Abstract

With rising global energy demands, fossil fuels are being consumed at their quickest rate yet. Overconsumption, unsustainable practices and environmental concerns have accelerated the search for alternative, renewable and environmentally friendly energy sources. One such promising source is biodiesel, which is formed through the transesterification of refined vegetable oils in the presence of methanol and a homogeneous catalyst such as sodium/potassium hydroxide. While the reaction is efficient, limitations associated with tedious purification coupled with the inability to reuse the catalyst have limited its global production and adoption. A variety of heterogeneous catalysts have been investigated as catalytically efficient alternatives yet their preparation often entails tedious synthetic procedures or the use of heavy metals, which can lead to metal leaching and increased purification costs. It is in this regard that carbon dots, a new member of the carbon nanomaterial family, has been be explored as a potential metal-free alternative. Carbon dots offer several advantages namely cost effective and facile preparation from accessible and sustainable precursors coupled with a tunable surface chemistry. In this work, carbon dots derived from glycine were synthesized using microwave and hydrothermal techniques. Their physico-chemical properties were characterized and their catalytic efficiency towards the transesterification reaction of canola oil was investigated resulting in biodiesel conversions > 95%. We investigated the mechanism of catalysis and we exploited our findings to design a carbon dot catalyst from precursors such as lignin and glycerol, the principle waste product of the biodiesel reaction. By rendering the production process cost effective and energetically favorable, while maintaining sustainable practices, biodiesel global adoption can increase and global energy demands may be met in an energy efficient, sustainable and financially feasible manner.