讲座题目：Thermal Switch of Nanoparticle Reactivity in Metal-Catalyzed Ammonia Borane Hydrolysis（物理学系列学术报告） .

主讲人：Chongzheng Na教授 .

主持人：潘丽坤 .

开始时间：2016-01-18 10:00 .

讲座地址：中北校区理科大楼A510 .

.

报告人简介：

 Prof. Chongzheng Na obtained bachelor’s, master’s, and Ph.D. degrees  from Tsinghua University (China), Pennsylvania State University, and the  University of Michigan, all in Environmental Engineering. He was  further trained in Environmental Chemistry as a postdoctoral fellow at  Harvard University. Before joining Texas Tech University, he was an  assistant professor at the University of Notre Dame in Indiana. At Texas  Tech University, his teaching and research focus on developing  innovative solutions of environmental challenges using nanomaterials. Up  to now, he has published over 50 peer-reviewed articles including  Langmuir, Nature Communications, PNAS, Environmental Science &  Technology, Water Research, and 2 USA patents as well as 1 book.

报告摘要：

Metal-catalyzed hydrolysis is an important reaction for releasing  hydrogen stored in ammonia borane, a promising fuel form for the future  hydrogen economy, under ambient conditions. A variety of catalysts made  of different transition metals have been investigated to improve the  efficiency of hydrogen generation using nanoparticles, following the  conventional “smaller-is-better” rationale. Using ruthenium  nanoparticles having diameters between 2 to 3.8 nm as model catalysts, I  will show that although the inverse activity-size correlation is  observed under 17.4oC, the correlation is reversed above 17.4oC,  creating a “bigger-is-better” scenario. These observations suggest the  existence of a thermal switch, formally referred to as the isokinetic  temperature, at 17.4oC for metal-catalyzed ammonia borane. As the  reaction temperature increases from below the isokinetic temperature,  the kinetics of the hydrolysis reaction transitions from an  enthalpy-controlled regime to an entropy-controlled regime. These  results highlight the importance of understanding the thermodynamic  driving forces of heterogeneous catalysis involving nanoparticles for  environmental and energy applications.