Construction and Performance of a New Bioanode for Biofuel Cells

Acid-treated carbon nanotubes (CNTs) were functionalized by beta-cyclodextrin (CD) through the van der Waals force between them. It is well-known that CD is toroidal in shape with a hydrophobic inner cavity and a hydrophilic exterior. Based on the recognition of CD to ferrocene (Fe), a water-soluble complex, CNTs-beta-CD-Fc, was prepared. Glucose oxidase (GOD) was mixed with CNTs-beta-CD-Fc and crosslinked with glutaraldehyde to form enzyme polymer. Then the GOD/CNTs-beta-CD-Fc composite was coated on the glassy carbon (GC) electrode and the GOD/CNTs-beta-CD-Fc/GC bioanode was obtained. The prepared CNTs-beta-CD and CNTs-beta-CD-Fc were characterized by thermal gravimeritric analysis, fourier transform infrared spectroscopy and transmission electron microscopy. The electrocatalytic properties of the GOD/CNTs-beta-CD-Fc/GC bioanode towards glucose oxidation were investigated by cyclic voltammetry. The results showed that under the same experimental conditions, the GOD/CNTs-beta-CD/GC electrode (without Fe) had almost no catalytic currents for glucose oxidation and the GOD/CNTs-beta-CD-Fc/GC bioanode had higher electrocatalytic activity towards glucose oxidation than the GOD/CNTs-Fc/GC electrode. The long-term cycle stability of the developed GOD/CNTs-beta-CD-Fc/GC bioanode was also evaluated by cyclic voltammetry and the results showed that the GOD/CNTs-beta-CD-Fc/GC bioanode had much better stability than the GOD/CNTs-Fc/GC electrode. Taking the commercial E-TEK Pt/C modified GC electrode as the cathode, the maximum power density of the glucose/O-2 biofuel cell (EBFC) based on the GOD/CNTs-beta-CD-Fc/GC anode was 33 mu W.cm(-2) (at 0.18 V), almost 3 times higher than that of the EBFC based on the GOD/CNTs-Fc/GC anode (11.7 mu W.cm(-2) at 0.16 V). The stability of the developed EBFC was also investigated by monitoring the change of the open circuit potential (OCP) of EBFC. After continuous operation for 9 h, the developed EBFC (the GOD/CNTs-beta-CD-Fc/GC electrode as the bioanode) remained 92% of initial OCP, suggesting the good operating stability. The proposed strategy for bioanode preparation may provide a new way for the development of glucose/O-2 EBFC with good perfomance and high stability.