...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>Physical review >Surface reactivity of V_2O_5(001): Effects of vacancies, protonation, hydroxylation, and chlorination
【24h】

Surface reactivity of V_2O_5(001): Effects of vacancies, protonation, hydroxylation, and chlorination

机译：V_2O_5（001）的表面反应性：空位，质子化，羟基化和氯化的影响

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Using density-functional theory we analyze the thermodynamic stability of partially reduced, protonated, hydroxylated, and chlorinated V_2O_5(001) surfaces under flue gas conditions. These surfaces are characterized geometrically through surface relaxation calculations and electronically through charge distribution and density-of-states analysis to understand the change in surface reactivity under different pressure and temperature conditions, with a primary focus on coal-fired flue gas conditions. The stoichiometric surface is found to be the most favorable termination under flue gas conditions, but at low oxygen partial pressures (i.e., ultra-high-vacuum conditions) and elevated temperatures, the partially reduced V_2O_5(001) surfaces with one or two vanadyl oxygen vacancies are found to be stable. A surface semiconductor-to-metal transformation takes place with the addition of oxygen vacancies indicated by a decrease in the band gap. The protonation of the V_2O_5(001) surface only takes place at low oxygen partial pressures where the main source or sink of hydrogen atoms comes from H_2. The study of the thermodynamic stability of protonated surfaces and surfaces with dissociated water with both H- and OH- groups indicated that these surfaces are not stable under flue gas conditions. Chlorinated surfaces were not stable under the flue gas and the coverage conditions tested. Larger HC1 concentrations or smaller coverages may lead to stable chlorinated structures; however, the small coverages required to accurately represent the chlorine flue gas concentrations would require much larger unit-cell sizes that would be too computationally expensive. From this work it is evident that the stoichiometric surface of V_2O_5 is the most stable under flue gas conditions, and likely reactivity corresponding to NO_x reduction, surface chlorination, and mercury oxidation stems from support effects on the vanadia catalyst, which influences the vanadium oxidation state and subsequent surface reactivity.
机译：使用密度泛函理论，我们分析了在烟气条件下部分还原，质子化，羟基化和氯化的V_2O_5（001）表面的热力学稳定性。这些表面通过表面弛豫计算进行几何表征，并通过电荷分布和状态密度分析以电子方式表征，以了解在不同压力和温度条件下表面反应性的变化，主要侧重于燃煤烟气条件。在烟气条件下，化学计量表面是最有利的终止条件，但是在低氧分压（即，超高真空条件）和高温下，具有一或两个氧钒基氧的部分还原的V_2O_5（001）表面发现空缺是稳定的。表面半导体到金属的转变通过增加带隙减小表示的氧空位而发生。 V_2O_5（001）表面的质子化仅在低氧分压下发生，其中氢原子的主要来源或吸收者来自H_2。对质子化表面和带有H-和OH-基团的离解水表面的热力学稳定性的研究表明，这些表面在烟气条件下不稳定。在烟气和测试的覆盖条件下，氯化表面不稳定。较高的HCl浓度或较小的覆盖范围可能导致稳定的氯化结构；然而，准确表示氯气浓度所需的小覆盖范围将需要大得多的晶胞尺寸，这在计算上会过于昂贵。从这项工作可以看出，V_2O_5的化学计量表面在烟气条件下最稳定，并且可能对应于NO_x还原，表面氯化和汞氧化的反应性源于对钒催化剂的支持作用，从而影响钒的氧化态。以及随后的表面反应性。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号