Materials for energy production and storage: fuel cells and redox flow batteries

Stabilization and electrical contacting of redox enzymes with electrodes are fundamental requirements for the development of bioelectronics devices such as biosensors and EFCs. In the present work, we show that glucose oxidase (GOx) stability could be increased by immobilization with Nafion. The immobilization process affected GOx conformation but was not detrimental to its activity, which was maintained for over 120 days. The GOx/Nafion system was interfaced to a carbon cloth electrode and assembled in a prototype EFC fed with glucose. Polarization and power density curves demonstrated that GOx/Nafion system was able to generate power, exploiting a Nafion-assisted electron transfer process to the electrode. Our findings are consistent with the onset of pH-dependent conformational equilibrium for the enzyme secondary structure and its active site. Significantly, the protective effect by Nafion on the enzyme structure may be tuned by varying parameters such as pH, in order to fabricate durable EFCs with good performance in electricity and power production.