Enhanced adsorption of CO2at steps of ultrathin ZnO: the importance of Zn-O geometry and coordination.
The interaction between CO2and ultrathin ZnO supported on Au(111) has been studied using temperature programmed desorption (TPD) and density functional theory (DFT) calculations. We find that CO2binds weakly on the planar ZnO bilayer and trilayer surfaces, desorbing at T = 130 K. CO2binds more strongly at the steps formed between ZnO bilayers and trilayers, desorbing at T = 285-320 K depending upon the CO2exposure. The adsorption energies determined from DFT calculations for CO2on the ZnO planar surfaces and at the steps are ∼5.8 and 19.0 kcal mol-1, respectively, agreeing with the apparent activation energies of desorption (Ed) estimated based on the TPD peaks at the limit of low CO2exposures (7.7 and 19.5 kcal mol-1, respectively). The DFT calculations further identify that the most stable adsorption configuration of CO2at the steps of ultrathin ZnO is facilitated by the geometry and coordination of the Zn cations and O anions near the step region. Specifically, the enhanced adsorption takes place via bonding of both the C and O atoms of the CO2molecule to the tri-fold coordinated O anions at the trilayer edge and to the neighboring Zn cations on the bilayer terrace, respectively, leading to CO2bending and formation of a carbonate-like species.
National Energy Technology Laboratory (NETL), United States Department of Energy, P.O. Box 10940, Pittsburgh, Pennsylvania 15236, USA. Xingyi.Deng@NETL.DOE.GOV and AECOM, P.O. Box 618, South Park, Pennsylvania 15129, USA.
Xingyi
http://orcid.org/0000-0001-9109-1443
X
Deng
National Energy Technology Laboratory (NETL), United States Department of Energy, P.O. Box 10940, Pittsburgh, Pennsylvania 15236, USA. Xingyi.Deng@NETL.DOE.GOV.
Dan C
DC
Sorescu
National Energy Technology Laboratory (NETL), United States Department of Energy, P.O. Box 10940, Pittsburgh, Pennsylvania 15236, USA. Xingyi.Deng@NETL.DOE.GOV and AECOM, P.O. Box 618, South Park, Pennsylvania 15129, USA.
Junseok
J
Lee