摘要
Molecular adsorption of formate and carboxyl on stoichiometric CeO2（111） and CeO2（110） surfaces was studied using periodic density functional theory （DFT＋U） calculations. Two distinguishable adsorption modes （strong and weak） of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2（110） surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with the experimental measurements. Fi- nally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species are not affected by different U parameters （U = 0, 5, and 7）. However, the calculated ad- sorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes （〈0.2 eV）. The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is neg- atively charge while the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased.
Molecular adsorption of formate and carboxyl on stoichiometric CeO2（111） and CeO2（110） surfaces was studied using periodic density functional theory （DFT＋U） calculations. Two distinguishable adsorption modes （strong and weak） of formate are identified. The bidentate configuration is more stable than the monodentate adsorption configuration. Both formate and carboxyl bind at the more open CeO2（110） surface are stronger. The calculated vibrational frequencies of two adsorbed species are consistent with the experimental measurements. Fi- nally, the effects of U parameters on the adsorption of formate and carboxyl over both CeO2 surfaces were investigated. We found that the geometrical configurations of two adsorbed species are not affected by different U parameters （U = 0, 5, and 7）. However, the calculated ad- sorption energy of carboxyl pronouncedly increases with the U value while the adsorption energy of formate only slightly changes （〈0.2 eV）. The Bader charge analysis shows the opposite charge transfer occurs for formate and carboxyl adsorption where the adsorbed formate is neg- atively charge while the adsorbed carboxyl is positively charged. Interestingly, with the increasing U parameter, the amount of charge is also increased.
基金
supported by the Laboratory Directed Research and Development(LDRD) Project of the Pacific Northwest National Laboratory(PNNL)
The computations were performed using the Molecular Science Computing Facility in the William R.Wiley Environmental Molecular Sciences Laboratory (EMSL)
a U.S.Department of Energy national scientific user facility located at PNNL in Richland,Washington
Part of the computing time was also granted by the National Energy Research Scientific Computing Center(NERSC)
