Ammonia decomposition is often used as an archetypical reaction for predicting new catalytic materials and understanding the very reason of why some reactions are sensitive on material’s structure. Core–shell or surface-segregated bimetallic nanoparticles expose outstanding activity for many heterogeneously catalysed reactions but the reasons remain elusive owing to the difficulties in experimentally characterizing active sites. Here by performing multiscale simulations in ammonia decomposition on various nickel loadings on platinum (111), we show that the very high activity of core–shell structures requires patches of the guest metal to create and sustain dual active sites: nickel terraces catalyse N−H bond breaking and nickel edge sites drive atomic nitrogen association. The structure sensitivity on these active catalysts depends profoundly on reaction conditions due to kinetically competing relevant elementary reaction steps. We expose a remarkable difference in active sites between transient and steady-state studies and provide insights into optimal material design.

Nature Communications 6, Article number: 8619 doi:10.1038/ncomms9619
Received 17 January 2015 Accepted 12 September 2015 Published 07 October 2015

http://www.nature.com/ncomms/2015/151007/ncomms9619/full/ncomms9619.html

在新能源和环保技术领域，一直困扰着科学家们的一个关键问题是如何寻找和设计高效、廉价且环境友好的催化剂材料。近日，北京理工大学物理学院姚裕贵研究团队成员郭伟博士和美国特拉华大学教授Dionisios G. Vlachos合作，在多尺度能源材料设计领域取得了重要进展。相关成果日前发表在《自然—通讯》上。

据了解，他们通过密度泛函理论结合动力学模特卡罗的多尺度计算模拟，预测了一种新型的双金属纳米功能材料：通过对一种金属纳米颗粒表面用另外一种金属作亚单层“缺陷”的修饰，能够提高2～3个数量级的催化活性。

其研究表明，通过对铂纳米颗粒表面进行镍原子亚单层修饰，能成功实现多功能催化：覆盖在铂纳米颗粒上的亚单层镍原子能有效分解氨气，同时解离的氮原子扩散到镍台阶边缘进而脱附，释放出无毒害的氮气。而氢气很容易从表面脱附，从而实现了无碳的氢气释放。这种亚单层的“缺陷”表面不但相对于完美的无缺陷表面有两到三个数量级的性能提高，也具有更易于实验合成的优点。该发现为材料设计开辟了新的可能性，即科学家可以通过调控复合材料表面的形貌和成分，从而利用材料的不可避免的不完美性以及不同组分的协同效应来完成各种复杂的反应。（来源：中国科学报 温才妃）