Photoelectrochemical biomass valorisation for renewable energy conversion

Natural Photosynthesis has become a guiding model for developing sustainable solutions aiding in the transition from fossil fuels to renewable energy sources. For over a century, scientists have sought to mimic plants by creating devices capable of capturing energy and storing it in chemical bonds. Among the approaches explored to date, splitting water into molecular hydrogen and oxygen offers a promising breakthrough for clean energy production. However, the slow kinetics of the oxygen evolution reaction (OER) consistently hampers the efficiency of this process, limiting its competitiveness against widely available fossil-based technologies. To overcome this limitation, the focus of the scientific community is shifting towards alternative oxidation reactions, characterised by lower energy requirements and inexpensive starting compounds. In this thesis, the photoelectrochemical conversion of biomass derivatives to useful chemicals is investigated. The following anodic reactions were explored: i) Titanium doped hematite (Ti:Fe2O3) photoanodes modified with cobalt- or nickel-based co-catalysts, for the conversion of 5-hydroxymethylfurfural (HMF) into 2,5- furan dicarboxylic acid (FDCA); ii) bismuth vanadate (BiVO4) photoanodes for glycerol oxidation reaction (GOR). Overall, a comprehensive understanding of the optimal conditions for both reaction and photoanode stability was crucial for maximizing process performance. This knowledge can also pave the way for successfully coupling valuable cathodic reaction, such as the hydrogen evolution reaction (HER) or CO2 reduction, thereby greatly enhancing the overall functionality and effectiveness of the PEC device.