In this paper, we have established that poly(neutral red), PNR, functions as an electrocatalyst for the reduction and oxidation of NAD(+)/NADH in a rechargeable biobattery environment. The reversibility of this catalyst was possible only with the addition of Zn2+ for complexation to the redox polymer. The zinc ion complexation with the polymer facilitates electron and proton transfer to/from the substrate and the NAD(+)/NADH coenzyme without forming covalent bonds between the nicotinamide and the substrate surface. This research presents use of this reversible catalyst in a rechargeable biobattery. The rechargeable battery includes a Prussian blue cathode and a bioanode including NAD(+)-dependent alcohol dehydrogenase and zinc complexed PNR. This bioanode was coupled to the cathode with Nafion (R) 212 acting as the ion exchange membrane separator between the two compartments. The biobattery has an open circuit potential of 0.545(+/- 0.009)V when first assembled and 0.053(+/- 0.005) V when fully discharged. However, when fully charged, the biobattery has an open circuit potential of 1.263(+/- 0.051) V, a maximum power density of 16.3(+/- 4.03) mu Wcm(-3) and a maximum current density of 221(+/- 13.2) mu A cm(-3). The efficiency and stability of the biobattery were studied by cycling continuously at a discharging rate of 1 C and the results obtained showed reasonable stability over 50 cycles. (C) 2010 Elsevier Ltd. All rights reserved.