Adsorption of CO2 on a PdO(101) Thin Film

作者：Hinojosa Jose A Jr; Antony Abbin; Hakanoglu Can; Asthagiri Aravind; Weaver Jason F^*

来源：Journal of Physical Chemistry C, 2012, 116(4): 3007-3016.

DOI：10.1021/jp2104243

We investigated the adsorption of CO2 on PdO(101) using temperature-programmed desorption (TPD) and dispersion-corrected density functional theory calculations (DFT-D3). We find that CO2 desorbs from PdO(101) in two main TPD peaks (epsilon(1) and epsilon(2)) centered at similar to 176 and 120 K and estimate that the average binding energies in the epsilon(1) and epsilon(2) states are 54 +/- 8 and 37 +/- 5 kJ/mob respectively. The CO2 layer saturates on PdO(101) at a total coverage of similar to 0.47 monolayer (ML), with the CO2 molecules distributed nearly evenly between the two adsorbed states. TPD experiments of CO2 adsorption onto preadsorbed layers of pure O-18(2) and H2O provide evidence that the epsilon(1) and epsilon(2) states correspond to CO2 molecules adsorbed on the coordinatively unsaturated (cus) vs saturated (40 Pd sites of the PdO(101) surface, respectively. DFT-D3 calculations predict CO2 saturation coverages and binding energies on PdO(101) that agree well with our experimental estimates. The calculations suggest that CO2 prefers to adsorb initially on a cus-Pd site in an upright, linear configuration and that CO2 dialers and trimers form on the cus-Pd row as the CO2 coverage increases. The dimers and trimers consist of CO2 molecules adsorbed in alternating bent and linear geometries. The calculations predict that CO2 trimers saturate the cus-Pd row at a coverage of 0.26 ML and that further increases in coverage cause CO2 to physisorb on the 4f-Pd sites until the CO2 layer saturates at a total coverage of 0.52 ML. DFT-D3 indicates that dispersion and electrostatic interactions govern the binding of CO2 on the cus-Pd rows of PdO(101).

• 出版日期2012-2-2