FUEL CELLS: APPLIED RESEARCH FUEL CELL MATERIALS AND ELECTROCATALYSIS

摘要

One of the main reasons for the loss in performance with time in fuel cells is due to the sintering of the catalyst particles. The fast cycling method was used for the periodic regeneration of unsupported Teflon bonded platinum black electrodes. Experiments were conducted in 85％phosphoric acid at 150°C. The time variation of current density for oxygen reduction at a potential of 0.6 volts vs. the reversible hydrogen electrode was recorded. The surface areas were measured in situ at desired time intervals by the hydrogen adsorption technique. After 1000 hours, there was a decrease in current density and electrochemically active surface areas by about 40％. By cycling the potential of the electrode between 0 and 1.3 volts at the optimum sweep rate of 100 volts/sec, the initial activity and surface area could be restored. The rate of decay of current density with the rejuvenated electrode followed the same pattern as the fresh electrode. On the basis of the results obtained, the mechanism of regeneration by the fast cycling method appears to be by a charge injection on the agglomerated particles, which causes an electrostatic repulsion and hence a dispersion of the particles.