Fabrication of highly effective hybrid biofuel cell based on integral colloidal platinum and bilirubin oxidase on gold support

Abstract

A hybrid biofuel cell (HBFC) is explored as a low-cost alternative to abiotic and enzymatic biofuel cells. Here the HBFC provides an enzymeless approach for the fabrication of the anodic electrode while employing an enzymatic approach for the fabrication of the cathodic electrode to develop energy harvesting platform to power bioelectronic devices. The anode employed 250 μm braided gold wire modified with colloidal platinum (Au-co-Pt) and bilirubin oxidase (BODx) modified gold coated Buckypaper (BP-Au-BODx) cathode. The functionalization of the gold coated multi-walled carbon nanotube (MWCNT) structures of the BP electrodes is achieved by 3-mercaptopropionic acid surface modification to possess negatively charged carboxylic groups and subsequently followed by EDC/Sulfo-NHS (1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride and N-Hydroxysulfosuccinimide) crosslinking with BODx. The integration of the BODx and gold coated MWCNTs is evaluated for bioelectrocatalytic activity. The Au-co-Pt and BP-Au-BODx exhibited excellent electrocatalytic activity towards glucose oxidation with a linear dynamic range up to 20 mM glucose and molecular oxygen reduction, respectively. The HBFC demonstrated excellent performance with the largest open circuit voltages of 0.735 V and power density of 46.31 μW/cm² in 3 mM glucose. In addition, the HBFC operating on 3 mM glucose exhibited excellent uninterrupted operational stability while continuously powering a small electronic device. These results provide great opportunities for implementing this simple but efficient HBFC to harvest the biochemical energy of target fuel(s) in diverse medical and environmental applications.

Figure 1

Schematic diagram of the platinization of 3-strand braided anode and optical image of the as-platinized 3-strand braided Au anode.

Figure 2

(A) Cyclic voltammograms (CVs) of braided Au-co-Pt wire anode in (a) 10 mM PBS solution and (b-h) 1, 3, 5, 7, 10, 15, and 20 mM glucose (pH = 7.4) and the braided Au wire in the presence of (i) 10 mM PBS solution and (j) 1 mM glucose (pH = 7.4). (B) Cyclic voltammograms (CVs) of braided Au-co-Pt wire anode in various concentrations of H₂SO₄ (0.2, 0.4, 0.6, 0.8, 1.0 and 1.2 N). The scan rate was 25 mV s⁻¹. All CVs were performed at room temperature.

Figure 3

Scanning electron microscopy (SEM) images of (A) Au wire, (B) Au-co-Pt enzymeless anode and (C) high-resolution SEM image of Au-co-Pt enzymeless anode. SEM image of (D) high-resolution SEM image of Au-co-Pt after characterization in glucose solution.

Figure 4

Schematic illustration of surface modification of Au coated Buckypaper electrode with bilirubin oxidase to form the BP-Au-BODx biocathode for the HBFC.

Figure 5

Representative cyclic voltammograms for BP-Au-BODx electrode without oxygen (A) and in the presence of saturated oxygen (B) in 10 mM PBS solution (pH = 7.4) at 25 mV s⁻¹. All CVs were performed at room temperature.

Figure 6

Representative polarization (solid lines) and power curves (dashed lines) obtained from 3-strand braided Au-co-Pt| BODx HBFC in the presence of various glucose concentrations (1, 3, 5, 7, 10, 15, 20 mM) generated from Au-co-Pt anode and BP-Au-BODx cathode.

Figure 7

Peak power density against glucose concentration (1, 3, 5, 7, 10, 15, 20 mM) for the HBFC.

Figure 8

Chronoamperometric profiles of BOD biocathode (top curve) and colloidal Pt anode (bottom curve) characterized using a bipotentiostat in phosphate buffer. Oxygen was purged into the phosphate buffer at t = 0. At t = 200 s, glucose was injected to result in a final glucose concentration of 5 mM. Oxygen purging was stopped at t = 400 s.

Figure 9

(A) Circuit schematic of charge pump based amplifier circuit, (B) Powering of a red LED using integrated HBFC-charge pump based voltage amplifier circuit, and (C) power curve of HBFC.