were studied by the total electron yield method. Peaks were observed at 59.9, 60.3 and 61.4 eV in the XANES spectra of Li 3 PO 4 , Li 2 SO 4 ·H 2 O and LiNO 3 , respectively. The peak of the each sample was assigned as the core exciton. In the XANES spectra of Li 2 O, Li 2 S, Li metal, LiOH·H 2 O and Li 2 CO 3 , there were shoulder structures at the same energy. To clarify the origin of each peak, the XANES spectra were examined with the discrete variational (DV)-Xa molecular orbital method. Comparing the measured spectra with the calculated wavefunction, the shoulder structures at 61.8 eV (Li 2 O) and 60.4 eV (Li 2 S) in the XANES spectra were assigned as the core excitons, which appeared as remarkable exciton peaks in the lithium halide spectra. The spectrum of each lithium compound could be classified according to the shape of the core exciton peak, namely either a sharp or a shoulder structure. The strength of the ionic bond determined which of these shapes a core exciton peak assumed.

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We measured the Li K-edge spectra of lithium halides by means of total electron yield method (TEY), using the soft x-ray Beam Line 2 (BL2) of the compact synchrotron radiation facility at Ritsmeikan University in Japan. In lithium halides, the spectra have a sharp peak at about 60eV and a broad peak at the higher energy side. Various peak structures that appear in the absorption spectra are assigned to the corresponding Li-1s to valence band free orbitals transitions, which have been calculated by the Discrete Variational (DV)-Xalpha molecular orbital calculation method.

The mechanical durability of sulfonated poly (phenylene) (SPP) membrane, used for polymer electrolyte fuel cells (PEFCs), is evaluated by the United States Department of Energy (USDOE) stress protocol involving wet-dry cycling, and the degradation is analyzed specifically by comparing with sulfonated poly(arylene ether ketone) (SPK) membrane. Initially, the SPP membrane exhibits 2-fold higher stiffness and 50% lower dimensional change ratio than the SPK membrane. In durability cycling, the SPP membrane lasts more than 20,000 wet-dry cycles without mechanical failure, which is more than 5-fold better durability than that for the SPK membrane. Higher mechanical strength and lower dimensional change can reduce both irreversible membrane deformation and mechanical stress attributed to the membrane swelling and shrinking. In post-test analyses, the SPP membrane is found to rupture in the peripheral region of the membrane electrode assemblies. The SPP membrane maintains only 10% of the elongation at break in the peripheral region but 50% in the electrode region, compared with the pristine condition. It is most likely that the membrane deteriorates in the peripheral region due to stress concentration by cell compression and membrane deformation during wet-dry cycling. For the commercial use of the polymer electrolyte fuel cells (PEFCs), hydrocarbon (HC) membranes are expected to be nextgeneration membrane alternatives to conventional perfluorosulfonic acid (PFSA) membranes (e.g., Nafion), due to their low manufacturing cost, low through-membrane gas permeability, flexibility in molecular design and environmental compatibility.1,2 However, it is necessary to improve proton conductivity, chemical durability and mechanical durability to the same levels as those for the PFSA membranes under practical fuel cell operating conditions. To meet these targets, HC membranes have been developed intensively during the past decade. For example, polymer composition and morphology have been modified to maintain high proton conductivity, even under low humidified conditions. Acid-functionalized aromatic polymers such as poly (arylene ether) The oxidative stability of the HC membrane is also a key issue for the chemical durability. Oxidative dissolution of the membrane results in gas leakage through the membrane, and the degradation products of the membrane specifically adsorb on the Pt surface and block the oxygen reduction reaction, resulting in voltage losses. 17The oxidative stability of the HC membrane is enhanced by increasing the numbers of hydrophobic groups, decreasing water absorbing capacity 18 and introducing electron-withdrawing sulfone or ketone groups, as well as sulfonic acid groups, into the hydrophilic regions. 19Based on these backgrounds, we proposed an HC membrane that was composed of a sulfonated benzophenone poly(arylene ether ketone) (SPK) semiblock copolymer (Fig. 1a). 20,21 This membrane exhibited higher oxidative stability than those of conventional HC membranes, due to the introduction of chemically stable co...

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