Reaction rate and adsorption energy

For technological applications it is important to find a good catalyst at which the reaction proceeds with a high rate. If the reaction involves an 

The Gibbs energy of adsorption on a particular metal is difficult to measure, but it should be related to the strength jEm-H of the corre- 

Of course, changing the electrode material entails more than just changing the adsorption energy, so we cannot expect more than a rough correlation. Nevertheless, volcano plots are observed for several reactions involving adsorbed intermediates. 

However, a closer inspection of the experimental data reveals several differences. For ion-transfer reactions the transfer coefficient a can take on any value between zero and one, and varies with temperature in many cases. For outer-sphere electron-transfer reactions the transfer coefficient is always close to 1/2, and is independent of temperature. The behavior of electron-transfer reactions could be explained by the theory presented in Chapter 6, but this theory - at least in the form we have presented it - does not apply to ion transfer. It can, in fact, be extended into a model that encompasses both types of reactions [7], though not proton-transfer reactions, which are special because of the strong interaction of the proton with water and because of its small mass. 

While a treatment of this unified model for electron- and ion-transfer reactions is beyond the scope of this book, we can gain some insight into the nature of electrochemical reactions by looking at some of its results. In particular, this model makes it possible to calculate the potential-energy surface of a reaction. To understand the meaning of 

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The Sabatier principle deals with the relation between catalytic reaction rate and adsorption energies of surface reaction intermediates. A very useful relation often... 

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