278626 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 . 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 . In fact, it has been shown that solar energy is capable to initiate the dissociation of H2O and CO2 on a CeO2 catalyst . Moreover, CeO2 is a highly interesting material for CO2storage and subsequent reduction due to its superior redox capacity .
Here, density functional theory within the Gaussian and plane waves formalism implemented in the QUICKSTEP  module of the CP2K  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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