Development of a printable laccase-based biocathode for fuel cell applications

Laccases belong to the family of blue multicopper oxidases, which catalyze the four-electron reduction of dioxygen to water concomitantly through the oxidation of phenolic and other aromatic compounds. They are potential enzymes in many applications including biofuel cells to produce electricity through chemical reactions. We have tested here the incorporation of a high redox potential laccase from Trametes hirsuta in different types of conducting inks to produce dry printed enzyme electrode layers. ABTS was used as the redox mediator to shuttle the electrons between the surface of the cathodic electrode and the enzyme active sites. Our results demonstrate that the dry printed layers maintained their enzymatic activity even after several months. Furthermore, fuel cell prototypes could be constructed utilising an optimized printed laccase–ABTS layer as the cathode, and printed Zn layer as the anode. Under humidity controlled conditions, a cell voltage between 0.8 and 0.6 V could be maintained for several days under a 2.2 kΩ load. In addition, a corresponding stand-alone cell could be constructed where the cell voltage was maintained for 15 h under a load. These results offer a good starting point for further development of mass-producible, completely enzymatic printed biofuel cells.