A Tandem Solar Biofuel Cell: Harnessing Energy from Light and Biofuels

Abstract

We report on a photobioelectrochemical fuel cell consisting of a glucose-oxidase-modified BiFeO₃ photobiocathode and a quantum-dot-sensitized inverse opal TiO₂ photobioanode linked to FAD glucose dehydrogenase via a redox polymer. Both photobioelectrodes are driven by enzymatic glucose conversion. Whereas the photobioanode can collect electrons from sugar oxidation at rather low potential, the photobiocathode shows reduction currents at rather high potential. The electrodes can be arranged in a sandwich-like manner due to the semi-transparent nature of BiFeO₃ , which also guarantees a simultaneous excitation of the photobioanode when illuminated via the cathode side. This tandem cell can generate electricity under illumination and in the presence of glucose and provides an exceptionally high OCV of about 1 V. The developed semi-artificial system has significant implications for the integration of biocatalysts in photoactive entities for bioenergetic purposes, and it opens up a new path toward generation of electricity from sunlight and (bio)fuels.

Keywords: biocatalysis; biofuel cells; energy harvesting; photocatalysis; photoelectrochemistry.

Scheme 1

Illustration of the photobioelectrochemical tandem cell consisting of a BiFeO₃|GOx photobiocathode and an IO‐TiO₂|PbS|P_Os|FAD‐GDH photobioanode, and the proposed electron transfer steps of the signal chain under illumination and in the presence of glucose. PBD ID GOx: 1CF3, ^[30] PDB ID FAD‐GDH: 4YNT. ^[31]

Figure 1

A) Cyclic voltammograms of pure FTO slides (a,b) and FTO|BiFeO₃ electrodes (c,d) in the presence (b,c) and absence (a,d) of 2.5 mM H₂O₂ in the dark (100 mV s⁻¹). Inset: SEM image of a BiFeO₃ electrode with a 10 000‐fold magnification. B) Chopped‐light voltammetry of a BiFeO₃ electrode in the presence and absence of 2.5 mM H₂O₂ (100 mW cm⁻²; 10 mV s⁻¹). C) Photocurrent density change ΔI of a BiFeO₃ electrode before and after addition of different H₂O₂ concentrations (100 mW cm⁻²; 0.2 V vs. Ag/AgCl, 1 M KCl). Inset: wavelength‐dependent photocurrent response (black points) and UV/Vis spectrum (blue line) of a BiFeO₃ electrode (0.2 V vs. Ag/AgCl, 1 M KCl).

Figure 2

Chopped‐light voltammetry of a BiFeO₃|GOx electrode in the presence and absence of 10 mM glucose (100 mW cm⁻²; potential vs. Ag/AgCl, 1 M KCl; 10 mV s⁻¹). Inset: photocurrent density change ΔI of a BiFeO₃|GOx electrode before and after addition of different glucose concentrations (100 mW cm⁻²; 0.2 V vs. Ag/AgCl, 1 M KCl).

Figure 3

A) Photocurrent response of an IO‐TiO₂|PbS|P_Os|FAD‐GDH electrode in the presence and absence of 100 mM glucose at different potentials (100 mW cm⁻²; potential vs. Ag/AgCl, 1 M KCl). B) Potentiometric measurement of the photobiocathode (a,b) and the photobioanode (c,d) in the presence (a,d) and absence (b,c) of glucose under illumination (100 mW cm⁻²; OCP vs. Ag/AgCl, 1 M KCl). C) Wavelength‐dependent photocurrent of an IO‐TiO₂|PbS|P_Os|FAD‐GDH electrode with unimpeded illumination (black curve) and by illumination through the BiFeO₃ (red curve) material (0 V vs. Ag/AgCl, 1 M KCl). Additionally, the UV/Vis spectrum of BiFeO₃ is shown.

Figure 4

Current and power density of the photobioelectrochemical tandem cell, consisting of an BiFeO₃|GOx photobiocathode and an IO‐TiO₂|PbS|P_Os|FAD‐GDH photobioanode in the presence (solid lines) and absence (dotted lines) of 100 mM glucose and under illumination. The tandem cell is arranged in a sandwich‐like manner, so that the photoexcitation of both electrodes is realized by lighting through the semi‐transparent photobiocathode (100 mW cm⁻²; 5 mV s⁻¹).