Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
Phys Chem Chem Phys. 2010 Jun 28;12(24):6367-74. doi: 10.1039/c001683g. Epub 2010 Apr 28.
Base metal oxides have long been of interest as catalysts for oxidation of small molecules such as CO or NO, but practical applications are limited by surface poisoning processes. With growing interest in the oxidation activity of metal oxides, it is important to understand and ultimately to learn to bypass surface poisoning. RuO(2), as a model metal oxide oxidation catalyst, is active for CO oxidation under UHV conditions but is deactivated by some surface poisoning processes at ambient pressures. In this work, we use plane-wave, supercell DFT calculations to characterize the structures of carbonate and bicarbonate on the RuO(2)(110) surface and determine their thermodynamic stability by constructing phase diagrams. We find that while a surface carbonate (CO) is stable at low O(2) pressures and high CO(2) pressures, it is not stable under practical catalytic conditions. A surface bicarbonate (HCO) is more stable and deactivates the RuO(2) surface over a wide range of CO(2) and oxygen pressures in the presence of trace amounts of water. Therefore, bicarbonate is likely the species responsible for experimentally observed surface poisons that deactivates RuO(2) during CO oxidation. OH* might also be a candidate responsible for surface poisoning when CO(2) pressure is very low. This study demonstrates that surface poisoning is sensitive to reaction environments such as water and CO(2) pressures.
金属氧化物作为小分子（如 CO 或 NO）氧化的催化剂一直受到关注，但实际应用受到表面中毒过程的限制。随着对金属氧化物氧化活性的兴趣日益增加，了解并最终学会绕过表面中毒变得至关重要。RuO(2)作为一种模型金属氧化物氧化催化剂，在 UHV 条件下对 CO 氧化具有活性，但在环境压力下会被一些表面中毒过程失活。在这项工作中，我们使用平面波、超胞 DFT 计算来描述 RuO(2)(110)表面上碳酸盐和碳酸氢盐的结构，并通过构建相图来确定它们的热力学稳定性。我们发现，虽然表面碳酸盐（CO）在低 O(2)压力和高 CO(2)压力下稳定，但在实际催化条件下并不稳定。在痕量水存在下，表面碳酸氢盐（HCO）在 CO(2)和氧气压力的广泛范围内更稳定，并且会使 RuO(2)表面失活。因此，碳酸氢盐可能是导致实验观察到的 RuO(2)在 CO 氧化过程中失活的表面毒物的物质。当 CO(2)压力非常低时，OH*也可能是导致表面中毒的候选物质。本研究表明，表面中毒对反应环境（如水和 CO(2)压力）敏感。
