Functionalized and Enhanced HB Pencil Graphite as Bioanode for Glucose-O2 Biofuel Cell

Herein, a novel, low-cost and readily available HB pencil graphite (PG), as bioanode for enzymatic biofuel cell, is presented. The surface area of the PG is substantially increased by coating carboxylated multiwalled carbon nanotube through the dipping method followed by its covalent immobilization with glucose oxidase enzyme to fabricate the bioanode. The surface morphology of fabricated bioanode is characterized by scanning electron microscopy, and the electrochemical studies are performed through linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. The results reveal that the fabricated bioanode shows good direct electron transfer characteristics between the dynamic site of the enzyme and the terminal surface of electrode. Approximately, 1.23 × 10
^-11
mol · cm
^-2
of glucose oxidase is found to anchor on the fabricated bioanode with significant electron transfer rate of 3.2 s
^-1
. Furthermore, the catalytic activity of fabricated bioanode is enhanced with increase in the glucose concentration, and a hyperbolic Michaelis-Menten kinetics is observed with Km value of 5.5 mM and maximum current density of 4605 μA·cm
^-2
at 40-mM saturated glucose concentration. Finally, the fabricated bioanode exhibits stability with reasonably good retention of biocatalytic activity, thus establishing HB PG as promising bioanode material for enzymatic biofuel cell.