Insight into why the Langmuir–Hinshelwood mechanism is generally preferred

In heterogeneous catalysis, the two main reaction mechanisms which have been proposed are the Langmuir–Hinshelwood and the Eley–Rideal. For the vast majority of surface catalytic reactions, it has been accepted that the Langmuir–Hinshelwood mechanism is preferred. In this study, we investigate catalytic CO oxidation on Pt(111). It is found that reaction barriers for Langmuir–Hinshelwood mechanisms actually tend to be higher than those for Eley–Rideal ones. An explanation is presented as to why it is still more probable for the reaction to proceed via the Langmuir–Hinshelwood mechanism, despite its higher reaction barrier.