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 .
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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.
