Urgent: fuel cell modeling

gang

I am just starting to use fluent. And I am trying to model SOFC's temperature distribution. I got a problem in defining the reaction: 1. for cathode side, I am using pure o2 now 2. for anode, pure h2 is used.

and o2 reducing reaction takes place on cathode side. then ionic o will pass to anode and reacts with h2. SO by this nature, i want to define both reaction as surface reaction in the surface. but Fluent seems refuse me to define it as surface reaction. So what should I do for this, in order ro solve this problem.

Numerous thanks for you! Axiously and sincerely wanting for your reply!

VERY TRULY YOURS, GANG