Advanced Materials Research Vols. 512-515

Abstract: A high efficiency simultaneous cellulose degradation and hydrogen production strain X9 was obtained from the screening of the 125 strains of fermentative hydrogen production bacteria which were isolated from a continuous stirred-tank hydrogen production bioreactor (CSTR) with LM-1 and microcrystalline cellulose (MCC) medium and improved Hungered technique in this study. X9 was confirmed a new category by analyzing the results of biochemical and physiological test, shape character, 16S rDNA sequencing and phylogenetic, and then analysis characteristics of growth, culture parameters, the effects of components of medium on growth and ability of hydrogen production, the optimum technological parameters have been determined from orthogonal experiment and single factor test. Finally, X9 achieved maximum specific hydrogen yield of 4.9mmol/g with MCC under the optimal conditions.

Abstract: The sharp rise in the development of vehicle industry in China not only promotes both the national economy development and the people living quality, but also aggravates both the national energy security and the environmental issues. Adopting alternative fuels instead of petroleum is commonly regarded as the utmost promising solution, however, which alternative fuel(s) is more suitable for China is still in the argument. The present paper compared the characteristics and performance of hydrogen gas and fossil-based fuels, and pointed that hydrogen gas is more suitable for China than fossil-based fuels.

Abstract: The study investigated bioelectricity generation from three types of wastewaters including artificial (AW), buffered brewery (BW) and buffered canteen (CW), in double chamber microbial fuel cells (MFCs). The biochemical oxygen demand (BOD) concentrations of influent were varied in the range of 125 - 1000 mg L-1. Influent pH and operation temperature were fixed at 7 and 30oC. 0.35 mL min^-1 wastewater was fed into a half-cell anodic chamber, while 5 mL min-1 oxygen-saturated distilled water was fed into a half-cell cathodic chamber. The circuit resistance was fixed at 10 ohms. The results showed that maximum current output obtained from AW, BW and CW with the initial BOD concentration of 1000 mg L^-1 were 0.92, 0.78 and 0.70 mA, respectively. The currents were directly proportional to the BOD concentrations in the influent for all wastewaters. The maximum BOD removal of AW, BW and CW was 90, 65 and 75%, respectively.

Abstract: Fungal biofuel cell comprising of liquid culture suspension of Gloeophyllum and Rhizopus fungal strains is studied. Gloeophyllum liquid culture forms the anolyte of the microbial fuel cell (MFC) while Rhizopus liquid culture which forms the catholyte. Bioenergy is harvested from biocatalytic redox reactions of glucose/oxygen as a result of metabolic activities of respective fungi. Pyranose-2-oxidase of Gloeophyllum catalyzes oxidation of glucose, whereas laccase produced by Rhizopus catalyzes oxygen reduction. Upon incubation period of 8 days, the Gloeophyllum-Rhizopus MFC is capable to deliver 5 mW of power output continuously for 21 days under uncontrolled, open ambient surroundings. MFC with such performance characteristics is sufficed to power remote sensing devices.

Abstract: A dark hydrogen fermentation process of food waste by Clostridium butyricum TISTR 1032 was examined under the condition of initial pH 6, 37oC and varied condition with oxygen scavenger in 5 L semi-batch reactors. Results showed that oxygen scavenger significantly elevated the maximum rate of hydrogen production (R_m) (203.5 mL h^-1) compared to that without oxygen scavenger (30.6 mL h^-1). However, it did not improve the maximum cumulative hydrogen production (Hmax). Carbon mass balance was used to explore the direction of fermentative process including toidentify type of fermentative process. Butyric acid fermentation was recognized as the fermentation type of this study under both conditions. Drop of pH and accumulation of total undissociated acid considerably reduced the hydrogen production.

Abstract: _{Subscript text}An anode material of Ce sub>1-xFe_xO sub>2-δ (x=0.1, 0.2) for the oxidation of dry methane has been investigated. Ce sub>1-xFe_xO_2-δ is synthesized by the citrate method. The electrochemical behavior of anode is analyzed by electrochemical i_{Subscript text}mpedance spectroscopy. Ce_1-xFe_xO _2-δ (x=0.1, 0.2) has shown the properties of electrochemical oxidation of methane at these temperatures (550~700°C) and the polarization resistance decreases with increasing Fe content. The Ce0.9Fe0.1O2-δ showed little degradation in long-term operation while the Ce_0.8Fe _0.2 O sub>2-δ showed degradation.

