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The cost reduction of hydrogen stations is a must in order to spread fuel cell vehicles. Generally, the PSA device in the hydrogen station occupies 30% of the construction cost. We have already proposed the cost reduction by replacing the PSA and CO shift converter with a membrane reactor to which CO2 selective facilitated transport membrane is built in 2011. Although the CO2 facilitated transport membrane achieved the CO2/H2 selectivity of 100 or more even if the operation temperature was 160°C, the durability was poor. Therefore, it is necessary to improve the heat resistance and the rate of reaction between carrier and CO2 furthermore so that it can be adopted for the membrane reactor. In order to improve the membrane performance at 160°C by keeping high water content of membrane, graphite rubbish was added to the membrane as it was expected to function as grain for water absorption. As a result, the CO2 selectivity of the membrane improved more than that of the previous membrane by 3 times.

The hydrogen station in Japan is only 17 points though Toyota began to sell FCV from 15th November, 2014. The main reasons for which the spread of HS is late are a high construction cost and the indefinitely of spread prospect of FCV. However, it became clear that FCV in Japan spreads surely because the order for FCV exceeded 1000 from release in one week. The remaining problem is to reduce the cost of construction of 300 million yen. Therefore, we proposed membrane reactor composed of the reformer and the CO2 facilitated transport membrane to reduce the construction cost. It is necessary to achieve heat resistance of 160°C so that it is adopted for the membrane reactor. Therefore, we aim to optimize the operating condition (humidity, partial pressure of CO2 and differential pressure) of NDP to obtain the indicator of the heat resistance improvement at first. As a result, it is clear that the optimum operating condition of NDP is 80% of relative humidity, 200kPaG of the differential pressure and 40kPaG of the CO2 partial pressure.

Hydrogen of hydrogen station for FCV is usually produced by the reforming reaction, followed by the water gas shift reaction. The reformed gas contains a large amount of CO2, and this decreases the power efficiency although it does not influence the PEFC performance. The CO2 removal technology from the reformed gas is an important factor to improve the FCV performance. We developed a membrane for selective CO2 separation containing carbonate salt as a CO2 carrier. The support material of the CO2 carrier for a selective CO2 separation membrane should have water solubility, mechanical strength and heat resistance. We evaluated three support materials, PVA, AQN and NDP. The PVA membrane was broken at high temperature region though it showed good CO2 permeance at low temperature region. The AQN membrane had low CO2 permeance in all temperature regions. Although the NDP membrane had CO2 permeance at high temperature region, it should be improved further to increase the CO2 permeance.

We developed a novel membrane reactor consisted of a CO shift catalyst and a membrane for selective CO2 separation. First, we successfully developed novel facilitated transport membranes with excellent performances exceeding our target values, i.e. CO2 permeance of 1x10-4 mol/(m2skPa) and CO2/H2 selectivity of 100 at 160 oC. The developed membrane maintained high performances for more than 400 hours. Second, we developed CO shift catalysts, which had high activity for the CO shift reaction at 160 oC. Among the catalysts developed in this study, precious metal-based catalysts had quite high activities. By combining the developed membrane and catalyst, a membrane reactor-type CO converter was fabricated. By using the CO converter, CO and CO2 concentrations in feed gas (14.8 and 7.4 %, respectively) were drastically reduced. Observed CO and CO2 concentrations at the feed-side exit of the CO converter were 5 ppm and 0.3 %, respectively.

The CuO/ZnO heterocontacts for carbon monoxide (CO) gas sensors were made using CuO ceramics with different histories, and their gas sensing characteristics were evaluated. The CuO/ZnO heterocontact made by the quenched CuO sintered compact showed enhanced CO and CO{sub 2} gas sensitivity, while that made by slowly cooled CuO showed no selective CO gas-sensing characteristics with no CO{sub 2} gas sensitivity. The quenched CuO ceramics were thermodynamically stable but the slowly cooled ones were not; therefore the adsorbed CO molecules on the quenched CuO are thought to be stable and have longer lifetimes. The specific reaction between the adsorbed CO on CuO and adsorbed oxygen on ZnO would be promoted by long lifetime adsorbed CO on CuO and that may be the origin of the enhanced CO gas sensitivity of the quenched-CuO/ZnO heterocontact. The concentrations of cation vacancies of the quenched CuO ceramics can be controlled by controlling the firing temperatures. However, when the CuO ceramics for the CuO/ZnO heterocontact were made by firing and quenching, the ability to be selective in CO gas sensing of the heterocontact was not easily controlled by the control of the defect concentrations of the CuO ceramics.

Sensitive and selective carbon monoxide (CO) gas detection by a simple device is one of the most important research topics for safe environmental control. The gas sensing characteristics of CuO/ZnO heterocontacts are investigated. CuO/ZnO heterocontact, with Na[sub 2]CO[sub 3] added, showed selective CO gas sensing properties, while pure CuO/ZnO heterocontact showed higher sensitivity to H[sub 2] than to CO. It is suggested that the presence of a second phase containing Na[sup +] in CuO ceramic is essential for selective CO gas sensing by a heterocontact.