隔离金属活性部位度和稳定性控制催化剂二氧化碳减排选择性
John C Matsubu1, Vanessa N Yang, Phillip Christopher
1Department of Chemical & Environmental Engineering, and ‡Program in Materials Science and Engineering, University of California, Riverside , Riverside, California 92521, United States.
Journal of the American Chemical Society
|February 12, 2015
概括
这项研究表明,在TiO2上分离的原子和纳米颗粒对CO2化具有明显的催化选择性. 纳米粒子分解到孤立的部位会影响随着时间的推移催化剂的稳定性和反应性.
科学领域:
- 不同质的催化剂.
- 表面科学是一门科学.
- 材料化学 材料化学
背景情况:
- 二氧化碳化对于化学合成至关重要,但其原子尺度机制尚不清楚.
- 金属颗粒大小对催化剂稳定性,活性位点分布,反应性和选择性的影响至关重要,但往往忽略了孤立的位点.
- 了解二氧化碳减排中的结构功能关系对于开发高效的催化过程至关重要.
研究的目的:
- 在TiO2催化剂上量化分离 (Rhiso) 与纳米粒子支持 (RhNP) 位点的比例.
- 在二氧化碳化反应中,将 Rhiso 和 RhNP 位点的丰度与催化活性和选择性相关联.
- 调查纳米颗粒稳定性和转化到隔离地点对随时间推移的催化剂性能的作用.
主要方法:
- 使用散射反射红外里叶变换光谱 (DRIFTS) 与探针分子来区分和量化 Rhiso 和 RhNP 位点.
- 采用特定地点的灭绝系数来准确量化地点.
- 进行了催化反应 (反向水气转移和甲化),以评估活性和选择性.
主要成果:
- 在逆水气转移的周转频率 (TOF) 和Rhiso站点的比例之间建立了强烈的相关性.
- 观察到甲化TOF和RhNP位点的部分之间的相关性.
- 证明在反应条件下纳米颗粒分解到Rhiso位点,会随着时间的推移影响催化剂活性和稳定性的变化.
结论:
- 同一个金属 (Rh) 的孤立原子和纳米粒子在同一个支物 (TiO2) 上,在二氧化碳化过程中对竞争反应途径具有明显的催化选择性.
- Rh纳米颗粒的动态转化到孤立的部位显著影响催化剂的稳定性和性能.
- 这项工作强调了将孤立的原子和纳米粒子视为异质催化中的活性位点的重要性.
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