Band Gap Engineering of Zinc Cadmium Sulfide for Solar Driven Lignin Depolymerization
Date
2022-08
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Abstract
Biomass photorefinery for simultaneous production of value-added chemicals and sustainable hydrogen holds a promising perspective for achieving a negative carbon economy scenario. However, an insight into the light-driven lignin depolymerization approach is still lacking due to the highly complex structure and constitution. Lignin corresponds to 15-30% of biomass weight and is the major renewable source of aromatics in nature, and still, most of it is used as low-grade solid fuel. This work aimed to address this challenge by designing a series of Zn1-xCdxS solid solutions photocatalysts to study the depolymerization mechanism of lignin model compounds. Bandgap engineering strategy was used by changing the Zn/Cd ratio, which is a proven method to regulate the reaction pathway. Specifically, Zn0.5Cd0.5S (ZCS50) demonstrated the best substrate conversion to mono phenolic compounds achieving 27% conversion in 2 hours. It was also observed that different reaction pathways could occur depending on the photocatalyst's band structure, which directly affected product distribution. For instance, the application of Zn0.75Cd0.25S (ZCS25) led to the highest hydrogen yield, which is considered a side product with large importance for biorefineries, however it presented low overall depolymerization of lignin. Finally, the photocatalyst with better performance, ZCS50, was applied in the conversion of two different types of lignin to demonstrate its applicability. After 16h reaction, a wide range of monomeric aromatics were detected as products with simultaneous H2 production, but a low conversion was observed. Nevertheless, the present study could demonstrate excellent examples of biomass valorization by fine designing photocatalysts with room for future optimization.
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Keywords
lignin, photocatalysis
Citation
Goes Palma, B. (2022). Band gap engineering of zinc cadmium sulfide for solar driven lignin depolymerization (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.