Artificial photosynthesis (AP) is one of the scientific challenges that could help us achieving a global “carbon neutral” society. Photocatalytic water splitting is considered as the first... Show moreArtificial photosynthesis (AP) is one of the scientific challenges that could help us achieving a global “carbon neutral” society. Photocatalytic water splitting is considered as the first challenge of AP, which contains two half reactions: water oxidation and hydrogen evolution. It is widely accepted that a photocatalytic system needs a minimum of three components: a photosensitizer (PS), a catalyst (Cat) and a sacrificial electron donor or acceptor (SE). In such a photocatalytic system, at least three electron-transfer steps can be identified: one between the SE and the excited PS (PS*), one between the photo-reduced or photo-oxidized PS and the Cat, and one between the Cat and its substrate. This thesis on the one hand focused on developing improved molecular components for the two half reactions of water splitting in purely homogeneous systems. On the other hand optimized photocatalytic systems with balances between the driving force of electron transfer from the SE to the PS*, and that of electron transfer between the catalyst and the oxidized or reduced photosensitizer (PS+ or PS–). Show less
Electrocatalysis allows for storing electricity or converting it into chemical bonds, producing chemical building blocks and fuels using renewable resources. Therefore, it plays an important role... Show moreElectrocatalysis allows for storing electricity or converting it into chemical bonds, producing chemical building blocks and fuels using renewable resources. Therefore, it plays an important role in the transition towards a more sustainable future for our society through electrification. Still, to bring electrochemical technologies to industrial scale and make them competitive, optimization of various aspects of electrocatalytic reactions are needed. Many fundamental studies focus on understanding the catalyst surface, however, different components of the electrolyte, as pH and cations, have also shown to significantly affect the reaction activity and selectivity. In view of that, in this thesis, various aspects of the electrode-electrolyte interface are studied at different scales, using Scanning Electrochemical Microscopy (SECM), stationary and rotating-disc electrode voltammetry techniques, and bulk electrolysis. Show less
