Peroxidase biocathodes for a biofuel cell development

Abstract

In terms of sustainable energy production, enzymatic biofuel cells are attractive for a number of special applications, such as disposable implantable power suppliers for medical sensor-transmitters and drug delivery/activator systems and self-powered enzyme-based biosensors; they offer practical advantages of using abundant organic raw materials as biofuels for clean and sustainable energy production. In this paper we discuss what power densities can be expected from enzymatic biofuel cells and what are the possibilities and limits for their optimization. As example, in this work, the designed hybrid biofuel cell formed by the battery type Zn anode and the biocathode, comprising horseradish peroxidase (HRP) immobilized on graphite and utilizing H2O2 as an oxidizer, is considered. The cell yields the open circuit voltage Voc of 1.68 and 1.57 V and the short-circuit current density isc of 800 μA cm−2 at pH 6 and 580 μA cm−2 at pH 7.45 in quiescent solutions. The biofuel cell operated at 1.5 V for 6 days; the maximum power density of the cell was 98 μW cm−2 at 0.6 V and pH 6. When coupled to the H2O2-producing glucose oxidizing enzymes (glucose oxidase or pyranose oxidase), the HRP biocathode was functional in the presence of glucose with no essential loss in I-V characteristics. The biocathode performance and possibilities for its optimization were studied and compared with the hitherto existing biocathodes and biofuel cell designs.