A novel small size SOFC system for generating elevated voltages is proposed. The system consists of conventional single cells for single chamber SOFC and interconnections. The single cells are connected in series and placed in the direction of the gas flow. This fuel cell was named as single chamber SOFC with series connected cells (abbreviated to SSSC). In this study, we direct our attention to the analysis of series connected segments which play an important role in the SSSC system. A single cell of SOFC is divided into two segments and the effect of the partition on the power generation characteristics is discussed. The result of the calculation for the two segments cell revealed that the IV-IP characteristics of the cell are affected considerably by the lengths of the segments. The output power of the system is described as a function of the lengths. We obtained the greatest power when the lengths of the segments are equal. The maximum power of this two segments cell is obtained when hydrogen utilization is 68% in a calculation model. The maximum power is higher than that of the one segment cell by 2.0 mW. When the utilization increases to 85%, the difference of output power between one segment and the two segments cell increases to 5.2 mW. The origin of the difference is discussed in terms of the energy loss related to electrode overpotential. When either segment is considerably smaller than the other one in the two segments system, the output power of the system remarkably decreases. This is explained as an increase in the energy loss related to the IR drop in the smaller segment.
Composite membranes of zeolites and hydrated styrene butadiene rubber (HSBR) were investigated with a view to developing a new flexible electrolyte. The evaluated zeolites were multivalent-cation exchanged Y-type zeolites and various types of proton-substituted zeolites. The membranes were fabricated by casting method. The solid acidity of the zeolites was analyzed with the results of the ammonia TPD measurement. Two acid sites were observed in the measurement, that is, strongly and weakly adsorbed ammonia molecules were detected. In the multivalent-cation exchanged Y-type zeolite membranes, the conductivity increased with increasing the weak acid sites. The proton-substituted zeolite membranes were examined by the pyridine-IR method carried out in a reduced pressure. The membranes showed high conductivity when the Bronsted acid sites increased. A Ca2+-exchanged Y-type zeolite exhibited the highest ion conductivity of 6 × 10−5 S/cm. The measurement was made with a membrane containing 80 wt% of zeolite particles, at room temperature in the relative humidity of 100%.
The electrochemiluminescence (ECL) of luminol in a hydrogen peroxide solution was studied by an electrochemical impedance spectroscopy (EIS). Parallel Pt wire electrodes in a flow-type spiral cell were used for the measurements of ECL. A superoxide ion, O2−, was generated by electrooxidation of H2O2 on Pt, and a luminol was oxidized on Pt. The oxidized luminol fluoresces by a reaction with O2−. An ECL impedance L, which is the ratio of the luminescence amplitude to the current in the frequency domain, was measured. By comparing the theoretical equation with the experimental results of L, the rate constant for luminol luminescence was determined.
SO2 sensing properties of WO3 loaded with and without a metal have been investigated in the temperature range of 200-800°C. X-ray photoelectron spectroscopic studies and temperature programmed desoprtion spectra from SO2-preadsorbed WO3-based sensor materials were also conducted to clarify the adsorption states of SO2 and their electronic interactions, and then to discuss the SO2 sensing mechanism. The resistance of WO3 increased upon exposure to SO2 at temperatures lower than 500°C, due to the formation of SO2−ad at adsorption sites different from those for oxygen adsorbates. In contrast, the resistance of WO3 decreased in SO2 at temperatures higher than 550°C, due to the formation of SO42−ad by the reaction of a gaseous SO2 molecule and two O2−ad adions. The largest resistance change of WO3 induced by SO2, i.e. the highest sensitivity, was observed at 400°C. Among the metals tested, the addition of 1.0 wt% Ag resulted in the most significant enhancement in sensitivity at 450°C, while the resistance decreased in SO2 over the whole temperature range studied. In the case of 1.0 Ag/WO3 the resistance was determined mainly by the surface state of Ag. It was considered that the formation of SO42−ad was facilitated even at a temperature of 450°C by the reaction of gaseous SO2 and O2−ad on the Ag surface and that this caused the resistance decrease.
Barrier-type Al2O3 films were formed in aqueous solution containing sulfonate-based electrolytes by anodization of aluminum substrate without any particular surface treatment on it. The galvanostatic formation behavior of such “barrier-type” Al2O3 films was studied by measuring anode potential-time curves. As the electrolytes, the authors selected sodium salts of n-dodecylbenzenesulfonate (DBS), butylnaphthalenesulfonate (BNS), and n-dodecylsulfate(SDS), mono, di, and trivalent naphthalenesulfonates, sulfonate polymers, and inorganic sulfate. Among them, DBS and BNS showed high coulombic efficiency (η > 90%) to form a barrier-type Al2O3, which is comparable to that of ammonium adipate. The η was found to be high when HLB (Hydrophile-Lipophile Balance) of sulfonates is less than 40. Above 40(HLB > 40), the η became lower than 50%. It is concluded that higher hydrophobicity of the electrolyte leads to higher capability to form a barrier-type Al2O3.
The decomposition of low-concentrated ferrocyanide ion (≦51.28 × 10−4 mol dm−3) in acidic aqueous solution was investigated. While the concentration of ferrocyanide ion (CA) decreased with time, ferricyanide ion was formed: its concentration increased, and successively decreased through a maximal value. Therefore, we investigated first the decomposition behavior of sum of ferrocyanide and ferricyanide ions, i.e. hexacyanoferrate ions. The decomposition rate of hexacyanoferrate ions which followed first-order kinetics of CA increased with the rise in temperature and the drop in pH. That of ferrocyanide ion which also followed the first-order kinetics of CA increased with the rise in temperature but decreased with the drop in pH. The reaction mechanism of the decomposition of ferrocyanide ion and the formation of ferricyanide ion was discussed.