A shriveled rectangular carbon tube with the concave surface for high-performance enzymatic glucose/O biofuel cells.

In this study, a novel carbon tube was prepared by carbonizing a rectangular polypyrrole (RPPy) tube at a high temperature for the construction of enzymatic biofuel cells with high performance. SEM and TEM images clearly showed that the initial PPy presented a rectangular tube shape, while the carbonized PPy became a shriveled rectangular tube with a concave surface, which might be beneficial for enzyme immobilization and electrochemical applications. The glucose oxidase (GOx)- or laccase (Lac)-modified electrodes based on carbonized RPPy exhibited excellent bioelectrochemical performance. In addition, a biofuel cell (GOx, glucose/O, Lac) was assembled, and the open-circuit voltage reached 1.16 V. The maximum power density was measured to 0.350 mW cm, which correlated to the gravimetric power density of 0.265 mW mg (per mg of GOx) at 0.85 V. The constant-current discharge method was used to further evaluate the continuous discharge capacity. The discharge time reached 49.9 h at a discharge current of 0.2 mA before the voltage was lower than 0.8 V. Furthermore, three of the fabricated biofuel cells in series were able to continually light up a white light-emitting diode (LED) whose turn-on voltage was ca. 2.4 V for more than 48 h. This study suggests that carbonized conducting polymers may become a useful electrode material for the development of enzymatic biofuel cells.