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Physical Chemistry 3: — Chemical Kinetics — - Christian-Albrechts ...

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10.2 <strong>Kinetics</strong> of heterogeneous reactions (surface reactions) 222<br />

10.2.4 Surface Diffusion<br />

I<br />

Figure 10.5: Surface Diffusion.<br />

I<br />

Diffusion is an activated process:<br />

µ<br />

= 0 exp − ∆ <br />

<br />

<br />

∆ = energy barrier of jump of adsorbate from one site to another.<br />

(10.51)<br />

I<br />

Fick’s 2nd law:<br />

( )<br />

<br />

= × 2 ( )<br />

2 (10.52)<br />

I<br />

Einstein’s diffusion law:<br />

• 1D:<br />

∆ 2 =2 (10.53)<br />

• 2D:<br />

∆ 2 =4 (10.54)

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