Advanced Materials Research Vols. 512-515

Abstract: Energy crisis is paid more attention to its significance around the world. Hydrogen is considered the most potential alternate energy source due to the character of non-pollution and zero emissions. This paper researched the variation of hydrogen-producing rate, pH value and the proportion under five temperatures of 25°C, 30°C, 35°C, 40°C, 45°C through batch culture and the reasons of these appearance. And anaerobic hydrogen-producing bacteria’s isolation and enrichment culture was accomplished by Hungater’s anaerobic technique. The time of logarithmic phase was 24h, 16h, 12h, 20h and 28h and the stationary phase was 36h, 28h, 24h, 32h and 36h at 25°C, 30°C, 35°C, 40°C, 45°C. When the pH declined to 4.2-4.4, the hydrogen-production rate and the proportion all reached optimal state. The maximum proportion of hydrogen-production and total gas-production was 70.41% at 35°C. The optimal parameter was: the pH between 4.2-4.4 under the optimum temperature of 35°C.

Abstract: Hydrogen production by biomass gasification in supercritical water has special different distinct characteristics and advantage, this technology has become one of the international research focuses in the field of hydrogen energy. This paper gives a detail introduction of the process, characteristics and route of hydrogen production by biomass gasification in supercritical water, the biomass include glucose, cellulose methanol, and other waste effluents, the catalyst innovations and reactor development have also demonstrated, the prospects of are also presented in this paper.

Abstract: Microstructure and self-discharge characteristics of Ti-Zr-V-Cr-Ni-Ce hydrogen storage electrode have been investigated by XRD, FESEM-EDS and EIS measurements. Self-discharge properties indicate that the irreversible capacity loss is negative, which is different from that of AB₅ alloy electrode. The capacity loss can be divided in two parts, one is due to the deterioration of the hydrogen storage alloy, which will result in the decrease of discharge capacity, and the other is due to the continually activated, which will result in the increase of discharge capacity.

Abstract: A stand-alone renewable photovoltaic energy system can be used to meet the energy requirements of off-grid remote area applications. The excess photovoltaic energy with respect to load demand is transformed and stored as hydrogen gas via an electrolyzer. The stored hydrogen represents a long-term transportable form of fuel for fuel cell. To analyze the system performance and design the control strategy, it is necessary to develop a system model for the solar powered hydrogen production process. The operational characteristics of the photovoltaic array, the proton exchange membrane water electrolyzer (PEMWE), and the power converters are investigated. The maximum power output of the photovoltaic array is matched to the operating voltage of the PEMWE by the DC-DC converters. Simulation results of the PV-PEMWE hydrogen production process are discussed.

Abstract: Based on the integration of different systems and the comprehensive step utilization of energy, the system of hydrogen production by biomass gasification in supercritical water using concentrated solar energy has been coupled by using the combination of solar and biomass as an energy source. As a model compound of biomass, glucose was gasified in supercritical water at 25MPa and 873K, whether there is pre-heater water in the hydrogen production system was compared by the way of thermodynamic analysis. The results show that energy and exergy efficiency is high in the hydrogen production system with pre-heat water.

Abstract: A new Ni-BaCe_0.4Zr_0.4Nd_0.2O_3-δ （Ni-BZCN4）cermet membrane was used to separate hydrogen from mixed gas containing hydrogen. Hydrogen permeation properties of the membrane were investigated under various conditions. Hydrogen permeation flux increases with temperature. When the feed gas was moistened by 3% H₂O, the flux is about twice of that not moistened. And it reaches 0.29 cm³/ min.cm² at 900 °C when a wet 80% H₂/He feed gas was used. The permeation stability of Ni-BaCe_0.4Zr_0.4Nd_0.2O_3-δ membrane was investigated under atmospheres containing 30% CO₂ and H₂O. After 100 h operation, the membrane still keeps a steady permeation flux. These results suggest that the Ni-BZCN4 membrane is suitable for hydrogen separation from mixed gas containing H₂ and CO₂.

Abstract: This TiO₂ catalyst is modified by two means of doping and dye-sensitization to decompose the water into hydrogen under visible light irradiation in this paper. By exploring the mechanisms of the modification with two ways, it is found that the modification can make TiO₂ semiconductor with only UV photocatalytic activity become a catalyst with the visible-light activity. The experiments demonstrate that quantum efficiency and energy conversion efficiency of the doped catalyst is respectively 1.5% and 0.5%, and that of the sensitized catalyst is respectively 2.13% and 0.89%. By comparison the doped TiO₂ catalysts have better prospect in the application because of the instability of the sensitized catalyst.

Abstract: Different organics have different effects on the power generation of microbial fuel cell. A double-chamber Microbial Fuel Cell (MFC) was constructed to investigate organic matter degradation and power generation. Experiments were conducted using an initial phenol concentration of 500mg/L with different glucose concentrations (500 , 250 , and 100mg/L) as the MFC fuel . Results showed that maximum voltages decreased with the decrease of concentration of glucose and the maximum voltage was 434 mV. The cycle time were 170 , 146 ,141h respectively. Correspondingly , the maximal area power densities were 10.23 mw/m2,5.02mw/m²,3.15 mw/m². phenol and COD removal rate reached 28%-33.3% and 31.1%-54.74% respectively after one cycle. However, maximum voltage was 201 mV when using 500 mg/L phenol as sole fuel. The results indicated that phenol could be used in the MFC for generating power while at the same time effectively accomplishing biodegradation. The MFC technology may provide a new method to offset operating costs, making advanced remediation measures for difficult to degrade organic materials more affordable for practical applications.

Abstract: An overview of recent advances in hydrogen storage is presented in this review. The main focus is on metal hydrides, liquid-phase hydrogen storage material, alkaline earth metal NC/polymer composites and lithium borohydride ammoniate. Boron-nitrogen-based liquid-phase hydrogen storage material is a liquid under ambient conditions, air- and moisture-stable, recyclable and releases H₂ controllably and cleanly. It is not a solid material. It is easy storage and transport. The development of a liquid-phase hydrogen storage material has the potential to take advantage of the existing liquid-based distribution infrastructure. An air-stable composite material that consists of metallic Mg nanocrystals (NCs) in a gas-barrier polymer matrix that enables both the storage of a high density of hydrogen and rapid kinetics (loading in <30 min at 200°C). Moreover, nanostructuring of Mg provides rapid storage kinetics without using expensive heavy-metal catalysts. The Co-catalyzed lithium borohydride ammoniate, Li(NH3)4/3BH4 releases 17.8 wt% of hydrogen in the temperature range of 135 to 250 °C in a closed vessel. This is the maximum amount of dehydrogenation in all reports. These will reduce economy cost of the global transition from fossil fuels to hydrogen energy.

Abstract: This review summarizes efforts in developing proton exchange membranes (PEMs) with excellent electrochemical fuel cell performance prepared by SPAEK in proton exchange membrane fuel cell (PEMFC) applications. Over the past few decades, much polyelectrolyte has been extensively studied to improve the properties as alternatives with lower cost and considerable performances for PEMFC. Sulfonated poly(aryl ether ketone) (SPAEK), fell into this category, which offers the attribute of adjustable proton conductivity, excellent mechanical and thermal stability. The discussion will cover crosslinking, organic-inorganic nanocomposite, layer-by-layer approaches.