Effect of compressive force on the performance of a proton exchange membrane fuel cell

The effect of the compressive force on the performance of a proton exchange membrane fuel cell has been examined experimentally. The performance has been evaluated on two polarization regions of the cell: ohmic and mass transport. Cell voltage and current density as a function of pressure were measured under constant load and various inlet air humidity conditions. The pressure distribution on the surface of the gas diffusion layer was measured using a pressure detection film and the results show that increasing the pressure improves the performance of the cell. The improvement of the cell voltage in the ohmic region was found to be greater than that in the mass transport region, whereas for the cell current density, the mass transport region exhibited higher change. The increase in the cell specific power in the ohmic and mass transport regions, as pressure increases from 0 to 2MNm-2, is estimated to be 9 and 18mWcm−2, respectively. However, the fuel cell performance in these two regions declined dramatically when excessive pressure (≥5 MNm−2) was applied. The mass transport region proved to be more susceptible to this sharp decline under excessive pressure than the ohmic region

Preparation of bis(¿6-2-R-benzo[b]thiophene)-chromium and -molybdenum (R = H, Me, SiMe3) sandwich complexes via metal vapour synthesis. Crystal structure of [Cr(¿6-2-Me C8H5S)2]

Co-condensation of chromium atoms with benzo[b]thiophene, 2-methylbenzo[b]thiophene or 2-trimethylsilylbenzo[b]thiophene at 77 K yields the sandwich complexes [Cr(¿6-C8H6S)2] (1), [Cr(¿6-2-MeC8H5S)2] (2) and [Cr(¿6-2-SiMe3C8H5S)2] (3). The molybdenum complex [Mo(¿6-2-MeC8H5S)2] (4) was prepared analogously. Complexes 1, 2 and 4 exist as a mixture of diastereoisomers as indicated by 1H and 13C NMR spectroscopy, with mesomeric and racemic forms present in the ratios 1:1 for 1 and 1:2 for 2 and 4. The mesomeric form of complex 2 was also studied by single-crystal X-ray diffraction which confirmed ¿6-ligation of the arene function of both 2-methylbenzo[b]thiophene rings