Application of carbon based materials in hybrid energy storage and harvesting systems

In a world that is actively trying to reach a more sustainable future, energy storage represents the challenge of the present. As renewable sources are not continuous (in the sense that their availability is affected by factors such as weather and time of day), and energy harvesting devices become more and more efficient, the need for a reliable storage system is critical. In this work, the focus is directed towards the long-term viability of energy storage units, which should encompass environmental impact of manufacturing processes, cyclability and end-of-life disposal. A strong effort is put in designing an hybrid device combining strong power capabilities with high energy density. This is done by exploiting a supercapacitor's (SC) double layer charge mechanism coupled with reversible faradaic reactions from a battery-like electrode. The final goal of the project is to connect the SC to an appropriately sized dye-sensitized solar cell (DSSC), so that their combined operation can drive low-power sensors and devices in a charge/discharge cycle alternating between day and night. The whole system would therefore be self-sustaining and low maintenance thanks to the reversibility of the charge and discharge processes. To ensure environmental friendliness, the choice of materials includes low-cost and widely available compounds, such as carbon-based substances and lithium manganese oxide, the latter being a strong alternative to lithium cobalt oxide, which has dominated the battery market but raises sustainability concerns due to limited availability, environmental impact from mining, and recycling challenges. The carbon-based source in this case comes from agricultural waste, in the form of rice husk (RH), which has already exploited as a source of silica in literature. The RH has been transformed in a 4-step procedure into carbon aerogel, which provides the porous structure yielding the high surface-to-volume ratio needed to reach a considerable capacitance. All in all, the final device aims to be a significant step towards achieving net zero carbon emissions by integrating sustainable materials and advanced energy storage technologies. With the combination of SCs and DSSCs, this approach hopefully contributes to a more sustainable future and sets a precedent for new developments in eco-friendly energy storage systems.