title: Prolongation of electrode lifetime in biofuel cells by periodic enzyme renewal.
abstract: Enzymatically catalyzed biofuel cells show unique specificity and promise high power densities, but suffer from a limited lifetime due to enzyme deactivation. In the present work, we demonstrate a novel concept to extend the lifetime of a laccase-catalyzed oxygen reduction cathode in which we decouple the electrode lifetime from the limited enzyme lifetime by a regular resupply of fresh enzymes. Thereto, the adsorption behavior of laccase from Trametes versicolor to buckypaper electrode material, as well as its time-dependent deactivation characteristics, has been investigated. Laccase shows a Langmuir-type adsorption to the carbon nanotube-based buckypaper electrodes, with a mean residence time of 2 days per molecule. In a citrate buffer of pH 5, laccase does not show any deactivation at room temperature for 2 days and exhibits a half-life of 9 days. In a long-term experiment, the laccase electrodes were operated at a constant galvanostatic load. The laccase-containing catholyte was periodically exchanged against a freshly prepared one every second day to provide sufficient active enzymes in the catholyte for the replacement of desorbed inactive enzymes. Compared to a corresponding control experiment without catholyte exchange, this procedure resulted in a 2.5 times longer cathode lifetime of 19 ± 9 days in which the electrode showed a potential above 0.744 V vs. normal hydrogen electrode at 110 μA cm(-2). This clearly indicates the successful exchange of molecules by desorption and re-adsorption and is a first step toward the realization of a self-regenerating enzymatic biofuel cell in which enzyme-producing microorganisms are integrated into the electrode to continuously resupply fresh enzymes.
authors.affiliation: Laboratory for MEMS Applications, Department of Microsystems Engineering-IMTEK, University of Freiburg, Georges-Koehler-Allee 103, 79110, Freiburg, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Rubenwolf
authors.forename: S
authors.initials: S
authors.lastname: Sané
authors.forename: L
authors.initials: L
authors.lastname: Hussein
authors.forename: J
authors.initials: J
authors.lastname: Kestel
authors.forename: F
authors.initials: F
authors.lastname: von Stetten
authors.forename: G
authors.initials: G
authors.lastname: Urban
authors.forename: M
authors.initials: M
authors.lastname: Krueger
authors.forename: R
authors.initials: R
authors.lastname: Zengerle
authors.forename: S
authors.initials: S
authors.lastname: Kerzenmacher
mesh_terms: D001674:Bioelectric Energy Sources; D004566:Electrodes; D042845:Laccase / Q000378:metabolism*; D055672:Static Electricity; D013997:Time Factors; D055454:Trametes / Q000201:enzymology*
chemical_list: D042845:Laccase