Oxygen transport through laccase biocathodes for a membrane-less glucose/O2 biofuel cell

The present study reports the development of operational membrane-less glucose/O2 biofuel cell based on oxygen contactor. Glucose oxidation was performed by glucose oxidase (GOx) co-immobilized with the mediator 8-hydroxyquinoline-5-sulfonic acid hydrate (HQS) at the anode, whereas oxygen was reduced by laccase co-immobilized with 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt (ABTS2−) at the cathode. Both enzymes and mediators were immobilized within electropolymerized polypyrrole polymers.Nevertheless, this system is limited by the secondary reaction of O2 electro-reduction at the anode that reduces the electron flow through the anode and thus the output voltage. In order to avoid the loss of current at the anode in glucose/O2 biofuel cell, we developed a strategy to supply dissolved oxygen separate from the electrolyte. Porous carbon tubes were used as electrodes and modified on the external surface by the couple enzyme/mediator. The inside of the cathode tube was continuously supplied with saturated dioxygen solution diffusing from the inner to the external surface of the porous tube. The assembled biofuel cell was studied under nitrogen at 37 °C in phosphate buffer at pH 5.0 and 7.0. The maximum power density reached 27 μW cm−2 at a cell voltage of 0.25 V at pH 5.0 with 10 mM glucose. The power density was twice as high as compared to the same system with oxygen bubbling directly in the cell.