Stack Assembling experience

Most of the evaluations on a stack are similar to those on a single cell. The V-I polarization curve is used to eshmate the stack s performance from lower to middle and to higher current densities. Parameters such as the humidi-ficahon temperature, temperatures of the coolant at the stack inlet and the outlet, the coolant flow rate, the reactant stoichiometric ratio, and the RH should be optimized through experiments. The compression force on the stack assembly should seal the stack but not cause damage to the GDM. 

Fig. 1.41. Micropositioning assembly in the MIM tunneling experiment. In an aluminum block (1), two gold electrode.s (2) are contained. The right electrode is attached to a pair of membranes (3), and actuated by a stack of piezoelectric plates (4). The left electrode is actuated by a differential screw (5) for coarse positioning. The entire assembly is enclosed in a thermostat and then a vacuum chamber. (After Teague, 1978.)...

Fuel cell stacks are assembled by Ballard and tested in application situations such as vehicles and stationary power. Operating experience... 

Another question is which one, the bis coordination of O2 to two CoP centers or the electronic effects induced by the peripherally coordinated Ru(III)Ru(III) Ru(II), would be responsible for the cobalt porphyrin activation in the multielectron-transfer process. In fact, considering that the Co(4-TCPyP) films are formed by stacks of supermolecules, it is not possible a priori to rule out the first hypothesis. This problem was solved by repeating the experiments using the electrostatic assembled Co(4-TCPyP)/ZnTPPS films in which the bis coordination of dioxygen to two cobalt porphyrin centers is not possible (176). The catalytic behavior is reproduced in the ion pair film, confirming that the activation is mainly due to electronic effects induced by the peripheral ruthenium clusters, in synergistic association with their normal role as intramolecular multielectron source. 

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