Glucose biofuel cells using the two-step reduction reaction of bienzyme structure as cathodic catalyst

Glucose oxidase (GOx) and horseradish peroxidase (HRP) based bienzymes are entrapped in a polyethylenimine (PEI) matrix and then immobilized onto a substrate consisting of carbon nanotube (CNT) and pyrene boronic acid (PBA) (CNT/PBA/[HRP/PEI/GOx]). This structure is considered as the cathodic catalyst for the glucose biofuel cell (GBFC). According to the performance evaluations of the catalyst, the catalytic activity for the oxygen reduction reaction (ORR) is improved because of the bienzyme entrapped well in PEI, and also, because the CNT/PBA substrate promotes electron transfer by the formation of π–π stacking and the reduction of the electron transfer pathway distance. The high ORR reaction rate (38.7 μA cm⁻² in the injection of 5 mM glucose) is clear evidence of an excellent catalyst. In addition, when the catalyst is adopted for the operation of a membrane GBFC, a high-power density (77.9 ± 2.3 μW cm⁻²) is achieved, as well as good storage stability (81% of its initial activity even after 4 weeks) and a high glucose consumption rate (8.7 ± 0.2% from its initial concentration during 7 operating hours). Alternatively, when the catalyst is used for the membraneless GBFC operation, a relatively high-power density of 18 μW cm⁻² is also obtained.