CO2 photoreduction at enzyme-modified metal oxide nanoparticles

A model system for photoreduction of CO2 to CO using visible light has been extensively studied, using a catalyst for which the CO2/CO reaction is electrochemically reversible. The hybrid system comprises metal oxide nanoparticles functionalised with the enzyme carbon monoxide dehydrogenase (CODH), and sensitised to visible light using a ruthenium bipyridyl photosensitiser. An anatase/rutile TiO2 mixture (Evonik Degussa P25) was selected as the most suitable semiconductor, and CO production rates and stability were examined as a function of each component (photosensitiser, enzyme and TiO2). Tolerance to O-2 and effects of different electron donors were also investigated, together with strategies to control enzyme binding at the surface of TiO2 in order to enhance overall activity.