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A normalPt‐H2WO4 based electrocatalyst has been fabricated by an inexpensive chemical route for use as an oxygen cathode in 99% phosphoric acid at 180°C. The effect of %Pt (w/w) and %H2WO4 (w/w) on the normalPt‐H2WO4 electrode performance was studied. The electrocatalytic properties for the oxygen reduction reaction, e.g., exchange current density, mass activity, and specific activity of a 2% normalPt‐H2WO4 based electrode was several times higher than those of 10% Pt. The performance of the 2% normalPt‐1%H2WO4 was not due to an increase of its electrochemically active surface area. This may be due to electronic interaction and synergetic effects between electrocatalyst and support and its chemical composition.

A 2% Pt-1% H2W04-based electrocatalyst has been fabricated by an inexpensive chemical route for use as an oxygen cathode in 99% phosphoric acid at 180°C. The effect of the platinum particle size on the electrode performance for the oxygen reduction reaction (ORR) was studied. The electrocatalytic properties for the ORR, e.g., exchange current density, mass activity, and specific activity of a 2% Pt-1% H,W04-based electrode fabricated from 5% Pt, were found to be several times higher than those of 10% Pt-based electrocatalysts. It was shown that the performance of this electrode is not related to an increase in its electrochemically active surface area, but to its chemical composition. Based on the concept of synergistic process of the ORE on materials we have previously emphasized, it is shown that a 2% Pt-1% H,W04-

According to the authors' latest experimental work s , the usage efficiency of sintered CCM sample (Ca09La0 ~MnO2.97, void = 57%, core = 0) was found to be 46% (or 100%) under the assumption that all Mn 4+ was reduced to Mn ~+ (or Mn 3+) after discharge. On the other hand, the calculated effi-ciency was less than 25% as shown in Fig. 8. This wide difference between the experimental result and the calculated one is attributed to the heterogeneous consumption of CCM in the real system, which means that CCM away from the collecting electrode reacts more preferentially than that near the electrode under the experimental conditions.