Usefulness and Performance Comparison of Complex Enzyme-type Biofuel Cell Using Electrode Modified with Two DET-type Enzymes by Covalent Bonding

Abstract

The demand for enzymatic biofuel cells (EBFCs) as power sources or auxiliary power sources for small devices is expected to increase in the near future. EBFCs have advanced properties and do not require a separator, depending on the substrate specificity of the enzyme. Two direct electron transfer (DET)-type enzymes were used to modify anodes (length 5 mm, width 4 mm) by a chemical modification method using a condensation agent. The DET-type enzymes used in this study were pyrroloquinoline quinone-dependent glucose dehydrogenase (PQQ-GDH) with glucose as a reaction substrate and fructose dehydrogenase (FDH) using fructose as a reaction substrate. Carboxyl groups were attached to multi-walled carbon nanotubes (MWCNTs) that act as catalyst carriers, activated to other functional groups, and reacted with the amino groups of the enzyme by the condensation agent to form covalent bonds. As a result, the upper limit of the concentration, considered to be the reaction limit, was raised as compared with that of EBFC modified with only one kind of enzyme for each electrode prepared by the same process. The output voltage was 0.155 V, and the maximum power density was 80.08 μW/cm2. Also the deterioration characteristics were confirmed with the passage of time for EBFC-Z; the maximum power density was almost unchanged for three months, and output reduction due to the passage of time was not observed.