Catalysis high sensitivity requirement

In relation to the field of heterogeneous catalysis, an advantage of PL is that solid samples can be easily investigated. Other assets include its high sensitivity (often samples of less than a few tens of mg only are needed), the short analysis times required, and the different types of data, as discussed in the previous sections, which can be obtained from the investigation of the spectral and temporal profiles of both the excitation and emission processes (Anpo and Che, 1999). 

NMR spectroscopy can also be used to follow rates of detritiation but at the present time more attractive alternatives are available. This is because the time required to produce the spectrum, despite the inherently high sensitivity of tritium, limits the approach to fairly slow reactions. Secondly, there is the problem of having to restrict the instrument to fairly long times on a single project when others, less time consuming, but equally important, require attention. With the possible improvements in sensitivity, the above-mentioned difficulties will be greatly reduced and the attractions of the technique for studies in the catalysis area greatly enhanced. 

Hence, catalysis related challenges for SOFC cathode are the development of cathode specifications, i.e., material and microstructure, having high catalytic activity for oxygen reduction at 600 °C, high electron and ion conductivity, and a low sensitivity for poisoning by volatile Cr species. Again, as for the anode, cost and compatibility related requirements have to be considered. 

Characterization of the Surfaces of Catalysts Measurements of the Density of Surface Faces for High Surface Area Supports. - It has always been a tenet of theories of catalysis that certain reactions will proceed at different rates on different surface planes of the same crystal. Experiments with metal single crystals have vindicated this view by showing that the rate of hydrogenolysis of ethane on a nickel surface will vary from one plane to another. In contrast the rate of methanation remains constant for the same planes.4 Because of this structure sensitivity of catalytic processes there is a requirement for methods of determining the number of each of the different planes which a catalyst and its support may expose at their surfaces. Electron microscopy studies of 5nm Pt particles supported upon graphite show them to be cubo-octahedra with surfaces bound by (111) and (100) planes.5 Similar studies of Pd and Pt prepared by evaporation reveal square pyramids of size 60-200 A bounded by incomplete (111) faces.6... 

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