在基于Ternary LaSi的电极上合成氨:通过第三种金属调整催化机制
Hongchen Li1, Yutong Gong1, Hongliang Yang1
1State Key Laboratory of Solidification Processing, School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaanxi, 710072, P. R. China.
ChemSusChem
|August 16, 2023
概括
金属间电极对氨合成具有惊人的催化活性. 在LaCoSi中较低的阳离子电子密度意外导致了最高的催化性能,揭示了对电极催化剂机制的新见解.
科学领域:
- 材料科学 材料科学 材料科学
- 催化剂是一种催化剂.
- 表面化学 表面化学
背景情况:
- 金属间电极因其独特的电子结构和强大的催化能力在温和条件下激活具有挑战性的化学键而闻名.
- 电极中的阳离子电子的丰富度与它们的催化效率之间的准确相关性仍然不太清楚,这阻碍了确定关键性能决定因素.
- 了解这些因素对于推进电极催化剂在各种化学过程中的设计和应用至关重要.
研究的目的:
- 研究一系列金属间电极类催化剂,特别是La-TM-Si (TM=Co,Fe,Mn) 中阴离子电子密度和催化性能之间的关系.
- 阐明控制这些催化剂的氨合成的基本机制,并确定控制它们活动的因素.
- 探索从已确立的催化原理,如萨巴蒂尔缩放关系的潜在偏差.
主要方法:
- 合成和描述具有相同晶体结构但含有不同阴离子电子的金属间电极催化剂La-TM-Si (TM=Co,Fe,Mn).
- 在温和条件下对氨合成的催化性能进行实验评估.
- 第一原理计算探测反应机制,识别活性位点,并了解电极离子在N2解离和NHx形成中的作用.
主要成果:
- 尽管离子电子密度最低,但LaCoSi对氨合成具有最高的催化活性,挑战了最初的预期.
- 第一原理计算显示,电极离子促进N2解离,改变氨合成的速度决定步骤 (RDS).
- 确定了LaCoSi和LaFeSi的双位点机制,涉及N2解离 (过渡金属) 和NHx形成 (La) 的单独位点,这打破了萨巴蒂尔缩放关系. 虽然LaMnSi对N2激活有效,但其活动受到缩放关系的限制.
结论:
- 金属间电极的催化性能不仅仅取决于阳离子电子的丰富性;不同元素和活性位点之间的相互作用是至关重要的.
- 在LaCoSi和LaFeSi中发现的双位点机制为设计规避传统缩放限制的高性能催化剂提供了一个新的范式.
- 这些发现为金属间电极催化剂的工作机制提供了重要的新见解,为合理的催化剂设计铺平了道路.
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