Research and Thesis Projects

Bachelor thesis / Master thesis / Semester project

Chemical looping (CL) is a concept, which involves the spatial or temporal separation of a desired reaction into sub-reactions with the help of a chemical intermediate. Generally, these chemical intermediates are metal oxides, so-called oxygen carriers (OCs), that are reduced by donating lattice oxygen to a sub-reaction, and that are subsequently re-oxidized during a regeneration step, thus forming a closed loop regarding the overall process. An upcoming, promising field of application for the concept of CL is the production of value-added chemicals, due several of CL’s advantages such as the potential of heat integration, in-situ product separation, and in-situ conversion of by-products to circumvent limitations given by thermodynamic equilibrium¹.


The main challenge in designing competitive CL processes to produce value-added chemicals is the tendency of the OC to over-oxidize the carbon-based feedstock to CO_x, which has been linked to the mobility/diffusivity of oxygen in the metal oxide in several studies^2,3. Hence, this project aims at improving our understanding of the oxygen release and mobility of doped perovskite (ABO₃: A,B = metal cations) metal oxides as OCs and its implications on their selectivity as redox catalysts in chemical looping partial oxidation applications.


As an indicator for the oxygen mobility, the reducibility of the doped perovskites will be assessed by temperature-programmed reduction (TPR). In addition, electrical conductivity relaxation measurements will be carried out to explicitly determine the effect of doping on the oxygen diffusivity within the metal oxide structure. The tendency of the perovskites towards overoxidation of carbonaceous feedstock to CO₂ will be evaluated by catalytic experiments in a fixed-bed reactor. To quantify and understand the structural changes caused by doping, the perovskites will be analyzed by powder X-ray diffraction (XRD). Our goal is to correlate the structural changes imposed by doping to the oxygen mobility and ultimately to the catalytic performance of perovskites for partial oxidation reactions.

Contact:
Alexander Oing
LEE P224


References:
[1] Zhu, X., et al. Energy Environ. Sci. vol. 13 772–804 (2020).
[2] Zhu, X., et al. ACS Catal 8, 8213–8236 (2018).
[3] Zheng, Y. et al., Appl. Catal. B 202, 51–63 (2017).  

Bachelor thesis / Master thesis / Semester project

Anthropogenic CO₂ emissions and the resulting effects of climate change remain as some of the most pressing issues today. Consequently, various carbon capture and storage (CCS) technologies have been proposed to drastically reduce the emission of CO₂. The storage of CO₂, however, still poses a crucial challenge. Furthermore, most bulk products in chemical industry are derived from fossil sources, which results in a considerable carbon footprint of a vast number of everyday consumables. In this regard, carbon capture and utilization (CCU) technologies offer a promising solution to resolve challenges concerning the permanent storage of CO₂, by converting the greenhouse gas into value-added chemicals, which in turn, will also significantly contribute to the carbon neutrality of important chemical products [1].

Among CCU technologies, the hydrogenation of CO₂ to methanol has attracted increasing academic interest, due to the versatile applications of methanol, such as its utilization as a fuel additive or its facile conversion to further value-added bulk chemicals [2].

CO₂ + 3H₂ → CH₃OH + H₂O, ∆_HR,298K = -49.5 kJ/mol

The main challenge of this reaction is the activation of CO₂, which requires high energies and therefore high temperatures (e.g. T > 250 °C at 20 bar), at which the competing reverse water-gas shift (RWGS) reaction becomes thermodynamically favored, converting CO₂ into the undesired by-product CO [3]:

CO₂ + H₂ → CO + H₂O, ∆_HR,298K = +41.1 kJ/mol

Recently, mixed metal oxide catalysts such as ZnZrO_x have been reported to catalyze the hydrogenation of CO₂ at very high methanol selectivity (> 90 %) and good CO₂ conversion (10 %), while showing no sign of deactivation for over 500 hours of time on stream [4].

