Carbon nanotube-based flexible biocathode for enzymatic biofuel cells by spray coating

Enzymatic biofuel cells are emerging technologies which gain a lot of interest as a power source for implantable devices. Effective enzyme wiring and simplification of the cell architecture are the main limitations of the fuel cell development nowadays. In the present study, spray coating was used as a reliable process to produce flexible biocathodes. That was achieved through spray coating of a conductive ink formulated by surfactant assisted carbon nanotubes dispersion. A thin continuous layer of carbon nanotubes (CNTs) was successfully coated on top of a gas diffusion layer paper. The film thickness was modulated by varying the CNT load in the ink and the number of deposited layers. It varied between 1 and 7.8 tun for a number of deposited layers between 5 and 100. Laccase enzyme was then wired to printed CNT electrodes thanks to the host-guest interaction between the hydrophobic pocket of laccase and pyrene-adamantane. Electrochemical investigations showed that laccase was effectively wired to the CNTs and presented a favorable orientation toward oxygen reduction. The biocathode current density was dependent of the number of deposited CNT layers and reached an optimum at 170 mu A cm(-2) for 50 deposited layers.