Abstract: In this study, four strains of Chlorella genus and four strains of Tetraselmis genus were investigated to research their in vitro hydrogenase activities and hydrogen productions. C.sp.-3 showed the second highest in vitro hydrogenase activity with 297.48 nmol H₂/(μg Chla h) and the highest volume of H₂ production with 10.246 μl/L among all the strains. Although T. sp.-3 exhibited a much low H₂ production of 0.298 μl/L, its in vitro hydrogenase activity was the highest with 315.92 nmol H₂/(μg Chla h). During the continuous culture of five weeks, the hydrogen production of C. sp.-3 reached the peak at 3rd weeks with 12.46 μl H₂ per liter culture, and decreased subsequently. In contrast, that of T. sp.-3 increased slowly and gradually with the culturing time, and was much lower than that of C. sp.-3 at each culture phases. These results showed that hydrogen production was a complex process that was determined not only by strain types but also by other factors, and that both C.sp.-3 and T. sp.-3 in the 8 strains were the most promising ones in hydrogen production and were worthy of further research.

Abstract: The isosteric heat of adsorption was used to study the interaction between hydrogen molecules and the Multi-Walled Carbon Nanotubes (MWCNTs). Characterizations of the MWCNTs sample were carried out based on the N2 adsorption isotherm at 77 K and the images from TEM and HRTEM. Step by step method was used to volumetrically measure hydrogen adsorption isotherms at equilibrium temperature-pressures from 123-310 K and 0-12.3 MPa. Isosteric heats of adsorption at seven excess adsorption amounts and that at zero surface loading were respectively determined by the slopes of the adsorption isosteres and the plot of the temperature dependence of the Henry’s constants. Results show that the limit of the isosteric heat of adsorption at zero surface loading is about and the mean under the experimental condition is about . The values are in the same grade as those of hydrogen on the activated coconut charcoal but smaller than those of hydrogen on the graphitized carbon black P33, the activated carbon AX-21 and the Single-Walled Carbon Nanotubes (SWCNTs). Conclusions are drawn that relatively lower adsorption amounts and the isosteric heat of hydrogen adsorption on the MWCNTs could be ascribed to the small specific surface area and the large mesopores.

Abstract: The production of hydrogen with the exhaust energy of an internal combustion engine was investigated in this paper. Steam reforming of methanol is an efficient way to generate hydrogen at relatively low temperature. The reactants of this process are methanol and water, and the hydrogen yield may reach as high as 75% theoretically. However, this is an endothermic reaction, and additional energy has to be provided to this process. If copper oxides and zinc oxides are used as catalyst, the reaction may proceed at the temperature of 270°C. A heat exchanger was designed in this study to use the hot exhaust of a diesel engine to convert methanol to hydrogen. This system is composed of a reformer, a heating chamber, a by-pass valve, and a control valve. Methanol was mixed with pure water at the ratio of 1:1 to form methanol solution. The flow rate of the methanol solution was adjusted according to the engine speed and load such that the thermal energy of engine exhaust may be fully utilized. The reformer is made of copper tubes and compact alumina fins. Pills of catalyst were filled inside copper tubes. Hot exhaust gas flowed through fins and transferred heat to methanol solution. Methanol solution at room temperature was fed into the reformer at a specified rate. It was heated and vaporized inside the copper tube, and then converted to the final products. It was found that in our system the molar fraction of H2 in the reformed gas was 72.6%, while that of CO2 was 23.5%. The exhaust temperature of a diesel engine varies in the range of 250°C~450°C, depending on the load of engine. It is quite sufficient to generate hydrogen with engine exhaust in a methanol reformer. In our system, the hydrogen rate of 17.3 L/min can be obtained in the exhaust pipe of a diesel engine with the displacement volume of 6000c.c. It was found that 49.5% of thermal energy can be recovered, and 92.6% of the recovered energy can be converted. In total, 36.7% of the waste energy can be recovered and stored in the reformed fuel.

Abstract: We investigate glucose oxidase-laccase EFC employing simplified system design – freely suspended enzymes in a membraneless, single chamber cell. The highly specific enzyme reaction mechanisms permit such system design. The EFC comprises nickel mesh as the oxidative current collector and a carbon-based air electrode as the reductive current collector, enclosed in acrylic casing of 3 ml volumetric capacity. The air electrode also serves as the ambient oxygen diffusion site to continuously feed oxygen into the system. The anolyte consists of glucose oxidase enzyme (10 U), glucose substrate (200 mM) and FAD co-enzyme (3.8 mM), while the catholyte consists of laccase enzyme (10 U) and syringaldazine substrate (216 µM). The cell employing citrate buffer electrolyte of pH 5 exhibits the best characteristics i.e. an open circuit voltage (OCV) around 960 mV and able to sustain continuous discharge current of 30µA for about 31.75 hours. The cell possesses volumetric power density of 286 W/cm³ which is considered comparable to biocatalytic energy systems employing much more complicated design.