Our group is interested in attaining a fundamental understanding of catalyzing the hydrogenation of CO₂ to methanol over ZnZrO_x catalysts to fill the gaps where current knowledge is still lacking. We are also looking into finding new mixed metal oxide formulations to further increase the methanol productivity of this type of catalyst. In doing so, we synthesize the catalysts via impregnation or co-precipitation routes and subsequently carry out an in-depth structural characterization. Ultimately, the mixed metal oxides are evaluated catalytically, and the results are correlated to structural findings to establish structure-performance relationships.

What will you learn?
• An introduction to CO₂ conversion technologies
• Strategies on how to synthesize and characterize mixed metal oxide catalysts
• Working at the interface of engineering, materials science, and chemistry
• Improve your engineering skill-set and gain practical insight into state-of-the-art chemical/process engineering

Has this sparked your interest? Please feel free to apply or contact us for more information. The scope of the project can be adjusted to the necessary requirements.

Contact:
Alexander Oing
LEE P224


References:
[1] Ye, RP., et al. Nat. Commun. 10, 5698 (2019)
[2] Sternberg, A. & Bardow, A. Energy Environ. Sci. 8, 389–400 (2015)
[3] Kanuri, S. et al. Int. J. Energ. Res. 46, 5503–5522 (2022)
[4] Wang, J. et al. Sci. Adv. 3, e1701290 (2017)

Our laboratory is interested in fundamental studies of electrocatalysts for a range of applications concerning renewable energy conversion and storage, for instance biomass reforming, oxygen reduction, hydrogen and oxygen evolution, towards applications in the fuel cells, electrolyzers, etc. Therefore, we are looking for talented and motivated students who are interested in learning and mastering (1) the synthesis of oxides, carbides, nitrides as bulk solids and nanoparticles; (2) state-of-the-art ex situ and in situ physical characterization techniques; (3) electrochemical characterization of materials.

Currently, the following projects are researched in the group:

(1) Iridium and ruthenium pyrochlore oxides and oxyfluorides investigated to understand the fundamental design principles of oxygen electrocatalysis.

(2) Well-defined noble metal alloys and oxide nanoparticles as electrocatalysts for the application in fuel cells.

(3) Unlocking the potential of two-dimensional carbides and nitrides in electrocatalysis.

(4) Photoelectrocatalytic biomass reforming.

Contact:
Denis Kuznetsov

(Please, for PhD applications use the dedicated link)

Bachelor thesis / Master thesis / Semester project

Carbon capture and storage (CCS) technologies are a short- to mid-term solution to mitigate anthropogenic carbon dioxide (CO2) emissions. Solid calcium- or magnesium-based CO2 sorbents that are cycled between a carbonate and an oxide state (CaO + CO2 ↔ CaCO3 / MgO + CO2↔ MgCO3) are a promising class of carbon capture materials because they are cost-efficient and readily available. However, these materials suffer from rapid deactivation and significant performance losses during cycling. Various ways of improving these sorbents have been proposed, but a fundamental understanding of how these materials can be promoted and stabilized is still lacking.

Our lab is investigating novel Ca- and Mg-based CO2 sorbents that are modified through (i) additives that promote the CO2 uptake (ii) stabilizers that prevent the deactivation or (iii) micro- and nano-structuring. Our research is aimed at understanding the fundamental effect these changes have on the material, on both a macro- and nanoscale. In this respect, we are continuously looking for students to support our cutting-edge research on CO2 capture and to battle the inherent risks of climate change. Whether it’s a thesis, semester project or student research assistant position you are looking for, we are open for your application. Does this sound like a task for you? Then get in touch

Contact:
Maximilian Krödel

(Please, for PhD applications use the dedicated link)

What’s in for you?
• Understand sustainability and innovative technologies for CO2 capture
• Engage with the interface of engineering and materials science
• Gain insights into cutting-edge research at ETH Zürich
• Improve your engineering skill-set and gain excellent practical insights into state-of-the-art process engineering