Fan Qi-Yuan, Sun Juan-Juan, Wang Feng, Cheng Jun
State Key Laboratory of Physical Chemistry of Solid Surface, Collaborative Innovation Center of Chemistry for Energy Materials (iChEM), College of Chemistry and Chemical Engineering, Xiamen University, Xiamen, 361005, China.
J Phys Chem Lett. 2020 Oct 1;11(19):7954-7959. doi: 10.1021/acs.jpclett.0c02499. Epub 2020 Sep 9.
Sub-nanometer metal clusters widely existing in catalysts have a large ensemble of metastable isomers that can interconvert during catalytic reactions, exhibiting complex dynamical catalytic effects. In this work, we systematically investigate the temperature dependent structural dynamics of the Cu cluster in CO dissociation using molecular dynamics and the free energy calculation method. We find an abnormal entropic effect due to adsorption-induced liquid-to-solid phase transition of the cluster during the course of the elementary dissociation step at transition temperatures. In the dissociation product, the formation of a rigid CuO unit decreases the dynamical fluidity of the cluster and increases the melting temperature, causing a decrease in the entropy of the dissociation product. Our work demonstrates the nontrivial effects of surface adsorption on phase transition behaviors of dynamic clusters and offers a new perspective to dynamic catalysis.
广泛存在于催化剂中的亚纳米金属团簇具有大量亚稳态异构体，这些异构体在催化反应过程中可以相互转化，表现出复杂的动态催化效应。在这项工作中，我们使用分子动力学和自由能计算方法系统地研究了CO解离过程中Cu团簇的温度依赖性结构动力学。我们发现在转变温度下的基元解离步骤过程中，由于团簇吸附诱导的液-固相变，出现了异常的熵效应。在解离产物中，刚性CuO单元的形成降低了团簇的动态流动性并提高了熔化温度，导致解离产物的熵降低。我们的工作证明了表面吸附对动态团簇相变行为的重要影响，并为动态催化提供了新的视角。
