Preparation and Electrode Materials

the most commonly used electrode is the PTFE-bonded GDE, and various procedures have been described for their production. The preparation procedure for rolled electrodes will be described in detail to illustrate the composition of PTFE-bonded gas electrodes. Rolled electrodes are composites of a metal catalyst and PTFE supported by a metal grid on the back side of the electrode. The metal grid is responsible for high electrical conductivity and also for mechanical support and stability. 

PTFE is used as an organic binder to link the catalyst particles and to produce a multifunctional electrode. For G D Es, hydrophobic and hydrophilic pore systems are required. For porous catalysts, for example, the Raney nickel catalyst, hydrophilic materials allow the penetration of the electrolyte into the electrode and the transport of the ions between the reaction zones the hydrophobic pore system - outside the catalyst - is required for the transport of gases to the reaction zones. In addition, to provide mechanical stability, the PTFE in the electrodes forms a hydrophobic pore network. 

The structure can be compared to a composite of particles that are linked by PTFE fibers that cover each particle. PTFE yields a hydrophobic pore network that is not flooded by the alkaline electrolyte, and the electrode can be supplied with the fuel gas from the back side of the electrode. 

Different catalysts are used for AFCs. For the hydrogen oxidation reaction, carbon-supported platinum and platinum-palladium catalysts (e.g., noble metal catalysts) are suitable. However, one of the advantages of the AFC compared with acid electrolyte fuel cells, including the phosphoric acid fuel cell (PAFC) and the 

is that non-noble metals are also stable in an alkaline environment. The greatest advantages of AFCs are that non-noble catalysts can be used and that an expensive and hfetime-reducing ion-conducting membrane can be avoided, thus drastically reducing the material cost. 

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