Industrial solid state oxygen sensors, using fully stabilized zirconia as electrolyte, were modified and used to split water vapor, mixed with inert gas. Such conditions were chosen for simulating the tritium removal from the ceramic breeder materials in solid blanket fusion reactors. The single cell performances were investigated at 973 K and 200 cm3/min flow rate using argon/water vapor mixtures ranging from 100 to 700 vpm. The splitting efficiency was evaluated at 80%; steady state conditions were reached in a few minutes.