Hydrogen atom absorption in hydrogen-covered Pd(110) (1 × 2) missing-row surface

The absorption of H atom in H-covered Pd(110) (1 × 2) missing-row surface is investigated using density functional theory based calculations. For 1.5 monolayer H coverage, interaction among the adsorbed H atoms is found to be negligible and was verified by analyzing the electronic structure of the system and by comparing the calculated binding energies with low H coverage case. Neither the monoatomic absorption of H nor the assistance from the initially adsorbed H atom explains the experimentally observed presence of subsurface H in Pd(110) at high H coverage. Instead, H absorption is realized through the assistance of incoming H atoms from vacuum. The absorption of H in the H-covered surface is non-activated while the dissociation of H₂ is the rate-limiting process. Dissociation on ridge site is energetically more preferred than on trough site and the difference in the activation barrier is elucidated by investigating the electronic structures of the system.     

Physical characteristics and rate performance of (CFx)n (0.33 < x < 0.66) in lithium batteries

Sub-fluorinated graphite fluorides (CF_x)_n compounds, 0.33 < x < 0.63 were prepared from natural graphite and characterized by TGA, SEM-EDX and XRD. Their cathode behavior in lithium batteries was investigated under different discharge rates and compared to commercial petroleum coke based (CF)_n. At low discharge rate, the energy density increases with the fluorine content x. However, at higher rates, sub-fluorinated compounds performed better than commercial (CF)_n. The result is discussed with relation to higher electrical conductivity of sub-fluorinated compounds.     

Modeling of the equilibrium moisture content (EMC) of Miscanthus (Miscanthus × giganteus)

The desorption isotherms of miscanthus, Miscanthus × giganteus (stems and leaves) were determined separately by using the saturated salt solutions method at three temperatures (25, 50 and 70 °C) within a range from 5 to 90% relative humidity. Experimental curves of desorption isotherms were fitted to Modified Henderson, Modified Halsey, Modified Oswin and Modified Chung-Pfost models and evaluated by Residual Sum of Squares (RSS), Standard Error Estimation (SEE) and Mean Relative Deviation (MRD) methods. The Modified Oswin model was found to be the most suitable for describing the correlation between equilibrium moisture content, relative humidity and temperature.     

Xylose fermentation to biofuels (hydrogen and ethanol) by extreme thermophilic (70 °C) mixed culture

Combined biohydrogen and bioethanol (CHE) production from xylose was achieved by an extreme thermophilic (70 °C) mixed culture. Effect of initial pH, xylose, peptone, FeSO₄, NaHCO₃, yeast extract, trace mineral salts, vitamins, and phosphate buffer concentrations on bioethanol and biohydrogen yield was investigated in batch experiments. Results obtained showed that initial pH, concentration of xylose, peptone, and FeSO₄ significantly affected biohydrogen and bioethanol production, while the concentration of NaHCO₃ was only significant for bioethanol production. By changing cultivation conditions the culture could be directed to mainly produce ethanol with maximum ethanol yield of 1.60 mol ethanol/mol-xylose corresponding to 95.8% of the theoretical ethanol yield based on degradation of xylose through ethanologenic pathway, or mainly hydrogen with maximum hydrogen yield of 1.84 mol H₂/mol-xylose corresponding to 55% of the theoretical hydrogen yield based on acetate metabolic pathway. An empirical model was established to reveal the quantitative effect of factors significant for biohydrogen (quadratic model) production and for bioethanol (linear model) production. Changes in hydrogen/ethanol yields observed were due to the shift of the metabolic pathway between ethanol or hydrogen production, rather than changes in bacterial community composition at genus level. Thermoanaerobacter related bacteria were found to be the dominant hydrogen/ethanol producers.     

ICS solar systems with horizontal (E–W) and vertical (N–S) cylindrical water storage tank

The use of a horizontal cylindrical water storage tank contributes to pressure resistant, low height and efficient ICS solar systems. These systems can satisfactorily achieve water heating when the cylindrical storage tank is combined with stationary CPC or involute type curved reflectors. The diameter of the cylindrical storage tank determines the length of the reflectors, the system depth and the ratio of the stored water per aperture area. In these solar systems the storage tank can be partially thermally insulated to suppress thermal losses from it to the ambience. We constructed four experimental models with truncated symmetric CPC reflectors, two with 90° and other two with 60° of acceptance angle, half of them without and half with a 1/4 thermally insulated storage tank cylindrical surface. In addition, we constructed two ICS systems with involute reflectors, with acceptance angle 180°, one without and the other one with a 1/4 thermally insulated storage tank. The six ICS systems were tested under the same weather conditions and without water drain, to determine their stored water temperature variation, mean daily efficiency and thermal losses during night. The results showed that CPC reflectors contribute to efficient operation of systems day and night, while involute reflectors mainly to the water heat preservation during night.     

