在上催化水的形成:一项第一原则研究
1School of Chemistry, The Queen's University of Belfast, Belfast BT9 5AG, UK.
Journal of the American Chemical Society
|July 18, 2001
概括
金上的水形成是复杂的. 密度函数理论揭示,虽然初始的O化缓慢,但水作为自催化剂,通过不成比例反应促进后续步骤.
科学领域:
- 表面科学是一门科学.
- 催化剂是一种催化剂.
- 计算化学是一种计算化学.
背景情况:
- 在上将氧 (O) 化为水 (H2O) 是一个基本的催化过程.
- 尽管反应机制看起来很简单,但它仍然是争论的主题.
研究的目的:
- 通过计算方法研究在上氧化的基本步骤的微观反应途径.
- 阐明中间体和替代反应路径在水形成中的作用.
主要方法:
- 使用了密度函数理论 (DFT) 和梯度校正.
- 计算了关键基本步骤的微观反应路径和能量障碍.
主要成果:
- 从化学吸收的O和H原子中形成H2O是高度激活的,最初的H添加到O (形成OH) 是限制速度的步骤 (约. 一个电荷障碍).
- 随后的OH到H2O的化很容易 (大约. 0.2 eV的屏障).这是一个很大的障碍.
- 涉及H2O和O的不成比例反应为OH形成提供较低的激活障碍,表明H2O作为自催化剂.
- 2:1的H2O:O不成比例在动力学和热力学上比1:1的固体几何学更受青.
结论:
- 水 (H2O) 在上本身形成时起自催化剂的作用,特别是通过 2:1 不成比例.
- 混合OH和H2O覆盖层在低温下可能是关键中间体.
- 质子转移机制可能会促进最后的化步骤H2O.
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