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>Ultrafast time-resolved quantum cascade laser diagnostic for revealing the role of surface formate species in the photocatalytic oxidation of methanol
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Ultrafast time-resolved quantum cascade laser diagnostic for revealing the role of surface formate species in the photocatalytic oxidation of methanol
In the present work, a new quantum cascade laser (QCL)-assistedoperandoFT-IR setup was used to obtain direct insight into the relationship between the overall catalytic performance of TiO(2)photocatalysts in the gas phase photooxidation of methanol at 25 degrees C, and the kinetics of intermediate surface formate species. Apparent rates of formation (R-app,R-f) and reaction (R-app,R-r) of surface formates over three different TiO(2)photocatalysts (P25, commercial anatase, and homemade anatase) have been determined through UV on-off cycles under flowing methanol and oxygen. We show that theR(app,r)follows the same trend as the overall catalytic activity in terms of total yield of methylformate and carbon dioxide, namely the following: TiO(2)P25 approximate to commercial anatase > homemade anatase. So, the faster the reaction of the surface formates, the higher the catalytic methanol oxidation activity. Thereby, we demonstrate, to our knowledge for the first time, the direct relationship between the conversion of surface formate species and the catalytic performance of the photocatalysts. Through photocatalytic tests without oxygen in the reaction feed, we also show that the crystallinity of TiO(2)impacts the availability of its lattice oxygen to contribute for both the formation and conversion of formate species. Indeed, the absence of flowing oxygen reduces theR(app,f)over TiO(2)CA by a factor 2 while it does not affect that over TiO(2)P25, and it reduces theR(app,r)over TiO(2)CA about 4 times more than that over TiO(2)P25.
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机译：在目前的工作,一个新的量子级联激光器(QCL) -assistedoperandoFT-IR被用来设置获得直接洞察的关系整体的催化性能之间的关系TiO(2)催化剂在气相光致氧化甲醇在25摄氏度,甲酸中间表面的动力学物种。和反应(R-app rr)表面整合三种不同TiO(2)论文(P25、商业锐钛矿和自制的锐钛矿)通过紫外线下开关周期确定流动甲醇和氧气。其他(app, r)总体遵循相同的趋势催化活性的总收率methylformate和二氧化碳,即: TiO (2) P25近似商业锐钛矿>自制的锐钛矿。表面反应的整合,越高催化甲醇氧化的活动。我们证明,据我们所知第一时间,之间的直接关系转换的表面和甲酸物种催化剂的催化性能。通过光催化测试没有氧气反应,我们也显示结晶度的TiO(2)影响可用性的晶格氧的贡献甲酸的物种形成和转换。事实上,缺乏流动氧气减少其他(应用f) TiO (2) CA时2倍不影响,在TiO (2) P25,和它吗减少其他(app, r)在TiO (2) CA的4倍,以上TiO (2) P25。
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