Highly charged and stable cross-linked polysulfone alkaline membrane for fuel cell applications: 4,4,-((3,3&#x27;-bis(chloromethyl)-(1,1&#x27;-biphenyl)-4,4-diyl)bis(oxy))dianiline (BCBD) a novel cross-linker

Alkaline membrane (AM) shows fast transport of OH⁻ towards the anode, separates both electrodes, and prevents fuel cross-over. To achieve good membrane conductivity and performance, high concentration of positively charged groups (quaternary ammonium) is an essential requirement, which also leads excessive swelling and mechanical instability of the AMs. Further, directly grafted quaternary ammonium (QA) with main polymer chain substitution and/or elimination reactions under strong alkaline environment. To avoid above-mentioned problems, we report preparation of cross-linked chloromethylated polysulfone based AM using (4,4^,-((3,3′-bis(chloromethyl)-[1.1′-biphenyl]-4,4-diyl)bis(oxy))dianiline) (BCBD), a multi-functional novel cross-linking agent. Reported strategy compensates 2 mol of chloromethyl groups consumed during cross-linking, but additional functional groups (4 mol) with cross-linking agent. These AMs are designed to avoid the nucleophilic substitution (S_N²) (grafting quaternary ammonium (QA) groups at benzylic position), and Hofmann elimination (E²) reactions (unavailability of β-H), under strong alkaline environment. Effective cross-linking has been confirmed by spectral analysis, and improves membrane stabilities and fuel cell performance. Single-cell alkaline membrane fuel cell (AEMFC) performance of most suitable (CR-QPS-03) membrane, showed comparatively high performance (open circuit voltage (OCV): 0.813 V, maximum power density: 103.6 mW/cm² at 260.0 mA/cm²) in compare with Nafion 117 membrane (OCV: 0.682 V, maximum power density: 63.36 mW/cm² at 220.0 mA/cm²) under similar experimental conditions.     

Canada’s constitutional separation of (wind) power

This paper investigates the impact that a federal government structure has on strategic selection of renewable energy policy instruments. The context for this study centers on wind power development in Canada. Canada is a nation that is blessed by all the attributes necessary to catalyze global leadership in installed wind power capacity. Unfortunately, the constitutional separation of powers that underpins Canada’s federal system impedes the creation of a national wind power development strategy because Canada’s provinces have constitutional authority over electricity governance. The insights gleaned from the case study are used to develop a conceptual framework for understanding the impact that federal structure has on policy instrument selection and efficacy under areas of federal, regional and concurrent policy jurisdiction. Finally, this framework is re-applied to identify specific approaches the Canadian federal government could take to resolve what currently amounts to be a fragmented, ineffective approach to wind power development planning.     

Fundamentals of electrochemistry (Ⅳ) --Electrode kinetics

电极过程动力学对电化学过程起着支配作用,研究成果广泛用于化学工业,能源领域,材料科学和环境保护等领域.电极过程主要由扩散传质,传荷过程以及表面吸附/脱附步骤构成.电活性物质从溶液主体到电极表面的传质过程包括对流,扩散和电迁移三种基本形式.电流-电势关系是表征电极反应动力学的基本途径,并在特定的电极条件下,可以推导得出Tafel半对数极化曲线公式和Butler-Volmer电极动力学公式.广义的表面转化过程包含了前置的表面转化步骤和后置的表面转化步骤.此外,利用流体力学计算能够反映电极表面流体流动对旋转圆盘电极过程的传质影响.通过对上述基本概念的总结与归纳,能够加深对电化学核心内容的把握,有利于研究开发新型应用电化学技术.     

Hydrogen storage and cyclic properties of V60Ti(21.4+x)Cr(6.6−x)Fe12 (0 ≤ x ≤ 3) alloys

Hydrogen storage and cyclic properties of V₆₀Ti_(21.4+x)Cr_(6.6−x)Fe₁₂ (0 ≤ x ≤ 3) alloys were investigated systematically. All alloys were composed of single BCC phase and exhibited good activation performance. V₆₀Ti_22.4Cr_5.6Fe₁₂ showed the highest desorption capacity of 2.12 wt% with the plateau pressure of 0.061 MPa. In the absorption–desorption cycle tests, both the hydrogen desorption capacity and the micro-strain of V₆₀Ti_22.4Cr_5.6Fe₁₂ alloy showed exponential relationship with the increase of cycle numbers, which indicated that the micro-strain induced and thereafter accumulated during the absorption–desorption cycles might lead to the decrease of the desorption capacity.     

The Formation of Nano—Size SiO2 Thin Film on an Aluminum Plate with Hexamethyldisilazane（HMDSA）and Hexamethyldisiloxane（HMDSO）

This study is using HMDSA(C6H19NSi2)or HMDSO(C6H18OSi2) vapor into C3H8/air premixed flames to form SiO2 thin film on the surface of an aluminum palte.With the addition of HMDSO or HMDS to premixed flames,an orange secondary flame or a flame brush appeared and was contributed to the formation of SiO2 particles.Based upon the EDS,XPS and FTIR analysis ,it is believed that the synthesized products consist of mainly SiO2 and a small amount of SiO,The pure SiO2 crystal structure,was proved by XRD analysis,which may form form the SiO2 amorphous structure after high temperature(1300℃) thermal treatment.The nano-size SIO2 particles,which ranged form 2.5-25nm,are proved by analysis of the BET and TEM.A 2-D CFD-RC code with 12 reduced chemical reaction mechanism.based upon the SIMPLER procedure,was successfully employed to predict the flame temperature and both of the SiO2 and SiO concentration profiles.Compared with the experimental results,the calculated temperature profiles in the post-flame region are in good agreement with the measured data and observation phenomena.