Membranes, hydrocarbon polymer electrolyte

Despite perfluorinated polymer electrolytes (Nafion, Flemion, Aciplex) having been used extensively in PEMFCs, their poor thermal mechanical stability (low Tg), high methanol permeability, and extremely high production costs have led to limitations of their large-scale application. Therefore, a variety of hydrocarbon polymer electrolytes have been developed during the past decade, with the greatest emphasis placed on the costs, conductivity, and durability of these materials. At the same time, the poor mechanical stability and inadequate durability of the hydrocarbon polymer membranes were identified as the main barriers to their practical application. 

Hydrocarbon Membranes for Polymer Electrolyte Fuel Cells... 

Hydrocarbon Membranes for Polymer Electrolyte Fuel Cells, Fig, 1 BPSH/BPS block copolymer (A andB are the numbers of repeat unit of hydrophilic and hydrophobic blocks, respectively, n is the degree of polymerization)... 

Hydrocarbon Membranes for Polymer Electrolyte Fuel Cells, Fig. 3 Humidity dependence of the proton conductivity of SPESK block copolymer membrane (lEC = 1.62 meq/g) at 80 °C and 110 °C... 

While lots of PEMs have been developed, the sulfonated hydrocarbon polymer electrolyte (SHCPE) and perfluorocarbon sulfonated ionomer (PFSI) membranes are most widely investigated for LT-PEMFCs and DMFCs, and the PBI and its modified polymer membranes doped with H3PO4 are most widely applied to HT-PEMFCs. In the following sections, we discuss the morphologies and conducting mechanisms of the SHCPEs, PFSIs, and PBI doped with H3PO4 (PBI/H3PO4) membranes. 

Hydrocarbon Polymer Electrolytes for Fuel Cell Application (J. Qiao and T. Okada, 2008, Nova Science Publishers) focuses on composite membranes for direct methanol fuel cells. 

Electro-catalysts which have various metal contents have been applied to the polymer electrolyte membrane fuel cell(PEMFC). For the PEMFCs, Pt based noble metals have been widely used. In case the pure hydrogen is supplied as anode fuel, the platinum only electrocatalysts show the best activity in PEMFC. But the severe activity degradation can occur even by ppm level CO containing fuels, i.e. hydrocarbon reformates[l-3]. To enhance the resistivity to the CO poison of electro-catalysts, various kinds of alloy catalysts have been suggested. Among them, Pt-Ru alloy catalyst has been considered one of the best catalyst in the aspect of CO tolerance[l-3]. 

Under normal operation of an H2/O2 fuel cell, anodic oxidation of IT2 (or other hydrocarbons or alcoholic fuels)—that is, H2 —> 2H+ -1- 2e —produces protons that move through the polymer electrolyte membrane (PEM) to the cathode, where reduction of O2 (i.e., O2 -1- 2H+ -1- 2e —> H2O) produces water. The overall redox process is H2 -1-O2 —> H2O. The electronically insulating PEM forces electrons produced at the anode through an external electric circuit to the cathode to perform work in stationary power units, drive trains... 

S. Tsushima, S. Hirai, K. Kitamura, M. Yamashita, S. Takasel, MRI application for clarifying fuel cell performance with variation of polymer electrolyte membranes Comparison of water content of a hydrocarbon membrane and a perfluorinated membrane. Appl. Magn. Reson. 32, 233-241 (2007)... 

Rikukawa, M. Sanui, K. Proton conducting polymer electrolyte membranes based on hydrocarbon polymers. Prog. Polym. Sci. 2000,25 (10), 1463-1502. 

Several non-fluorinated alternative polymers have been proposed for DAFC, mainly based on sulfonated ionomers with an aromatic or aliphatic hydrocarbon skeleton [7], Kim and Pivovar [4] have reported the number of DMFC alternative membranes papers appearing in open hterature for years 1994—2004, showing that polyarylenes, polyvinyl alcohols, grafted and block polystyrenes copolymers, and polyimides were among the most studies polymer electrolytes. In view of the dramatic increase in the number of publications since 2005 (see Fig. 6.1), the trends have changed, as shown in Table 6.1, which sununaiized the publications in open literature for the period 2005-2012, as compared to the previous period. 

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