Electrochemical crystal hydrogen adsorption

FIGURE 12.4 Top Experimentally measured exchange current, log(io), for the HER over different metal surfaces plotted as a function of the calculated hydrogen chemisorption energy per atom, AE (top axis). Single crystal data are indicated by open symbols. Bottom The result of the simple kinetic model plotted as a function of the free energy for hydrogen adsorption, AGg, = AE + 0.24 eV. (Erom Nprskov, J. K. et al., J. Electrochem. Soc., 152, J23, 2005. With permission.)... 

Ross PN (1979) Structure sensitivity in the electrocatalytic properties of Pt. I. Hydrogen adsorption on low index single crystals and the role of steps. J Electrochem Soc 126 67-77... 

The adsorption and catalytic properties of Pd films supported on single-crystal metal snrfaces have received attention in snrface electrochemistry. As depicted in Fig. 3.3a electrochemical oxidation of hydrogen on a Au(lll)-Pd surface clearly revealed that this surface exhibits significant activity, while a pure gold surface is completely inactive [51]. Considering that the amount of Pd on Au(lll) is fairly small, this example highlights the importance of the surface and near-surface composition as well as the ability to tnne catalytic activity by changing the surface constituents. 

Fig. 8. Adsorption isotherms of hydrogen on [100] (O) and [111] ( ) planes of Pt mono-crystals. Dashed lines show theoretical curves assuming lateral interactions between surface H atoms (106. (Reprinted by permission of the publisher. The Electrochemical Society, Inc.)...

The first subdiscipline of chemistry in which the QCM was widely applied was electrochemistry. In 1992 Buttry and Ward published a review entitled Measurement of interfacial processes at electrode surfaces with the electrochemical quartz crystal microbalance , with 133 references [8]. This is the most widely cited paper on quartz crystal microbalances. After presenting the basic principles of AT-cut quartz resonators, the authors discuss the experimental aspects and relation of electrochemical parameters to QCM frequency changes. In their review of the investigation of thin films, they discuss electrodeposition of metals, dissolution of metal films, electrovalency measurements of anion adsorption, hydrogen absorption in metal films, bubble formation, and self-assembled monolayers. The review concludes with a brief section on redox and conducting polymer films. 

Cyclic voltammetry (CV) is one of the most widely used electrochemical techniques for acquiring qualitative information about electrochemical reactions. Measurement using cyclic voltammetry can rapidly provide considerable information about the thermodynamics of redox processes and the kinetics of heterogeneous electron-transfer reactions, as well as coupled chemical adsorption and reactions. Cyclic voltammetry is often the first experiment performed in an electroanalytical study. In particular, it can rapidly reveal the locations of the redox potentials of the electroactive species. CV is also used to measure the electrochemical surface area (ECSA, m /g catalyst) of electrocatalysts (e.g., Pt/C catalyst) in a three-electrode system with a catalyst coated glass carbon disk electrode as a working electrode [52]. Figure 21.9 shows a typical CV curve on Pt/C. Peaks 1 and 2 correspond to hydrogen electroadsorption on Pt(lOO) and Pt(l 11) crystal surfaces, respectively. The H2 electroadsorption can be expressed as Equation 21.35 ... 

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