Maximizing the enzyme immobilization of enzymatic glucose biofuel cells through hierarchically structured reduced graphene oxide

The number of immobilized glucose oxidase (GOx) molecules is considerably increased by the structural modification of reduced graphene oxide (rGO), and the performance of enzymatic biofuel cells (EBFCs) is positively affected by the modification process. To do this, new rGO with three-dimensional open porous structure is formed by spray freeze drying method (sprGO), while tetrathiafulvalene (TTF) as mediator, and GOx are sequentially immobilized onto sprGO. To improve the loading amount of catalyst, rGO structure is modified to open porous sprGO structure possessing numerous anchoring sites, after which gelatin film crosslinked by glutaraldehyde is fabricated onto sprGO to prevent any losses of other components (sprGO/[TTF-GOx]/crosslinked-gelatin). Specific surface area and charge transfer resistance of sprGO are quantitatively measured, and the actual amount of immobilized GOx and the performance of EBFC using this catalyst are electrochemically examined. With this, it is found that the amount of GOx immobilized in sprGO/[TTF-GOx]/crosslinked-gelatin is twice better that in rGO/[TTF-GOx]/crosslinked-gelatin. More specifically, EBFC using this catalyst shows open circuit voltage of 0.85 V and maximum power density of 380 μW/cm², and this is 1.4 times better than that using rGO/[TTF-GOx]/crosslinked-gelatin. These results indicate that the amount of immobilized GOx strongly affects the performance capabilities of EBFCs.