Mechanism of hydrogen oxidation on a platinum-loaded gas diusion electrode

The mechanism of hydrogen oxidation on a platinum-loaded gas-diusion electrode has been in-vestigated. Experimental potential–current curves, especially in the low overpotential range, have been measured for H2–N2 mixtures with a small content of hydrogen and for pure H2: Theoretical relations have also been presented. Comparing the experimental and theoretical relations, it is concluded that the hydrogen oxidation occurs according to the Volmer–Tafel mechanism. The re-activity of the electrode has a large eect on the kinetic parameters for hydrogen oxidation. The limiting current is determined by diusion of hydrogen for a very reactive gas diusion electrode and by the Tafel reaction for a gas diusion electrode with a low reactivity. The transfer coecient for the Volmer reaction aV is 0.5 and i0;V=i0;T 0:1 for a very reactive gas diusion electrode. aV increases and i0;V=i0;T ratio decreases with decreasing reactivity of the gas diusion electrode. 1