Molecular Water Oxidation Catalysts Based on Copper and Nickel Complexes

Identifier:  TDX:2889

Handle: https://hdl.handle.net/20.500.11797/TDX2889

Authors:  Garrido Barros, Pablo

Abstract:
This Doctoral Thesis focuses on the study of molecular catalysts for water oxidation based on copper and nickel since their high abundance and inexpensive character make them potential candidates for their use in catalytic systems. Despite that, there is a current lack of information regarding their reaction mechanism and the factors that determine their activity. Therefore, we first develop new molecular catalysts based on copper as metal center. Their mechanistic study reveals the essential role that the ligand oxidation has in the catalytic cycle as tool to control the reaction overpotential. In collaboration with Prof. Maseras group (ICIQ) a new mechanism for the oxygen-oxygen bond formation is found to operate in different copper catalysts. This unprecedented mechanism allows us to redefine the mechanistic scenario in water oxidation. Later on, the design of new ligands with different redox properties is addressed. That allows to study the factors that have influence on the activity and reaction mechanism and provide valuable information for the design of more active, stable and efficient new catalysts. Moreover, the immobilization of the molecular catalyst on the surface of graphene-based electrodes is also studied. We discover the essential role of the π-delocalization in increasing the reaction kinetic by more than two orders of magnitude. Finally, the knowledge developed with copper complexes is applied in nickel catalysis. This allows to study the labile character of nickel complexes in basic media that determine the presence of two different operating mechanism based on molecular species and nickel oxides respectively.