Electrolyzer with proton-conducting membranes

In addition to the oxygen separation membranes, the proton conducting membranes can also be applied to reduce NO emission by combining heterogeneous catalysis and solid state electrochemistry. The solid electrolytes in MRs serve to electrochemically control chemisorptive bonds and enhance catalytic activity. Figure 8.10 shows the schematic diagram of a steam electrolysis cell constructed with a proton conductor for reducing NO. Steam is electrolyzed at the anode. It shows the produced H+ is electrochemically pumped to the cathode and reacts with NO to produce Nj and HjO ... 

MEAs tested so far, had established that use of Ft/C catalysts on the anode reduced the performance of the SPE electrolyzer. In addition flow rate had been optimized, trends with temperature were observed, the effect of using alternative proton conducting membrane on SPE performance, and a suitable carbon-based GDL had been demonstrated. The use of a titanium fiber based GDL was identified as an option to optimize SPE performance via judicious selection of material components that make up the system. MEA 42 was assembled using a proton conducting membrane from GEEC (GEEC 117), commercial iridium oxide catalyst on the anode and titanium fibers GDL on both anode and cathode side. In contrast, MEA 51 was made with a homemade iridium oxide catalyst on the anode, Bekinit GDL on the anode and... 

Bipolar electrolysis systems are characterized by the type of electrolyte. The proton exchange membrane (PEM) system, developed by the General Electric Compare (GE), uses as the electrolyte a thin membrane of sulfonated fiuorocaibon (Nation ) that conducts electricity when saturated with water. Electrodes are formed by depositing a thin platinum film on opposite sides of the merrtbrane to form a bipolar cell. An electrolyzer is made by stacking 50-200 cells in series, with srritably formed separators to direct the exhaust gases into charmels at the sides. Since the membrane is the electrolyte, only pine water needs to be supphed to the cell. When the cell oper-... 

PEMs are also used as electrolytes in PEMECs whose electrolyzer has similar configuration to PEMFC. However, the hydration state of the membrane differs between fuel cell operation and electrolysis operation. During PEMFC operation, the membrane is humidified and equilibrated with water vapor, whereas during electrolysis operation, Nafion membrane is exposed to liquid phase of water and fully hydrated during water electrolysis. This leads to the big differences related to water uptake, swelling ratio, and proton conductivity between PEM water electrolysis and PEMFC. 

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