| AVS 60th International Symposium and Exhibition | |
| Surface Science | Monday Sessions |
| Session SS-MoA |
| Session: | Metal Oxides: Reactivity and Catalysis |
| Presenter: | C.A. Wolcott, University of Washington |
| Authors: | C.A. Wolcott, University of Washington I.X. Green, University of Washington C.T. Campbell, University of Washington |
| Correspondent: | Click to Email |
Metal oxides represent an important class of materials whose interfacial properties play an important role in chemical sensors, catalysis, environmental science, biology, and many other fields [1]. This poster presents for the first time the direct measurement of the heat of adsorption and reaction of a molecular species on an oxide surface. The energetics of the adsorption and reaction of D2O with a Fe3O4 (111) surface were studied using single crystal adsorption calorimetry (SCAC). SCAC allows for the direct measurements of surface reaction heats by using a pulsed molecular beam, a thin sample, and a temperature transducer. A 4nm thick film of Fe3O4(111) was grown on a 1µm thick Pt(111) crystal using the method of Weiss and Ranke[1]. Following the work of Weiss et al. [2], water is expected to form three species on an Fe3O4 (111) surface. Initially water reacts and dissociates on the surface producing surface hydroxyls bound to iron sites and hydrogen bound to oxygen sites. Upon continued dosing some water is seen to adsorb molecularly on the surface before eventually forming multilayers. In the present work we explored the heat of adsorption of D2O as a function of both surface temperature and surface coverage using a pulsed molecular beam and a liquid nitrogen cryostat. By analyzing how the heat of adsorption changes as a function of temperature and coverage and correlating with the surface species observed by Weiss and others, heats of reaction for the formation of surface hydroxyls and molecular water on Fe3O4(111) are calculated. These results are compared with the heats measured indirectly by Weiss et al using TPD and UPS [2] and with DFT results [3].
[1] Weiss W., Ranke W., Progress in Surface Science, 70, 2002, 1.
[2] Joseph Y., Kuhrs C., Ranke W., Weiss W., Surface Science, 433, 1999, 114.
[3] Yang T., Wen X.D., Cao D.B, Li Y.W, Wang J.G., Huo C.F., J Fuel Chem Technol, 37 (4), 2009, 506.