Hydrogenases are the key enzymes for hydrogen metabolism in many microorganisms. Due to the high efficiency and specificity they developed for H2 oxidation, they have been recently used as biocatalysts for an efficient H2/O2 biofuel cell. In this work we explore new properties of an O2-, CO- and T degrees-resistant hydrogenase. Enzyme immobilization on carbon nanotube modified electrodes is studied and optimized for long-term stabilization of the direct hydrogen catalytic oxidation process. The role of co-immobilized redox mediator is finally discussed in view of H2/O2 fuel cell performance enhancement.