Membraneless biofuel cells using new cathodic catalyst including hemin bonded with amine functionalized carbon nanotube and glucose oxidase sandwiched by poly(dimethyl-diallylammonium chloride)

A new cathodic catalyst is developed for improving the performance of membraneless enzymatic biofuel cell (EBC) by enhancing overall oxygen reduction reaction (ORR). In this catalyst, both hemin and glucose oxidase (GOx) are considered as enzymatic catalysts to facilitate H₂O₂ reduction reaction (HRR) and partial oxygen reduction reaction (PORR), respectively. Hemin is attached to amine group functionalized carbon nanotube (Amine-CNT) to form amide bond, and GOx is conjugated with two poly(dimethyl-diallylammonium chloride) (PDDA) layers to form sandwich-like structure. As a result, [Amine-CNT/Hemin]/PDDA/GOx/PDDA catalyst is completed. This catalyst plays a role in reducing the amount of GOx leached out and preserving the mass transfer of fuels, and finally, increasing the catalytic activity for cathodic reactions. According to electrochemical estimation, its onset potential reaches 0.4 V vs. Ag/AgCl and current density significantly increases to 323 μA cm⁻². When the performance of membraneless EBC adopting this catalyst is measured, maximum power density is 24.1 ± 0.61 μW cm⁻² and its activity preserves 82.1% after four weeks. This excellent result is because PORR and HRR are promoted by the rigid connection of GOx and hemin, which is mainly induced by the sandwich effect of GOx by PDDA layers.