Polarization Study of a Fuel Cell with Four Reference Electrodes

Abstract

The changes in the anode and cathode potentials of a phosphoric acid fuel cell under various conditions were studied using a single cell equipped with four reversible hydrogen electrodes located near the inlets and outlets. When pure hydrogen gas was used as a fuel, the polarizations under load were homogeneous in the plane of the cell. However, when the reformate gas was used, inhomogeneity in the plane arose under load. The cathode and anode potentials shifted in the positive direction at the fuel outlet area. The potential shifts increased with an increase of fuel utilization or due to CO poisoning. The voltage loss due to CO poisoning ( CO loss) caused an increase not only of the anode polarization but also of the cathode polarization in the fuel inlet area. The increase of cathode polarization at the fuel inlet area was due to current convergence into the fuel inlet area. The potential shifts at the fuel outlet can be attributed to the acidity change of electrolyte there. The local acidity change of electrolyte can arise from a local starvation of hydrogen and hence of protons.

Carbon support oxidation in PEM fuel cell cathodes

“…the onset of reaction (5) is shifted from 0.9 V at pure carbon electrodes to that decidedly lower potential. Platinum catalyses the carbon oxidation reaction as reported in the literature [18] and significantly reduces overvoltage for reaction (5). This leads to an increase in corrosion rates compared to that of pure carbon electrodes (Fig.…”

“…The second state of irregular high-electrode potentials is characterized by partial fuel starvation of the active anode area of an individual cell in the stack. This condition may be caused either by local undersupply of hydrogen [5,6] or a hydrogen-air front passing over the active area during start up and shut down of the fuel cell [6,7]. Because oxygen-permeation from the cathode over the membrane into the anode compartment cannot be prevented, oxygen is present in the hydrogen deficient areas on the anode.…”

Analysis of oxygen sources and reaction pathways of carbon support corrosion at the cathode in PEMFC using oxygen-18 DEMS

“…CSC is a key contributor to cathode catalyst degradation in PEMFC [6][7][8][9][10][11][12][13][14]. It accelerates catalyst sintering by shortening the distance between Pt nanoparticles as the support corrodes away [6][7][8][9][10][11][12], and decreases anchor sites on the support for Pt nanoparticles so as to facilitate their movement [13].…”

“…It accelerates catalyst sintering by shortening the distance between Pt nanoparticles as the support corrodes away [6][7][8][9][10][11][12], and decreases anchor sites on the support for Pt nanoparticles so as to facilitate their movement [13]. It also causes changes of pore morphology and surface characteristics in the catalyst layer, away from the optimized conditions for mass transfer, resulting in performance decrease [14].…”

Catalyst Layer Degradation, Diagnosis and Failure Mitigation

“…It is also observed that the anode potential increases with fuel utilization. At 95% fuel utilization the anode potential rises to between about 0.4 V and 0.5 V, and the cathode potential at the fuel outlet approaches the open circuit voltage [63]. High anode potential could also occur when oxygen crosses over to the anode side and at the same time the fuel supply is insufficient.…”