Air and fuel starvation of phosphoric acid fuel cells: A study using a single cell with multi-reference electrodes

The changes in the anode and cathode potentials in the horizontal plane of a phosphoric acid fuel cell (PAFC) under starving conditions for either air or fuel were studied using a single cell furnished with twenty-four reference electrodes which were located around the anode or the cathode. When air starvation occurred, both the anode and cathode potentials became nearly 0 V against RHE, and hydrogen generation began to occur on the cathode side. Fuel starvation occurred when fuel utilization became more than 95%, and the cathode potential in the fuel outlet area shifted significantly toward the positive and, simultaneously, CO and CO₂ were detected in the air exhaust gas, indicating the occurrence of carbon corrosion of the cathode components. By further increasing the fuel utilization, the cell voltage changed to negative and the anode potential in the fuel outlet area became the highest. At that time, significant amounts of CO and CO₂ were detected in the fuel exhaust gas, indicating the occurrence of carbon corrosion of the anode components. Immediately after the termination of fuel starvation, the cathode potential in the fuel outlet area shifted quickly and remarkably toward the positive, and exceeded 1 V against RHE in a few seconds.