Study On Carbon Nanotubes-based Enzyme Electrodes For Enzymatic Biofuel Cells

Enzymatic biofuel cells (EBFC), one kind of effective devices which couldconvert chemical energy into electrical energy directly with enzymes asbiocatalysts, have some unique advantages such as high availability of fuels, lowcost, good biocompatibility, more moderate operation temperature, higherconversion efficiency and more environmental friendly compared with traditionalfuel cells. Therefore, they have the potential to be used as the power sources ofheart pacemakers and planted biosensors and have attracted considerable researchattention all over the world. However, low power density and short lifetime aretwo major problems that hinder the further practical applications of EBFC.Suitable materials and effective methods for the immobilization of enzymes andmediators may be the right solution to the two major problems. In this thesis, eitherthe complex of carbon nanotubes (CNTs) and graphene oxide (GO) or thehomemade novel ultrashort and open nitrogen-doped carbon nanotubes (SNCNTs) wasused to construct EBFC. The performance of the prepared enzyme electrodes andconstructed EBFC was fully studied. The main points are summarized as follows:(1) CNTs and GO were noncovalent-functionalized with1-pyrene-carboxaldehyde (PA) through the π-π stack to prepare PA-CNTs and PA-GO. Theobtained PA-CNTs and PA-GO were used to immobilize the mediatoraminoferrocene (NH2Fc) and biocatalyst glucose oxidase (GOD), respectively. Theaimed bioanode ((Fc-PA-CNTs/GOD-PA-GO)/GC electrode) showed much highercurrent density for the electrooxidation of glucose than those of the other twobioanodes ((GOD-PA-CNTs/Fc-PA-CNTs)/GC electrode and (Fc-PA-GO/GOD-PA-GO)/GC electrode). The resulted glucose/O2EBFC had an open circuitpotential (Vo c) and short circuit current density (is c) of0.73V and91.5μA cm-2,respectively. The obtained maximum power density was21.2μW cm-2.(2) Taking halloysite nanotubes (HNTs) as the template, ultrashort and opennitrogen-doped carbon nanotubes (SNCNTs) with big inner diameter wassynthesized by pyrolysis of polydopamine (PDA) wrapped halloysite nanotubes(HNTs). Fe(CN)63-/4-was used as the electrochemical probe to evaluate theelectrochemical properties of the SNCNTs-based electrode. The SNCNTs-based electrode showed excellent electrocatalytic ability toward the redox of hydrogenperoxide (H2O2) and could be used to detect H2O2. SNCNTs was also used toimmobilize GOD, and a new electrochemical glucose sensor with good analyticalperformance was developed. The results showed the outstanding electrochemicalproperies of SNCNTs, suggesting a promising application in enzymatic biofuel cellsbased on SNCNTs.(3) Enzyme bioanode and corresponding glucose/O2biofuel cell wereprepared based on the obtained novel nitrogen-doped carbon nanotubes SNCNTs.The Vo cand is cof the assembled EBFC were0.72V and1.15mA cm-2, and themaximum power density is246μW cm-2at0.29V. After continuous operation for80h, the developed EBFC didn’t show any decrease in the open circuit potential,suggesting the good operating stability.