SPE Electrodes

Platinum chemically deposited on a Nafion membrane was used as a platinum SPE (Solid Polymer Electrolyte) electrode. The electrochemical measurements were performed using the half cell shown in Fig. 2-2. The cell body is made from Teflon (PTFE). The cell is divided into two compartments one for backside gas supply one for the electrolyte. SPE electrodes are placed between them with the deposited side facing the gas compartment. A gold foil with a hole was placed behind the SPE electrode... 

The cel used for formation of SPE electrodes is shown in Fig. 2-12. To make a tight contact between the membrane and platiniun layer, small amount of platinum partides were deposited as nudei. Then a thick layer of platinum was deposited. This is a new way to fabricate a SPE electrode. 

Liu and Fedkiw proposed another SPE electrode formation method, in which cationic salt of platinum instead of chloroplatinic acid, which is used by Takenaka and Torikai, was first impregnated in Nafion and was later reduced chemically. a They showed that product distribution varies depending on the way of the deposition and oxidation conditions. ... 

The cell for SPE electrode studies was the same one shown in the earlier chapter. To supply methanol om the gas phase and to control the temperature, the system shown Fig. 3-3 was used. The electrochemical cell was placed in a convection furnace whose temperature was precisely controlled. The reference electrode was placed outside of the furnace and the connecting electrolyte tube was cooled with water jacket to prevent the tube from being blocked by the vapor. 

Fig. 3-. i Schematic diagram of the system for electrochemical experiments for SPE electrode... 

From this result, the lai er methanol oxidation current of the Nafion SPE electrode seems to be attributed to this resistance against the contamination rather than the intrinsic activity for the methanol oxidation. 

Sammclls et al. prepared a Cu coated SPE electrode using a CEM Nafion 11 . They reduced CO2 to C2H4 and C l 1 with the current density of 10 to 30 mA cnf with the terminal voltage 1.5 to 3.5 V. The faradaic efficiency for CO2 reduction remained less than 10%. 

The use of a perfluorinated ionomer as the SPE electrode binder results in better adhesive bonding with the membrane by virtue of the fact that the binder and the membrane are of identical composition. In addition, the solvent in the electrode paste promotes "solvent welding" by softening the membrane during the application process. 

The gain in a voltage drop when applying the SPE electrodes naturally, grow with a dilution extent of the used acid. This gain, however, is concerned not only with a voltage drop in the electrolyte, but also with the fact, that overvoltage of both cathode and anode processes is decreased on suoh electrodes with rather developed siu face. Distribution of current in SPE is also improved, since electric field between the electrodes becomes more uniform. 

The polarization resistance of Pt-Nafion electrode. Electrochim Acta 29 1721-1724 Kita H, Nakajima H (1986) Metal electrodes bonded on solid polymer electrolyte membranes (SPE)-III. CO oxidation at Au-SPE electrodes. Electrochim Acta 31 193-200... 

Wang, J., Nakajima, H., and Kita, H. (1990) Metal electrodes bonded on solid polymer electrolyte membrane (SPE) VI. Methanol oxidation on molybdenum modified Pt-SPE electrode. Electrochimica Acta,... 

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