecular separation, gas separation, and ion sieving. Despite significant progress in 2D-material-based nanochannel, thorough understanding of this field is still lacking. In this thesis, I systematically and in-depth explored the mechanism of nanochannel modification on filtration. I also fabricated a series of 2D-material-based nanochannel membranes for water treatment. My research demonstrated that interlayer spacing plays a crucial role in determining the selectivity and permeability of nanofiltration membranes. Proper tuning gives these membranes high throughput, precise selectivity, and multiple uses. [...], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

Thiophene-based materials are some of the most versatile conjugated materials due to their combination of environmental stability and ease of synthetic modification. They are widely employed for photoelectronic applications, such as Organic Photovoltaics, however, thiophene-based materials in emissive applications fall far behind, possibly because of the limited fluorescent quantum yields in both solution and the solid state. Regardless of this limitation, thiophene-based materials still provide a number of characteristics that have made them popular systems for technological applications. In addition to the stability and synthetic diversity already discussed, these characteristics include controllable color tuning of absorption and emission, good charge mobility, and the ability to produce materials with low band gaps. The interest in emissive thiophene derivatives has also increased due to various approaches for overcoming the commonly reduced fluorescence efficiencies, as well as new applications such as fluorescent biomarkers. Besides the emissive properties, thiophene-based functional materials for photochromic systems are also studied intensively. Molecules in this category are usually termed "dithienylethene" concerning the structural motif of two thiophene rings bridged at their third position with an ethene group. Dithienylethenes (DTEs) outperform other photochromic systems in many ways, such as their excellent thermal stability in both isomers, high fatigue resistance, and switchability in the crystalline state. Before and after the irradiation, the two isomers differ not only in the absorption spectra but also in various physical and chemical properties, such as refractive indices, dielectric constants, oxidation-reduction potentials, and geometrical structures. The instant property changes without processing lead to their use in various optoelectronic devices, such as optical memory, photo-optical switching, display, and nonlinear optics. […], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), Institute for Glycomics, Full Text

Recent advancements in the domain of two-dimensional materials have taken a significant leap, with MXenes – a vibrant class of materials constituted of transition metals in conjunction with carbon, nitrogen or boron – gaining widespread attention from global scientific communities. Characterized by their atomic-level thickness, high aspect ratios, and superlative physicochemical attributes, MXenes exhibit immense potential within the realm of energy storage. Despite this potential, their practical application has been impeded due to the hazardous and costly nature of current mainstream MXene preparation methods, which involve the use of highly corrosive hydrofluoric acid. Moreover, challenges persist in the realm of high-rate performance, cycle stability, and environmental stability for pure phase MXenes, factors that are of paramount importance for commercial applications. Consequently, this research endeavors to develop environmentally friendly, cost-effective electrochemical methods conducive to MXene mass production, while also exploring MXene functionalization for superior performance in energy storage devices. [...], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

This thesis presents a novel approach to the electrochemical synthesis of functional nanomaterials, aimed at bolstering photocatalytic hydrogen production. The research encompasses a strategic manipulation of graphitic carbon nitride (g-C3N4), synthesis of iron oxyhydroxide (FeOOH) nanostructures, and the creation of a heterojunction nanostructure by coupling g-C3N4 with a two-dimensional MXene (Ti3C2). [...], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

Currently, the energy density of lithium ion batteries has reached a level of about 200 300 Wh kg-1, but the current energy density is still unable to meet the needs of long distance electric vehicles. In the future, the energy density of lithium ion batteries will need to continue to increase to more than 500 Wh kg-1 to meet the longer range and higher drive performance of electric vehicles. A lithium metal anode has the potential to increase the energy density and reduce the weight of batteries, making them more efficient and practical for use in electric vehicles and other applications. The advantages of lithium metal anodes include higher energy density, longer cycle life, and lower cost compared to other types of anodes. This is because lithium metal has a higher theoretical capacity (3860 mAh g-1) than graphite (372 mAh g-1), which is commonly used as an anode material in commercial lithium ion batteries. Additionally, the use of lithium metal anodes can reduce the weight of batteries and increase their energy efficiency, making them more practical for use in electric vehicles and portable electronic devices. However, there are still significant challenges that need to be overcome in order to fully realize the potential of lithium metal anodes. One major challenge is the formation of dendrites, which are branching structures that can grow from the surface of the lithium metal and cause short circuits within the battery. This can result in safety hazards and reduced cycle life. Another challenge is the issue of lithium metal oxidation and degradation during cycling, which can reduce the performance and cycle life of the battery. To overcome these challenges, researchers are exploring various strategies such as using protective coatings, designing new electrolytes, and optimizing the battery architecture. However, since there are so many factors affecting lithium dendrite generation, such as local current density, current density, flatness of lithium foil surfac, Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

Electro-catalyzed oxygen reactions, including ORR and OER, play a crucial role in future sustainable energy conversion, enabling a number of electrochemical devices (i.e., fuel cells, metal-air batteries, and water-splitting electrolyzers). The prerequisite for the practical application of these next-generation technologies is appropriate catalyst materials, which can accelerate reaction rate, decrease reaction overpotential, and enhance the selectivity toward the targeted reaction pathway. Nevertheless, the rational design and synthesis of electrocatalysts with favorable intrinsic characteristics are still challenging. Advanced design strategies and mechanism investigations are urgently needed to construct advanced materials for oxygen electrocatalysis. The combination of theoretical and experimental studies working in concert has proven to be a successful strategy in this respect, yielding a framework to understand catalytic trends that can ultimately provide rational guidance toward developing improved catalysts. This PhD thesis targets to rationally design and synthesize high-performance non-precious nano-electrocatalysts for oxygen electrocatalysis via theoretical and experimental means and explore their potential applications in electrochemical energy conversion.[…], Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text

The increasing concerns about environmental pollution, climate change, and the limited supply of fossil fuels have led to a growing demand for the development and distribution of renewable energy. Currently, lithium-ion batteries (LIBs) have gained dominance in the energy storage market, however, their further development is hindered due to limited natural resources and safety concerns, which calls for the search for low-cost and high-safety energy storage devices. Aqueous zinc ion batteries (AZIBs) have gained widespread attention due to their advantages of high safety, low cost, and high specific energy, in addition to abundant natural reserves and low cost of zinc metal. As such, AZIBs has emerged as promising candidate for the future development of electronics and electric vehicle and large-scale energy storage devices. The further practical application of AZIBs is highly restricted by Zn metal anode, since it suffers from uncontrolled dendritic and severe side reactions, including corrosion and hydrogen evolution reactions. The formation of dendrites can penetrate the separator, resulting in poor cycle life and strophic safety hazards. Regarding side reactions, the formation and accumulation of electronically insulating byproducts at the interface of the Zn anode would lead to an increase in interfacial resistance and polarization, thereby adversely affecting the reversibility of the Zn anode. And the occurrence of side reactions during battery cycling can result in volume expansion, which can negatively impact performance and cycle life. Here, this thesis presents viable solutions to the challenges mentioned above, which involve the electrolyte optimization and interface modification., Thesis (PhD Doctorate), Doctor of Philosophy (PhD), School of Environment and Sc, Science, Environment, Engineering and Technology, Full Text