Effect of non-graphitized carbon electrodes on the electrochemical characteristics of a thermocell with a Br2/Br- redox couple

Electrodes made from a non-graphitized carbon (Maxsorb) sheet with a large specific surface area greatly improved the electrochemical characteristics of thermocells with a bromine/bromide-ion redox couple and a KBr aqueous electrolyte saturated with Br2. The Maxsorb electrodes provide a higher open-circuit voltage than graphite (Perma Foil) eletrodes and the maximum discharge current density is 2.4 mA/cm(2) until the voltage reaches 0 V. The Maxsorb electrodes generate 5.68 mV/degrees/C of thermoelectric power at a temperature difference greater than 40 degrees C, which is 2.5 times the power reported previously. The Maxsorb electrodes also improve the cathodic polarization in the presence of a gas-liquid-solid interface in Br-2-free electrolyte, while the graphite electrodes do not. Nevertherless, this improvement is insufficient in observe when the KBr electrolyte is saturated with Br-2. An experiment cell with Maxsorb electrodes maintains a stable voltage up to 2.0 mA/cm(2) for over 450 h, even though the cell configuration has still to be optimized. (C) 1998 Elsevier Science S.A.