Coupling Sol-Gel with Microwave Radiation Towards Synthesis of Ce-Sm-Cu-O Catalysts for CO Oxidation Reaction

  • Ayesha A. Alkhoori

Student thesis: Master's Thesis


The high demand for clean energy based on hydrogen has increased recently in fuel cells application such as proton exchange fuel cells (PEMFCs), due to its enhanced efficiency and environmentally friendly attributes in generating electricity with zero emissions. Nonetheless, its performance is commonly limited by the occurrence of CO impurities (of about 2 vol.%) in the supply stream, which cause poisoning of the noble metal (i.e. Pt) electrode. To reach an optimal hydrogen fuel cell performance, pre-conditioning of the supply stream with an appropriate CO cleanup process is essential. Ceria-based mixed-metal oxides have attracted a great deal of attention in catalysis due to the fascinating redox properties. This study, investigates the doping effect on ternary ceria-based materials prepared through a time and cost-effective microwave (MW) synthesis. The microwave (MW) prepared cerium-samarium-copper mixed-metal oxide (Ce-Sm-xCu-O, where x varies between 0–20 at.%) catalysts are a great option for CO-clean up processes. Three different sets of samples were prepared and examined, the first studies the effect of different at.% copper loading, the second set characterizes the effect of various solvents i.e. water, ethanol and 1-propanol and the last set investigates the effect of simultaneous air cooling with the MW preparation method. Different characterization techniques were employed in order to study the microwave prepared materials such as FTIR, TGA/DSC, BET, SEM/EDX, XRD, Raman, XPS, H2-TPR, CO2-TPD and catalytic activity. The Scanning Electron Microscopy (SEM) results for different copper composition showed that the synthesized materials have a similar morphology of irregular meso/macroporous shapes. While, X-ray Diffraction (XRD) examined the structure of the materials, and showed that the samples have the same cubic structure as the ceria sample. The calculated crystallite sizes for all the catalysts were found to be in the 9.3–27 nm range. The thermal stability of Ce-Sm-Cu-O was further investigated in an inert atmosphere (N2) using Thermogravimetric Analysis (TGA), which allowed the decomposition process of the catalysts' precursors to be monitored. In addition, Fourier Transform Infrared (FTIR) spectroscopy was used to identify the chemical bonds and the functional groups in the catalysts before and after calcination. After that, to analyse the material's surface, porosimetry test (BET) was carried out with adsorption and desorption methodologies. The surface area of the samples ranged between 1.7–14.8 m2/g. In addition, Raman studies were used to investigate the formation of Ce-Sm solid solution and oxygen vacancies, the latter in agreement with the reducibility studies (H2-TPR). The XPS core level spectra showed the presence of Ce4+, Sm3+ and Cu2+ on the surface of the catalysts. Catalytic activity studies showed that there is a strong effect of copper at.% loading on the T50 of the reaction, where the best performance was observed for the 20 at.% Cu. Neither the change in the solvent nor the synthesis method appeared to affect the activity (i.e. T50). On the other hand, introducing CO2 in the gas feed mixture—in order to simulate more realistic conditions—caused a drop in the activity due to the competitive coadsorption of CO and CO2 species on the surface.
Date of AwardNov 2017
Original languageAmerican English
SupervisorKyriaki Polychronopoulou (Supervisor)


  • catalytic activity
  • microwave synthesis
  • mixed-metal oxides
  • copper catalysts
  • CO oxidation
  • ceria based materials.

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