Photovoltaic conversion using photosynthesis organ Grana from Spinach adsorbed nanocrystalline TiO2 layer onto ITO glass (OTE) electrode (Grana/TiO2 electrode) is developed. The shape of absorption spectrum of the Grana/TiO2 electrode is almost the same that of Grana solution. Absorption maxima of Grana/TiO2 electrode are observed at 450, 480 and 680 nm attributed to carotenoid and chlorophyll molecules. This result suggests that Grana are adsorbed onto nanocrystalline TiO2 layer onto OTE. The photocurrent responses of Grana/TiO2 electrodes are measured using acetonitrile with 0.1 mol dm−3 tetrabutylammonium hexafluorophospate as a redox electrolyte in the presence and absence of water with 100 mWcm−2 irradiation. Photocurrent of Grana/TiO2 electrode increases using the redox electrolyte containing water. Moreover, the photocurrent responses of Grana/TiO2 electrodes with monochromatic light (680 nm attributed to absorption band of photosystem II with oxygen evolved complex) irradiation are measured using acetonitrile with 0.1 mol dm−3 tetrabutylammonium hexafluorophospate as a redox electrolyte in the presence and absence of water. Photocurrent of Grana/TiO2 electrode using the redox electrolyte containing water only is observed, indicating that the evolved oxygen from water with photosystem II in Grana onto nanocrystalline TiO2 layer electrode by 680 nm irradiation is reduced to water with catalytic activity of platinum electrode.
To improve the segmented-in-series tubular SOFC performance operating at 1173 K, we studied cathode interlayer (CIL) and a structural modification of the cell stack using a performance simulation. As the result of changing CIL into (Ce0.8Sm0.2)O2 (SDC20) (type 2) from La0.7Sr0.3MnO3-YSZ (type 1), ohmic polarization (ηIR) and activation/concentration polarizations (ηA+ηC) of type 2 decreased 16% and 47% than those of type 1, respectively. Next, based on the simulation results of ηIR, a tubular SOFC (type 4) with structural modification in the length ratio of the effective generation part (EGP) and interconnector part (ICP) was fabricated by applying SDC20 to CIL. Ohmic polarization of type 4 decreased 52% than that of type 2, while ηA+ηC increased 63%. However, the generation performance of type 4 improved than that of type 2, since ηIR decreased more than the increase of ηA+ηC. In a pressurized test of type 4, an increase of pressure resulted in a decrease of the area specific resistance calculated from the inclination of I-V characteristics including EGP and ICP resistances. In a durability test of type 4 conducted for 7000 h in atmospheric pressure, a degradation rate of 0.73% 1000 h−1 was obtained.
Sintering is an important process in the preparation of solid electrolytes. Milling of the precursor powders generally increases their sinterability, and thus, an effective milling method is important to obtain dense electrolytes. In this study, we demonstrate that planetary bead milling provides nanosize precursor powders with markedly high sinterability. For BaZrO3, a proton-conducting oxide with low sinterability in its unmilled state, planetary bead milling with 0.2 mm beads enables a reduction in sintering temperature to 1400–1500°C, which is 300–400°C lower than usual. We also discuss the effect of bead milling on microstructure and conductivity.
Surface morphology of IrO2-Ta2O5 coatings produced by thermal decomposition was investigated by SEM with low accelerated incident electron beam. IrO2-Ta2O5 coatings consisting of crystalline IrO2 and amorphous Ta2O5 and of amorphous IrO2 and Ta2O5 were examined, and a significant difference in surface morphology between them was found. The coating comprising crystalline IrO2 showed a mud-cracked morphology with large segregated IrO2 particles, and the flat area was porous with nano holes and cracks in addition to non-uniformly dispersed IrO2 flakes of 20–60 nm. A smooth cracked surface with no segregated IrO2 was observed for the amorphous coating, and ordered nano IrO2 particles of 5–10 nm were further revealed.