POXC Laccase from Pleurotus ostreatus: A High-Performance Multicopper Enzyme for Direct Oxygen Reduction Reaction Operating in a Proton-Exchange Membrane Fuel Cell

In this work, POXC, a laccase from Pleurotus ostreatus, was immobilized on carbon nanotubes (CNTs) modified by electro-grafting anthraquinone and naphthoate diazonium salts. Thanks to a favorable interaction between laccase and covalently modified CNTs, this laccase exhibits high-potential/high-current oxygen reduction reaction (ORR) performances, surpassing the performances of the well-known laccase from Trametes versi-color (TvLAC) immobilized on the same nanostructured electrodes. Furthermore, immobilized POXC demonstrates high ORR activity over a wide range of pH (2 to 8), being also highly active at a gas-diffusion electrode. Finally, owing to these unique performances, this enzyme was able to operate at the interface of the microporous layer, humidified air and a polymer electrolyte, that is, Nafion (R), in a conventional H-2/air proton-exchange membrane fuel.