We studied the mechanism of CO oxidation catalyzed by CeO2(111) and CeO2(100) supported sub-nanometer-sized Pt9 nanoparticles (NPs) by density functional theory (DFT). By developing a fully CO-covered NP models for catalysis studies, we investigated the catalytic performance of both systems under the real CO oxidation condition where CO molecules cover a large portion of NP surface. Sequentially calculated binding energy of CO on Pt NPs supported on both CeO2 supports showed that the CO coverage of NPs cannot reach 1 ML due to spatial restriction at the NP-CeO2 perimeter. Because the NPs cannot strongly coadsorb CO and O2 molecules, we constructed the CO oxidation pathway using the most weakly bound CO molecule and lattice oxygen of CeO2 support. Interestingly, the formation of CO2 like intermediates was spontaneous at high CO coverage. Rather, the final CO2 releasing step was rate determining. Complete Mars-van Krevelen type of pathways in each system predict that NPs supported on the less-stable CeO2(100) relatively easily release the produced CO2 molecules. The results show that the stronger NP-support interaction on CeO2(100) leads to the weaker NP-CO binding. We found that, for oxide supported sub-nanometer-sized NPs, the support-NP interaction directly affects the NP-adsorbate interaction and eventually the energetics of CO2 production which is the rate determining step.

Density functional theory study of reactivity of CeO2-supported Pt nanoparticles for the CO oxidation

253rd National Meeting (2017)

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