Catalysis films work function

It is particularly helpful that we can take the Cu-Ni system as an example of the use of successive deposition for preparing alloy films where a miscibility gap exists, and one component can diffuse readily, because this alloy system is also historically important in discussing catalysis by metals. The rate of migration of the copper atoms is much higher than that of the nickel atoms (there is a pronounced Kirkendall effect) and, with polycrystalline specimens, surface diffusion of copper over the nickel crystallites requires a lower activation energy than diffusion into the bulk of the crystallites. Hence, the following model was proposed for the location of the phases in Cu-Ni films (S3), prepared by annealing successively deposited layers at 200°C in vacuum, which was consistent with the experimental data on the work function. 

The Pt-Au films were not used in catalysis, but the chemisorption of CO was studied. The work function of Pt was only raised by 0.03 eV and there was no change with the alloys after short exposures to CO. It was therefore not possible to titrate the Pt content of the surface with CO in the same way as hydrogen was used with Cu-Ni alloy films (2). Long-term exposure of the films to 10 5-10-4 Torr CO at 20°C for periods up to four days caused the work function of the alloys to increase slowly Fig. 31. After 16 hr this increase was more evident in the Pt-rich region, but the effect was observed on the Au-rich regions after longer exposures. The effect was accelerated if the films were maintained at 100°C. These results were cited as direct evidence for the enrichment of the surface with platinum... 

W.M.H. Sachtler and R. Jongpier. The Surface of Copper-Nickel Alloy Films. II. Phase Equilibrium and Distribution and Their Implications for Work Function, Chemisorption, and Catalysis. J. Catal. 4 665 (1965). 

M. Anpo, M. Kitano, K. Tsujimaru, Decomposition of water in the separate evolution of hydrogen and oxygen using visible light-responsive Ti02 thin film photocatalysts Effect of the work function of the substrates on the yield of the reaction Applied Catalysis A General, 314,179-183, (2006). 

---