No abstract

Effective integration of electrochemical devices consisting of enzyme-based biobatteries together with high power double-layer type capacitors is discussed here. An ultimate goal is to overcome a typical drawback of enzymatic power sources (biofuel cells and biobatteries): although their energy is potentially high enough to fulfill the needs of small electronic devices, their power is often too low. It is demonstrated that properly selected capacitor can support operation of such a low power device simply by supplying appropriate power pulses with fast dynamic response that is required for many applications involving fluctuating loads. Our model integrated system is obtained by coupling a series of double-layer capacitors with wellbehaved zinc/oxygen biobattery. The biobattery utilizes a stable cathodic material composed of covalently phenylated single-walled carbon nanotubes and the oxygen reduction enzyme, laccase, together with the hopeite-covered zinc rod acting as the anode. The enzymatic power source was characterized by the maximum power density of 1.8 mW cm -2 , the open circuit voltage of 1.6 V. Nevertheless, under the 50 X loading, the voltage of biobattery (electrode surface areas of ca. 0.3 cm 2 ) drops to 0 V after 2 s. The practical performance (power stability) of a biobattery has significantly improved by its parallel connection to electrochemical capacitor. The importance of such capacitor's parameters as low resistance (not more than a few hundred of milliohms), proper capacitance, and leakage current (not higher than a few microamperes) is emphasized here. The potential utility of the optimized biobattery/supercapacitor system is discussed in terms of use as a source of power to operate a digital watch.

An important issue in solar cell technology is the storage of generated electrical energy for later use. In this respect supercapacitors, as compared to batteries and electrolysis cells, offer the advantage of long-term stability and relatively low energy loss in the charge-discharge cycle. In this study, ruthenium oxide has been selected as charge storage material for coupled (integrated) dye-sensitized solar cell and supercapacitor system hereinafter called as three electrode configuration. Organic D35 dye was used to sensitize TiO2 photoanode and a conducting polymer, (poly-(3-hexylthiophene-2,5-diyl) served as hole conductor. The photovoltaic part was separated from charge storage material by utilizing a thin layer of vapour evaporated silver. The specific capacitance, power density, coulombic and energy conversion efficiency of the hybrid cell was analyzed. The system was compared to that of our previous reports, i.e. two electrode configuration built of N719 dye modified TiO2 and poly (3,4-ethylenodioxythiophene)/carbon nanotubes composite as charge storage material.

No abstract

No abstract