Sustainable Nanocarbons for Energy Storage and Decarbonization

The excess exploitation and consumption of fossil fuel resources have led to severe energy crises and global warming, posing huge risks to human life. Tremendous efforts have been devoted to addressing these challenges by developing advanced energy storage systems and decarbonization methods. Lithium-sulfur (Li-S) battery is one of the most promising candidates for next-generation energy storage due to its high energy density. However, the “shuttle effect” of polysulfide leads to severe active materials loss and a limited lifespan of Li-S battery. Hence, feasible ideas that can suppress the polysulfide shuttle is highly desired for developing Li-S battery. On the other hand, natural gas leaks during the exploitation and use of natural gas drastically increased the concentration of methane (CH4) in the atmosphere. As known, methane is a type of greenhouse gas (GHG) with a much higher global warming potential than CO2. Therefore, it is necessary to detect natural gas leaks and reduce GHG emission.
Owing to impeccable properties, nanocarbons, including graphene and carbon nanotube (CNT), possess great potential to be applied to address the mentioned challenges, motivating researchers to explore methods for large-scale manufacturing of sustainable nanocarbons. Current nanocarbons manufacturing is limited by expensive and non-renewable raw materials, complex manufacturing processes, and low yield, which make nanocarbons expensive and unsustainable. Renewable biomass materials often have a high carbon percentile, rendering them to be promising raw materials for nanocarbons manufacturing. Moreover, their high reserve and low cost can significantly reduce the cost of nanocarbons. Nevertheless, the quality of biomass-derived nanocarbons is hard to control, which can hinder their application in industry.
This dissertation aims to develop new methods for deriving nanocarbons from biomass materials for energy storage and decarbonization. Specifically, Chapter 2 introduced a method to derive CNT from cotton via yeast catalysis. The obtained CNTs was demonstrated to suppress the shuttle effect in Li-S batteries. Subsequently, molecular dynamic (MD) simulations and density functional theory (DFT) calculations were used to unveil the mechanism behind cotton/yeast-derived CNTs’ polysulfide blocking effect, which helped to propose a design guideline for a CNT interlayer with optimized performance in Li-S batteries (Chapter 3). Apart from CNT, cotton has also been converted to graphene, where a hydrogen passivation method was applied to accelerate the mechanical exfoliation process of cotton-derived graphite and avoid the agglomeration of obtained graphene. Finally, the potential use of graphene and its derivatives in CH4 sensing was investigated. As a result, it was found that a combination of surface vacancies and hydroxyl groups could tremendously enhance graphene’ ability to selectively sense CH4 in complex environments containing air or water, enabling graphene derivatives to detect natural gas leaks.
Above all, the findings of this dissertation bring new insights into the commercialization of nanocarbons for energy storage and decarbonization, paving a new way toward sustainable development and carbon neutrality.