Membrane continued between ionic conductance

Guiver et al. of National Research Council, Canada developed comb-shaped poly(arylene ether) electrolytes containing 2-A sulfonic acid groups on aromatic side chains (d) [76]. Their membranes showed relatively high proton conductivity and well-developed and continuous ionic domains. However, trade-off relationship between water uptake and proton conductivity of their membranes was not better than that of Nafion. In order to pronounce the hydrophilic/hydropho-bic differences, another series of comb-shaped aromatic ionomers with highly fluorinated main chains and flexible poly(a-methyl styrene sulfonic acid) side chains were developed [77]. The membranes seemed to have better properties than their previous version, however, chemical instability of the side chains needed to be improved. 

The performances of the Nafion and the hydroxide-ion-conduction membrane cells were compared for two cathode solutions (1) D1 water (18 Mil cm) saturated with carbon dioxide by continuous bubbling of the pure gas at a pressure of 1 atm and (2) 1 M sodium bicarbonate solution. As shown in Figure 10.13, the cell voltages with the hydroxide-ion membrane were found to decrease substantially upon changing the electrolyte from C02-saturated D1 water to 1 M sodium bicarbonate. However, the performance of the Nalion-based cell did not alter significantly for the same change in the cathode solution. This phenomenon can be ascribed to differences in ionic contact at the electrode/manhrane interface, as hydroxide-ion membrane is cross-linked and could not be hot pressed to improve the ionic contact. Thus, the use of a liquid electrolyte could substantially improve the ionic contact between the catalyst layer and the hydroxide-ion-conduction manbrane. 

---