Fuel cell voltage end efficiency

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Thermo
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I know theoretically fuel cell efficiency decreases as temperature increases. But in practice it is vice versa. What is the reason of that? I couldn't find enough sources. Any kind of help is much appreciated.
 
Thermo said:
I know theoretically fuel cell efficiency decreases as temperature increases.
Source?
 
Even though a fuel cell is more efficient at lower temperatures as shown in Table 3.1, the voltage losses are much less in higher temperature fuel cells. Therefore, it is more advantageous to run a fuel cell at a higher temperature yet lower efficiency to produce higher operating voltages.

Table 3.1 listing Gibbs free energy, maximum EMF and efficiency limit of water at temperatures from 25 to 1000 °C, for liquid and gas states.

Source: Chris Rayment Scott Sherwin Department of Aerospace and Mechanical Engineering University of Notre Dame Notre Dame, IN 46556, U.S.A. May 2, 2003
Enough?...