Open Research Subjects
Postgraduate/ Undergraduate Diploma Theses
- Abatement of volatile organic compounds (VOCs) over noble metals-free mixed oxides
Volatile organic compounds (VOCs) are environmental pollutants that can originate from petroleum refineries, fossil fuels utilization, etc. VOCs include a variety of chemical compounds, some of which have short- and long-term adverse health effects. VOCs can also act as precursors for the formation of tropospheric ozone and smog.
The catalytic oxidation is among the most efficient and environmentally friendly control technologies for VOCs abatement. Noble metals (NMs)-based catalysts, like Pt and Pd, are among the most suitable materials for VOC abatement, since they are characterized by high activity at low temperatures and adequate stability. However, their high cost and limited abundance have recently stimulated the research for NMs-free catalytic systems. In this regard, the present thesis aims at exploring the VOC oxidation performance of various mixed oxides, such as CeO2-based catalysts. Particular emphasis will be devoted on the elucidation of mixed oxides surface chemistry by means of several characterization techniques (XRD, SEM, TPR, XPS, etc) towards establishing rigorous structure-activity correlations.
- Nitrous oxide (N2O) decomposition over Ceria-based mixed oxides
Nitrous oxide (N2O) is a powerful greenhouse gas, contributing also to stratospheric ozone depletion. Nowadays, N2O emissions are significantly increased compared to the pre-industrial period due to human activities including among others the combustion of fossil fuels, the use of fertilizers, the production of nitric and adipic acid, etc.
Among the different remediation methods, end-of-pipe catalytic technologies represent the most promising choices due to their lower cost. Pt-, Pd- and Rh- based catalysts exhibit satisfactory activity at low temperatures; however, their high cost represents an important obstacle toward practical applications.
In this regard, the development of catalyst composites of low cost and adequate activity is of paramount important in the field of environmental catalysis. Ceria-based oxides are amongst the most promising materials in the field of environmental catalysis due to the unique physicochemical properties of ceria in conjunction to the peculiar interfacial reactivity that can be obtained by combining the ceria with various transition metals.
The present thesis aims at exploring the deN2O performance of various CeO2-based catalysts, such as Co-Ce composites. Particular emphasis will be devoted on the elucidation of mixed oxides surface chemistry by means of several characterization techniques (XRD, SEM, TPR, XPS, etc) towards establishing rigorous structure-activity correlations.
- Surface characterization by means of X-ray photoelectron spectroscopy (XPS) of cobalt-ceria mixed oxides
Cobalt based catalysts have recently attracted considerable interest in the fields of heterogeneous catalysts and electro-catalysis as promising alternatives to noble metal based catalysts. Their enhanced electro-catalytic activity in conjunction with their adequate stability render these composites suitable for several environmental and energy applications. In this regard it is crucial to gain insight into the fundamental understanding of their unique physicochemical characteristics. X-ray photoelectron spectroscopy is one of the most powerful characterization techniques to obtain information about the elemental chemical states and surface composition.
- Carbon to Electricity in a novel Fuel Cell utilizing Greek minerals
The worldwide growing energy demand cannot only be compensated by the renewable energy sources. Moreover, hydrogen energy market is at an early stage, notably hampered by the high production, storage and distribution costs. On the other hand, coal is by far the most abundant and economic fossil fuel resource, covering more than 25% of the world’s energy consumption. Especially in Greece, lignite coal is by far the prevailing source for power generation holding more than ~70%.
However, the low energy conversion efficiency of solid lignite attained in conventional coal-fired plants along with the vast amount of greenhouse gas emissions, are major drawbacks towards the effective conversion of lignite to energy. In this regard, the utilization of lignite with an environmental friendly and highly effective manner is of paramount importance. Recently, the development of high efficiency Direct Carbon Solid Oxide Fuel Cells (DC-SOFC) is explored in the framework of European Union-FP7/RFCS research programme-link.
In the present thesis the feasibility of employing lignite as fuel in a DC-SOFC will be explored. The recent trends in the field will be firstly surveyed. The DC-SOFC performance of lignite-fed SOFC will be investigated. Several parameters related to the impact of fuel characteristics, temperature, purging gas, etc. on fuel cell performance will be explored.
- Effect on nanoceria morphology/structure on the solid state properties of ceria-based composites
The objective of present thesis is the synthesis of novel nano-structured ceria based non-noble metal catalysts which are characterized by low cost and high activity/stability. Particular emphasis will be devoted on the impact of ceria structure/morphology on the solid state properties and in consequence on the catalytic performance of ceria-based oxides, such as CuO-CeO2, Co3O4-CeO2, etc. Various synthesis methods will be used, involving the hydrothermal, the microwave and the co-precipitation synthesis.
The as prepared materials will be used in energy and environmental catalytic processes such as the hydrogenation of carbon dioxide (CO2) toward value added products (e.g. methane, methanol) and the control of environmental pollutants (NOx, N2O, VOCs). Various characterization studies will be employed to gain insight into the impact of preparation method on the physicochemical and catalytic properties of the obtained materials.