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- Resumen es exacto "Current environmental concerns have renewed the interest in the use of hydrogen as an energy carrier for automotive applications, through its electrochemical conversion in fuel cells. The main route for H2 production is the methane steam reforming reaction (MSR), followed by the water-gas shift reaction (WGS), which reduces the content of CO. However, these reactions are carried out industrially at very high temperature and pressure, resulting in elevated operating costs. The use of H2 as a fuel requires the development of novel catalysts capable of carrying out the reactions at milder conditions, to achieve the economically competitive production of H2. In this sense, several recent experimental works have reported promising catalytic performance for nickel supported on CeO2 (ceria)-doped with transition metals or rare earths.
In this thesis, a first-principles study of the MSR and WGS reactions over Ni/CeO2 catalysts is presented. DFT calculations, microkinetic modelling and statistical thermodynamics were employed to investigate the mechanisms governing these reactions and to examine the impact of the doping of the support and/or the alloying of nickel in the activity and selectivity of the reactions, offering an atomistic perspective of the catalyst’s behavior and properties.
Chapter 1 introduces the problematic that motivates this work. Chapter 2 describes the theory behind the computational methods employed. The subsequent chapters present the results of the study. Chapters 3 and 4 are devoted to pristine cerium oxide as an active support, analyzing its doping and reactivity. Chapter 3 presents a study of Pr-doping and its effect on the surface reactivity, whereas Chapter 4 shows an analysis of CeO2 resistance towards sulfur poisoning. On the other hand, Chapters 5 and 6 are focused on the study of the reactions of interest over Ni/CeO2 catalysts. Chapter 5 presents a study of the WGS reaction, describing the reaction mechanism on the CeO2 support and the impact of Ni-Cu alloying on its selectivity. Similarly, Chapter 6 puts the focus on the MSR reaction, presenting a complete reaction mechanism and identifying the effect of Zr-doping. Finally, Chapter 7 summarizes the main conclusions and perspectives of this thesis."
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