Abstract
This study investigates the performance of pencil graphite (PG) electrodes to identify the grade of pencil most suitable as bioanode for enzymatic glucose biofuel cell. Pencils of H, 3H, 5H and B grades are selected for this study. The surfaces of different grade PGs are modified with carboxylic acid functionalized multi walled carbon nanotubes (COOH-MWCNT/PG), followed by immobilization with glucose oxidase (GOx) to fabricate the respecttive bioanodes (GOx/COOH-MWCNT/PG). Morphological and electrochemical characterizations are carried out using scanning electron microscopy, electrochemical impedance spectroscopy, cyclic voltammetry and energy dispersive X-ray spectroscopy. All tested PG electrodes exhibited positive results with variable response characteristics towards glucose oxidation reaction. B-grade PG bioanode is found to have the highest coverage of the deposited nanobiocomposite with the fastest electron transfer rate. The half-cell electrode assembly with this grade of PG recorded the highest current density of 4.25 mA cm-2 at physiological glucose conditions (5 mM glucose, pH 7.0). Enzymatic glucose biofuel cell assembled with B-grade PG bioanode and platinum cathode generated an open circuit potential of 149 mV and maximum power density of 0.789 µW cm−2 from 5 mM glucose at ambient conditions (25 ± 3◦C). The results obtained for B-grade PG bioanode are comparable to those of conventional carbon and glassy carbon electrodes, thus demonstrating its applicability to enzymatic glucose biofuel cells.
Highlights
Enzymatic glucose biofuel cells (EGBFCs) employ enzymes as catalysts which exhibit extremely specific electro-catalytic activities for biochemical and biological reactions [1]
This work demonstrates the application of modified pencil graphite (PG) of different grades as suitable bioanodes for enzymatic glucose biofuel cell (EGBFC)
Morphological characterization of tested PG of grades H, 3H, 5H, and B have indicated some variations in enzyme immobilization on the surface of PG, based on their composition and surface structure
Summary
Enzymatic glucose biofuel cells (EGBFCs) employ enzymes as catalysts which exhibit extremely specific electro-catalytic activities for biochemical and biological reactions [1]. The objective of the present research work is to evaluate the performance of various grades (H, 3H, 5H and B) of PG in order to identify the grade best suited for bioanode in EGBFC The surface of these grades of PG were modified first by dip coating of carboxylic acid functionalized multiwalled carbon nanotubes (COOH-MWCNT/PG) and by covalent immobilization of glucose oxidase (GOx) enzyme, forming GOx/COOH-MWCNT/PG electrode. Analytical grade chemicals and materials were procured from Sigma–Aldrich and used as received They include dibasic sodium phosphate (Na2HPO4), monobasic sodium phosphate (NaH2PO4), sodium hydroxide (NaOH), hydrogen chloride (HCl), 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC), acetone, potassium ferricyanide (K3[Fe(CN)6 ), dimethyl sulfoxide (DMSO), D-(+)-glucose, N-hydroxy succamide (NHS), p-benzoquinone (PBQ), carboxylic acid functionalized multiwalled carbon nanotubes, (COOH-MWCNT) with average diameter and length 9.5 nm and 1.5 μm. Morphological and elemental composition studies of fabricated PG based bioanodes were performed using scanning electron microscopy performed by Apreo SEM with an energy dispersive X-ray (EDX) instrument
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