Discarge process of dioxigen on metal surface

Chicco83 · science forum beginner Joined: 27 Jun 2006 Posts: 2

In the fuel cells H2/air, methanol/air, Zn/air etc., the air is
fluxed at the negative electrode to allow the discharge of
dioxygen. In order to obtain high current density, appropriate
catalyst (for example Cobalt-porphyrin on carbon and noble
metal) are involved to obtain high current density.
In fact, the rate of discharge of dioxygen on the surface of
a generic metal is, generally, slow.

My questions are:

1- What are the elementary semi-reactions that taken part in the
complete reduction process of dioxygen on the generic metal
surface?

2-What of these estabilisches the limiting step?

Thanks all.

Google