| Resumo: | In recent years the amount of CO2 release into the planet atmosphere has increase exponentially due to a global dependency in fossil fuels. This is one of the major contributors to the climate change that is seen nowadays. On the other hand, due to the CO2 abundance, there has been an interest in developing methods to harvest and use this CO2 in the production of green energy and sustainable chemistry. Formate dehydrogenase (FDH) proteins are a class of metalloenzymes with different subunit composition containing either molybdenum or tungsten at the active site. FDH catalyses the oxidation of formate into CO2. Recently it was shown that some of the FDH enzymes have the ability to perform the reverse reaction that is, these can catalyse the reversible interconversion of CO2 and formate. However, to date, the electrochemical characterisation of the protein has not yet been attained using direct, non-mediated methods. In this thesis the isolation of FDH from Desulfovibrio desulfuricans, its biochemical and non-mediated electrochemical characterisation was attained. The redox features of the Mo catalytic centre of the enzyme, including thermodynamic and kinetic parameters such as its formal reduction potential (E0’ = -245 ± 8 mV vs NHE) and heterogeneous electron transfer constant, were determined, for the first time, using direct electrochemical methods. The catalytic activity towards the CO2 reduction was also observed, for the first time, by direct electrochemical techniques.
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