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Combining in Situ NEXAFS Spectroscopy and CO2 Methanation Kinetics To Study Pt and Co Nanoparticle Catalysts Reveals Key Insights into the Role of Platinum in Promoted Cobalt Catalysis

Beaumont, Simon K., Alayoglu, Selim, Specht, Colin, Michalak, William D., Pushkarev, Vladimir V., Guo, Jinghua, Kruse, Norbert, Somorjai, Gabor A.
Journal of the American Chemical Society 2014 v.136 no.28 pp. 9898-9901
X-ray absorption spectroscopy, carbon dioxide, catalysts, catalytic activity, cobalt, hydrogen, hydrogenation, nanoparticles, platinum, synthetic fuels, temperature
The mechanistic role of platinum and precious metals in promoting cobalt hydrogenation catalysts of the type used in reactions such as Fischer–Tropsch synthesis is highly debated. Here we use well-defined monometallic Pt and Co nanoparticles (NPs) and CO₂ methanation as a probe reaction to show that Pt NPs deposited near Co NPs can enhance the CO₂ methanation rate by up to a factor of 6 per Co surface atom. In situ NEXAFS spectroscopy of these same Pt NP plus Co NP systems in hydrogen shows that the presence of nearby Pt NPs is able to significantly enhance reduction of the Co at temperatures relevant to Fischer–Tropsch synthesis and CO₂ methanation. The mechanistic role of Pt in these reactions is discussed in light of these findings.