Promotion of CO oxidation on PdO(101) by adsorbed H2O

SURFACE SCIENCE

卷:650

Article

Choi, Juhee¹  Pan, Li²  Mehar, Vikram¹  Zhang, Feng¹  Asthagiri, Aravind²  Weaver, Jason F.¹ 

[1] Univ Florida, Dept Chem Engn, Gainesville, FL 32611 USA

[2] Ohio State Univ, William G Lowrie Chem & Biomol Engn, Columbus, OH 43210 USA

关键词: CO oxidation;    PdO;    Pd;    Water adsorption;    DFT;    RAIRS;   

DOI  :  10.1016/j.susc.2015.08.043

来源: Elsevier

【 摘 要 】

We investigated the influence of adsorbed H2O on the oxidation of CO on PdO(101) using temperature programmed reaction spectroscopy (TPRS), reflection absorption infrared spectroscopy (RAIRS) and density functional theory (DFT) calculations. We find that water inhibits CO adsorption on PdO(101) by site blocking, but also provides a more facile pathway for CO oxidation compared with the bare oxide surface. In the presence of adsorbed H2O, the oxidation of CO on PdO(101) produces a CO2 TPRS peak that is centered at a temperature similar to 50 K lower than the main CO2 TPRS peak arising from CO oxidation on clean PdO(101) (similar to 330 vs. 380 K). RAIRS shows that CO continues to adsorb on atop-Pd sites of PdO(101) when H2O is co-adsorbed, and provides no evidence of other reactive intermediates. DFT calculations predict that the CO oxidation mechanism follows the same steps for CO adsorbed on PdO(101) with and without co-adsorbed H2O, wherein an atop-CO species recombines with an oxygen atom from the oxide surface lattice. According to DFT, hydrogen bonding interactions with adsorbed H2O species stabilize the carboxyl-like transition structure and intermediate that result from the initial recombination of CO and O on the PdO(101) surface. This stabilization lowers the energy barrier for CO oxidation on PdO(101) by similar to 10 kJ/mol, in good agreement with our experimental estimate. (C) 2015 Elsevier B.V. All rights reserved.

【 授权许可】

Free