Abstract
One of the problems with the use of enzymes as catalysts in biofuel cells is to achieve good contact between the enzyme and the electrode surface. One solution to this problem is the use of various nanostructures such as carbon nanotubes, fullerenes, graphene derivatives, gold nanoparticles, as well as mediators for the construction of electrodes. Acetosyringone and promazine adsorbed on glassy carbon electrodes (GCEs) covered with multiwall carbon nanotubes (MWCNTs) and laccase were used as biocathodes. These mediators showed very efficient adsorption on modified glassy carbon electrodes covered with MWCNTs and enabled efficient and stable adsorption of laccase, which acts as the bioelectrocatalyst. Very good electrical contact between the electrode surface and the laccase enzymatic active sites made it possible to increase the catalytic current density of oxygen-reduction by about 82% compared to electrodes without mediators. Application of acetosyringone and promazine used in the construction of biocathode also improved the current and power of the biobattery ca. twice comparing to the system without mediators. The device output reached the power that equaled approximately 2 mW/cm2 at 0.8 V and open circuit potential (OCP) was 1.6 V. The systems elaborated proved also useful in oxygen sensing and allowed to determine lower oxygen concentrations in solution compared to the GCE modified with MWCNTs and laccase alone. The electrode showed also better stability in long-timescale measurements.
Highlights
More and more often, biofuel cells are used as alternative energy sources, supplying devices that require a small power consumption for their work [1,2,3,4,5,6]
This research field encounters serious problems, including obtained catalytic currents, the power of biofuel cells are too small, and the working time is not long enough to supply them in order to consider their possible applications [10]
Enzymes are used as catalysts
Summary
Biofuel cells are used as alternative energy sources, supplying devices that require a small power consumption for their work [1,2,3,4,5,6]. Biofuel cells consist of two electrodes that are able to convert chemical energy into electricity. They are a special kind of fuel cell, in which the sources of chemical energy are reduction and oxidation processes of naturally occurring renewable compounds present in the environment or in living organisms [10,11]. The catalysts of anodic processes are enzymes that catalyze oxidation reactions, e.g., lactate dehydrogenase, glucose dehydrogenase, alcohol dehydrogenase, glucose oxidase, fructose dehydrogenase, and the catalysts used most often to construct the cathode are laccase, bilirubin oxidase or cytochrome oxidase, which catalyze the reduction of oxygen to water [1,12,13,14,15]
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