Direct hybrid glucose–oxygen enzymatic fuel cell based on tetrathiafulvalene–tetracyanoquinodimethane charge transfer complex as anodic mediator

TTF–TCNQ has been used for the first time as a mediator in a direct glucose fuel cell operating on gas-phase oxygen. It has been shown that TTF–TCNQ forms highly irregular porous structure, which emphasizes the importance of optimization of mass transport and kinetic resistance in the catalyst layer. Kinetics resistance can be optimized by variation of the mediator and/or enzyme loading, while mass transport resistance mainly by the variation of other structural parameters such as electrode thickness. The optimized anode reached limiting current densities of nearly 400 μA cm−2 in presence of 5 mM glucose under rotation. The enzymatic fuel cell exhibited unexpectedly high OCV values (up to 0.99 V), which were tentatively ascribed to different pH conditions at the anode and the cathode. OCV was influenced by glucose crossover and was decreasing with an increase of glucose concentration or flow rate. Although the performance of the fuel cell is limited by the enzymatic anode, the long-term stability of the fuel cell is mainly influenced by the Pt cathode, while the enzymatic anode has higher stability. The fuel cell delivered power densities up to 120 μW cm−2 in presence of 5 mM glucose, depending on the glucose flow rate.

► Modular hybrid fuel cell with enzymatic anode and Pt cathode, separated by Nafion.
► 3D-enzymatic anode based on TTF–TCNQ and glucose oxidase.
► High power density at 5 mM glucose, operation with oxygen.
► Limited long-term stability due to change of pH at cathode side.