Laccase electrodes based on the combination of single-walled carbon nanotubes and redox layered double hydroxides: Towards the development of biocathode for biofuel cells

Single-walled carbon nanotubes (SWCNT) were combined with layered double hydroxides (LDH) intercalated with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) diammonium salt [ZnCr-ABTS] to entrap and electrically connect laccase enzyme. The resulting laccase electrodes exhibited an electro-enzymatic activity for O2 reduction. To improve this electrocatalytic activity, varying SWCNT quantities and loading methods were tested to optimize the configuration of the laccase electrodes. Furthermore, the resulting bioelectrode was successfully used as a biocathode for the elaboration of a membrane-less glucose/air biofuel cell. In 0.1 M phosphate buffer (PBS) of pH 6.0, containing glucose (5 mM) under ambient conditions, the assembled biofuel cell yielded a maximum power density of 18 μW cm−2 at a cell voltage of 0.3 V whereas this power decreased to 8.3 μW cm−2 for a biofuel cell based on the identical biocathode setup without SWCNT.