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
Nitrate reduction on Sn-modified polycrystalline Pt has been investigated. NO is the main product at high Sn coverage, whereas N2O is dominant at low Sn coverage. The N2O reduction on Sn-modified... Show moreNitrate reduction on Sn-modified polycrystalline Pt has been investigated. NO is the main product at high Sn coverage, whereas N2O is dominant at low Sn coverage. The N2O reduction on Sn-modified Pt electrodes indicates electrochemical formation of N2 is related to pristine Pt sites. Moreover, homogeneous chemical reactions of intermediates products also contribute to N2O and N2 formation of in solution. The p-block metals have been studied: Cd, In and Sn show a promoting effect; Ga shows a limited enhancement; Tl shows a special promoting effect in sulfuric acid; Pb shows a weak formation of N2O. Density Functional Theory calculations show that Sn and In enhance nitrate adsorption compared with pristine Pt. Moreover, ammonia is found as the only product on Pt. After modification by Sn, hydroxylamine is specifically found with nitrite, which supports that nitrate reduction to nitrite is enhanced by Sn and Sn could steer the hydrogenation of NOads. However, solution pH is an important factor. On Pt, nitrate reduction is only observed in acidic solution. On Rh, a higher activity is observed in wide pH, which suggests a mechanism that HNO3 molecule is the active species. However, Rh additionally shows a special ability to reduce NO3- directly. Show less
