Surface Photocatalysis at a Single Molecule Level
Abstract:
Heterogeneous photocatalysis is an important area of research and has received great attentions from chemists, physicists as well as material scientists because of its potential applications in energy and environmental science and technology. For many years, surface photocatalysis was predominantly viewed as an electron or hole driven event. However, the detailed physical picture of how a specific surface photocatalytic reaction takes place remains unclear. During the last ten years or so, we have developed a series of new experimental tools (2PPE, TOF-TPD and STM) in our laboratory for the purpose to investigate photocatalysis of methanol, water and other molecules on TiO2 under well defined experimental conditions, and try to understand the elementary chemical reaction processes of photocatalysis of methanol and water on TiO2. Using these techniques in combination with laser-surface photocatalysis, we have observed elementary chemical reaction processes of photocatalysis of methanol and water on TiO2(110). We have shown clearly the methanol photocatalysis on TiO2(110) proceeds in a number elementary steps, that can be understood using a ground state reaction picture. Photocatalytic reaction intermediate of methanol photocatalysis on TiO2(110) has also been observed using high resolution STM at a single molecule level. In addition, strong photon energy effect on photocatalysis of both methanol and water has been observed. Experimental results also show that photocatalytic dissociation of water behaves very differently from methanol photocatalysis. A few new examples of surface photocatalysis will be also be provided. These results cannot be explained by the widely accepted photocatalysis model based on electron or hole driven chemistry model, suggesting that dynamics on surface is an important issue in photocatalysis. A dynamics based model for photocatalysis is also proposed to explain these new experimental observations.
References:
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Short bio
Prof. Xueming Yang
Distinguished Fellow, Dalian Institute of Chemical Physics, CAS.
Chair Professor, Southern University of Science and Technology.
Xueming Yang obtained his Ph.D. in chemistry at University of California at Santa Barbara in 1991. He did postdocs at Princeton from 1991 to 1993 and at UC Berkeley from 1993 to 1995. His main research focus is in the area of physical chemistry and chemical physics, especially chemical dynamics in the gas phase and at interfaces. He has developed a new generation of molecular beam instruments for quantum reaction dynamics studies, especially on quantum reaction resonances and geometric phase effects in chemical reactions. Over the last decade or so, he has developed new experimental tools to investigate surface photocatalysis that allows us to understand photocatalytic elementary reactions at single molecule level. In recent years, he has led a successful effort to develop a new VUV free electron laser at Dalian for molecular and chemical sciences. He has published more than 670 research papers in the field of laser spectroscopy, chemical dynamics and surface photocatalysis. Prof. Yang has received numerous research awards including Humboldt Research Award, Broida Prize, Tan Kah Kee Science Award, National Natural Science Award and Future Science Prize. He is an elected member of Chinese Academy of Sciences and also a Fellow of Royal Society in England. He is the current director of Chemical Science Division at National Science Foundation of China.
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