[Zurück]

G. Pacholik, L. Enzlberger, A. Benzer, R. Rameshan, M. Latschka, Ch. Rameshan, K. Föttinger:
"In situ XPS studies of MoS2-based CO2 hydrogenation catalysts";
Journal of Physics D: Applied Physics, 54 (2021), 324002.

Various formulations of Co, Ni and K modified MoS2-based catalysts were synthesized hydrothermally and compared in their catalytic performance in CO₂ hydrogenation at 21 bar and 220 °C-330 °C. The products were CO, CH₄ and methanol. The addition of K reduced the selectivity to CH₄ and moved the maximum of the methanol formation rate to a higher temperature. The materials were characterized by N₂ physisorption, temperature programmed oxidation, temperature programmed reduction, and x-ray diffraction spectra (XRD). Under reducing conditions the catalysts were stable until 700 °C and under oxidizing conditions until 300 °C. XRD had shown mainly a MoS2 phase, as well as metal sulfide in the cobalt and nickel promoted catalysts. Different species of Mo and O were observed under reaction conditions by in situ x-ray photoelectron spectroscopy (XPS). When switching from H₂ to CO₂ + H₂ an increase in the amount of oxygen, both lattice oxygen and surface adsorbates, was observed as a consequence of CO₂ addition and H₂O formation in the reaction. The amount of lattice oxygen correlates with the minor amount of Mo(VI) detected. Increasing reaction temperature and thus conversion led to an increase of the O 1s signals at 533 eV assigned to surface OH, formate and adsorbed H₂O. XPS measurements in CO₂ + H₂ feed showed an effect of K addition on the adsorbate-related O 1s peak, which appeared at lower binding energy (532 eV) and was assigned to carbonates. This may indicate a different reaction mechanism in the presence of the promoter.

molybdenum sulfide, CO2 hydrogenation, promoter, methanol, CO, NAP-XPS

http://dx.doi.org/10.1088/1361-6463/ac006f

https://publik.tuwien.ac.at/files/publik_300063.pdf