The electrochemical oxygen reduction reaction (ORR) is an essential half-reaction for the utilization of hydrogen as a sustainable fuel, via the conversion of hydrogen to electrons and protons... Show moreThe electrochemical oxygen reduction reaction (ORR) is an essential half-reaction for the utilization of hydrogen as a sustainable fuel, via the conversion of hydrogen to electrons and protons facilitated by the ORR. In the most common fuel cells, the ORR is requires high loadings of non-abundant platinum based catalysts. Inspired by Laccase, a multicopper oxidase able to perform the ORR at a low overpotential, copper complexes have become interesting targets as non-precious metal catalysts for the ORR.In this thesis, the ORR performance of molecular copper catalysts and the involved catalytic mechanisms have been investigated. The previously undetermined electrocatalytic mechanism for the ORR by the Cu(tmpa) copper complex was elucidated. Hydrogen peroxide was shown to play an important role in the catalytic cycle as a reaction intermediate. This has interesting implications for the sustainable electrochemical production of hydrogen peroxide. Furthermore, the reduction of hydrogen peroxide shows striking similarities with Fenton-like reactions observed in copper containing enzymes. Finally, the performance of several different copper electrocatalysts for the reduction of oxygen and hydrogen peroxide was investigated and compared. Show less
This thesis discusses the parameters affecting the catalysis for the electrochemical conversion of water into oxygen. The slow kinetics for the oxygen evolution reaction (OER) is one of the major... Show moreThis thesis discusses the parameters affecting the catalysis for the electrochemical conversion of water into oxygen. The slow kinetics for the oxygen evolution reaction (OER) is one of the major bottlenecks in the solar energy-to-fuels conversion process, which reduces the efficiency for the photo-electrochemical fuels generation (artificial photosynthesis). The work shows that to enhance the kinetics for the oxygen evolution reaction, one should not only look at the catalysts but also consider the synergy between catalyst and electrolyte. A more general approach that considers the electrochemical interface as a whole (electrode + electrolyte) is therefore the most promising route towards optimal activity. Show less
This thesis describes the results of the fundamental research on the electro-oxidation of ethanol. In addition, the oxidation of intermediates in the ethanol electro-oxidation reaction, such as... Show moreThis thesis describes the results of the fundamental research on the electro-oxidation of ethanol. In addition, the oxidation of intermediates in the ethanol electro-oxidation reaction, such as acetaldehyde and adsorbed CO, has also been studied. The goal of this research is to provide deeper insight into the molecular level understanding of the mechanism, and how various operational parameters affect this mechanism. With these insights, the development of low temperature direct ethanol fuel cells (DEFC) can be advanced, since, ultimately, the goal of fundamental catalysis research is the rational design of new catalysts, for which the understanding of molecular mechanisms is of essential importance. The mechanism of the electro-oxidation reaction is investigated using electrochemical techniques, such as cyclic voltammetry and chronoamperometry, as well as in situ characterization techniques, such as surface enhanced Raman spectroscopy (SERS), Fourier transform infrared spectroscopy (FTIR) and online electrochemical mass spectrometry (OLEMS). Show less
