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.
The photocurrents in zinc oxide and titanium dioxide electrodes sensitized by anionic xanthene dyes (Eosine Y, Phloxine B, Erythrosine, and Rose Bengal) and metal tetraphenylporphines were studied in aqueous solutions. The quantum efficiencies of the photocurrents sensitized by anionic xanthene dyes were unaffected by substitution of the dye with various halogen atoms, while those sensitized by the tetraphenylporphines were affected by changing the central metal. It is concluded from these results that the electron injection from the excited xanthene dyes to the semiconductor electrodes is a process so rapid (<<0.1 ns) that no internal quenching processes can compete with it, while that from the tetraphynelporphines is relatively slow competing with the internal deactivation processes. It is also concluded that the electron back transfer from the semiconductor conduction band to the oxdized dye decreases the sensitization efficiency.
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