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1、X射线吸收精细结构谱XAFS （实验方法和应用）,Web of Science Search: “EXAFS” or “XAFS” (but not “XAS” too many false hits) 1971-1975: 8 Publications Last year: 743 Publications Last 10 years: 7,199 Publications,XAFS Beamline Design Parameter,位于第三代上海同步辐射装置的BL14W1 是一个高性能的X射线吸收谱光束线站。在一期的七条光束线站中BL14W1设计为通用吸收谱线站。BL14W1 的光源是一
2、个38极Wiggler插入件，最大磁场为1.2T，磁场周期为80mm. XAFS光束线的主要光学部件包括一个准直镜，一个配有Si (111) 和 Si (311)的液氮冷却双晶单色器，一个聚焦镜，一个高次谐波抑制镜。光束线有聚焦和非聚焦两种工作模式，其中，聚焦模式下能量范围为422.5keV，非聚焦模式下的能量范围为3.550keV。,国内外同类线站性能比较,Experimental Station,Potential capability Minimum Detection Limit 1ppm,It is a general and high performance XAFS beamli
3、ne, with high flux、high signal/noise ratio and fast data collection.,XAFS analytical techniques at SSRF,32元高纯Ge探测器及XIA电子学系统 4元Si漂移探测器及采集系统 Lytle 荧光电离室 Oxford 电离室 五维样品台 掠入射平台 低温样品室 (4K) 和高温炉,XAFS线站主要仪器设备,XAFS线站主要实验技术,透射 XAFS （Transmission XAFS） 荧光 XAFS（Fluoresce XAFS） 掠入射 XAFS （Grazing Incident XAFS）
4、 原位 XAFS （In situ XAFS ） 快速 XAFS (QXAFS),Conventional XAFS and QXAFS spectra (5 Sec) of Cu foil at K edge measured at BL14W1 beamline in comparison with standard XAFS spectra (the data is from Chicago University XAFS library, which was measured in APS 13ID),comparison with APS standard XAFS spectra,
5、SR-XAFS实验框图,XAFS在钙钛矿催化剂研究中的应用,汽车尾气污染问题严重,汽车尾气的污染物，CO、HC以及NOx等，严重威胁到人类的生活，对其治理受到全球范围的重视。 世界上污染最为严重的二十个城市，出现频率最高的就是中国的城市，占据60%。 大气污染问题与汽车尾气排放具有很高的相关性。 引起的呼吸系统疾病(主要是慢性阻塞性肺病)在我国城市居民主要疾病死亡构成中占12.6%，59%以上的司机患有不同程度的呼吸道疾病 国内不断提高汽车尾气排放处理标准。 国内在尾气处理催化剂研究人员众多。,Mazda: Worlds first application of single-nanocata
6、lyst technology in catalytic converters,Self-regeneration of a Pd-perovskite catalyst for automotive emissions control,用XAFS手段研究催化材料的重生问题，研究其反应前后的结构变化，发现其在催化反应前后所处晶格和配位环境差异，解释了其能长期保持高活性的原因。 SPring-8 Nature 418, 164 - 167 (11 July 2002),Improving catalytic converters,为了提高催化剂的催化效率，科学家利用同步辐射装置开展很多原位实时监
7、测反应过程的研究。XAFS可以提供很重要的在金属催化剂反应过程中，与局域结构和电子环境有关的原位动力学信息，他的动力学行为可以在ms, us,以至于ps. fs内研究。,M. A. Newton et al., Nature Materials 2007, 6, 528-532; Angew. Chem Int. Ed. 2007, 45, 8629-8631,Fig. 99: Normalised Pd K edge energy dispersive EXAFS spectra derived during a switch from a 5%NO/He feed to a 5%CO/He
8、 feed (both 75mlmin1 flow) at 673 K over a 1wt%Pd/10ZCA sample. Each spectrum was acquired in ca. 250 msecs. For clarity only 1 spectrum/second is plotted. The red to yellow shading is indicative of the switch from the NO to CO feed.,Fig. 100: Infrared spectra (averaged over 9 reversible NO/CO switc
9、hes) taken at the same time as the EXAFS spectra shown in Figure 99, collected with a 3 Hz spectral acquistion speed. The major gas phase and surface functionalities observed during the experiment are indicated. Again the shading of the flow of the graph indicates the change of reactive feedstock.,国
10、内的研究,汽车尾气净化装置及催化剂,通过EXAFS研究助剂Fe的添加对催化剂Pt/Ba/Al2O3 中Pt物种微观结构的影响，这种微观结构的改变对催化剂组分间的作用和催化性能产生了显著影响。 Meng M et al.Applied Catalysis B: Environmental 78 (2008) 38,XAFS在电化学研究中应用,“Ethanol is one of the most ideal reactants for fuel cells,” said Brookhaven chemist Radoslav Adzic. “Its easy to produce, renewa
11、ble, nontoxic, relatively easy to transport, and it has a high energy density. A major hurdle to the commercial use of direct ethanol fuel cells is the molecules slow, inefficient oxidation, which breaks the compound into hydrogen ions and electrons that are needed to generate electricity. Specifica
12、lly, scientists have been unable to find a catalyst capable of breaking the bonds between ethanols carbon atoms. But at Brookhaven, scientists have found a winner. Made of platinum and rhodium atoms on carbon-supported tin dioxide nanoparticles, the research teams electrocatalyst is capable of break
13、ing carbon bonds at room temperature and efficiently oxidizing ethanol into carbon dioxide as the main reaction product. Other catalysts, by comparison, produce acetalhyde and acetic acid as the main products, which make them unsuitable for power generation.,氢电池：储存、运输困难 甲醇电池：CO中间物质 乙醇电池：氧化困难，,“The a
14、bility to split the carbon-carbon bond and generate CO2 at room temperature is a completely new feature of catalysis,” Adzic said. “There are no other catalysts that can achieve this at practical potentials.”,The main absorption peaks at the Rh and Pt edges have a very small potential dependence, in
15、dicating that the surfaces are only slightly oxidized, unlike the process that occurs with the pure Rh phase. It is likely that OH, which is present on the SnO2 surface in aqueous solutions, causes a shift in surface oxidation of Rh and Pt (Rh or PtOH formation),Measurements of metal metal (RhPt and
16、 PtRh) coordination numbers NRh-Pt and NPt-Rh enabled us to obtain the average composition of the nanoparticles: x(Pt)/x(Rh) = NRh-Pt/NPt-Rh = 2.1(0.3), in reasonably good agreement with the ICP data x(Pt)/x(Rh)=1.5(0.2). The absolute values of these coordination numbers indicate the same size range (13 nm) as obtained by TEM. The obtained Pt and Rh coordination numbers have similar values 9.5(0.8) and 10.8(0.8) respectively, consistent with homogeneous distribution of Pt and Rh throughout the p
