Alcohol Fuel Cell Passive Systems

Direct Alcohol Fuel Cell Passive Systems 

To the best of our knowledge, the only examples of passive DAFCs equipped with an anion-exchange membrane are those realized independently by Bianchini and Coutanceau.  

The membrane-electrode-assemblies (MEAs) described by Bianchini and coworkers comprise Fe-Co HypermecT K-14 cathodes by ACTA SpA, Tokuyama A-006 membrane and anodes coated with Pd/MWCNT, Pd-(Ni-Zn)/C or Pd-(Ni-Zn-P)/C electrocatalysts.  

The polarization and power density curves obtained with methanol, ethanol and glycerol in 2 M KOH solutions at room temperature (20-22 °C) are reported in Fig. 24 for DAFCs where the cathode is exposed to either air or 1 bar oxygen and the fuel solution (13-15 mL) is introduced into a static compartment facing the anode. 

From a perasal of Fig. 24, it is apparent that the Pd/MWCNT anode is particularly suitable for the oxidation of ethanol which shows the highest open circuit voltage (OCV, 0.74 V) and peak power density (18.4 mW cm at 0.2 V) out of the three fuels investigated. Notably, the performance trend in the passive DAFC is different from that observed in the half cell where glycerol provides the highest peak current density (Fig. 13). On the other hand, the lower performance of both the direct methanol fuel cell (DMFC) and the direct glycerol fuel cell (DGFC) as compared to the DEFC is in line with the chronopotentiometric experiments illustrated in Fig. 13. 

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Direct Alcohol Fuel Cell Passive Systems... 

There are different kinds of DAFC operation conditions depending of the way the fuel and the oxidant (oxygen/air) are fed into the cell. In complete active fuel cells the liquid fuel (neat alcohol or aqueous solution) is pumped and gas is compressed, using auxiliary pumps and blowers, in order to improve mass transport and reduce concentration polarization losses in the system. On the other hand, in complete passive DAFC the alcohol reaches the anode catalyst layer by natural convection and the cathode breathes oxygen directly from the air. A number of intermediate options have been also studied and tested. 

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