(73e) Investigation of the CO2 Reaction Mechanisms On CeO2(111) and Ni/CeO2(111) Using Density Functional Theory

High energy consumption is one of the major problems of our society created by high-velocity means of transportation, such as airplanes, by heating systems or the simple use of electric light. Most of this energy is provided by combustion of fossil fuels [1]. It is assumed that, due to the rising demand of energy, natural resources of oil will be consumed within the next 80 years. These data call for alternative energy production methods based on renewable sources such as wind or solar energy. Another promising possibility, however, is the production of hydrocarbons from CO₂ and hydrogen produced from solar energy [2]. In fact, it has been shown that solar energy is capable to initiate the dissociation of H₂O and CO₂ on a CeO₂ catalyst [3]. Moreover, CeO₂ is a highly interesting material for CO₂storage and subsequent reduction due to its superior redox capacity [4].

Here, density functional theory within the Gaussian and plane waves formalism implemented in the QUICKSTEP [5] module of the CP2K [6] program package was used for the simulation of CeO₂(111) surfaces and their CO₂ storage capacity and further use of production of hydrocarbons. Therefore, the adsorption mechanisms of CO₂ on CeO₂(111) were investigated focusing on the influence of the CO₂ coverage. It could be shown that up to a CO₂ coverage of 1/3 monolayer (ML), stable monodentate carbonate species are formed with the terminated surface O atoms. Further CO₂ molecules are then adsorbed as linear species. This demonstrated that, up to 1/3 ML, stable binding and activation of CO₂ is possible and confirms CeO₂ to be suitable for CO₂ storage and activation, however, limited to a certain CO₂ coverage. The reaction mechanisms of CO₂ with H₂ have been analyzed with the most stable configuration of CO₂ at 1/3 ML coverage. Additionally, Ni-clusters deposited on the CeO₂ surface and their effect on the CO₂ reaction mechanism have been investigated and compared to experimental results. The results of this study give fundamental insight on the reaction mechanisms of CO₂ on CeO₂(111) providing information for the design of improved catalysts for production of hydrocarbons from CO₂.

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