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1.
The Langmuir adsorption isotherm of the over-potentially deposited hydrogen (OPD H) for the cathodic H 2 evolution reaction (HER) at the Pt–Rh (Pt:Rh; 80:20 wt%) alloy/0.5 MH 2SO 4 aqueous electrolyte interface has been studied using cyclic voltammetric and ac impedance techniques. The behavior of the phase shift (0°−φ90°) for the optimum intermediate frequency can be linearly related to that of the fractional surface coverage (1θ0) of the OPD H for the cathodic HER at the interface. The phase-shift profile (−φ vs. E) for the optimum intermediate frequency, i.e., the phase-shift method, can be used as a new electrochemical method to determine the Langmuir adsorption isotherm (θ vs. E) of the OPD H for the cathodic HER at the interface. At the Pt–Rh alloy electrode interface, the equilibrium constant ( K) and the standard free energy (Δ Gads) of the OPD H are 2.2×10 −4 and 20.9 kJ/mol, respectively. At the steady state, the behaviors of the cyclic voltammogram and the Langmuir adsorption isotherm of the OPD H for the cathodic HER at the Pt–Rh alloy electrode interface are similar to those of the pure Pt electrode interfaces. At the steady state, the effect of Rh on the OPD H for the cathodic HER can be neglected at the Pt–Rh (Pt:Rh; 80:20 wt%) alloy/0.5 MH 2SO 4 aqueous electrolyte interface. 相似文献
3.
The Frumkin isotherm provides information about the atomic behaviors of hydrogen (H) and deuterium (D) on the electrocatalyst surface. However, it cannot be obtained easily by the conventional electrochemical methods, owing to the similar electrochemical behaviors of the under- and over-potential deposition of H and D (UPD H, OPD H, UPD D, and OPD D) and the numerous overlapping factors at the electrocatalyst interface. In this study, the Frumkin isotherms for the discharge reactions of the OPD H and OPD D in the Volmer steps, isotopic shift of these isotherms, and equilibrium isotope effect (EIE) at the interfaces of Pd/alkaline (regular and heavy water: H 2O and D 2O) solutions are precisely determined by the phase-shift method. The interaction parameter ( ɡ) and equilibrium constant ( K) are 6.6 and 9.7 × 10 ?6 exp (?6.6θ) mol ?1, respectively, for OPD H and 8.7 and 1.1 × 10 ?6 exp (?8.7θ) mol ?1, respectively, for OPD D, where θ is the fractional coverage (0 ≤ θ ≤ 1). In the range of θ (0 ≤ θ ≤ 1), the standard Gibbs energy (Δ Gθ0) of OPD D is 5.4–10.6 kJ mol ?1 higher than that of OPD H. The EIE values increase from 8.8 to 72.1 with increasing θ and are extraordinarily high compared to those at other Pt-group metal interfaces. The EIE values at the interfaces of Pt-group metal/alkaline (H 2O and D 2O) solutions decrease in the following order: Pd >> Pt–Ir alloy > Pt > Ru > Ir and Rh. We expect that the Frumkin isotherms of OPD H and OPD D and the related EIE established in this study will be a useful and effective tool for studying the isotope effects at various electrocatalyst interfaces. 相似文献
4.
To reduce the greenhouse effect and as a fuel alternatives hydrogen is used as a secure and clean energy. But there are some challenges in the storage of hydrogen energy, the present accurate dynamics of adsorption and release of hydrogen. We report the adsorption and desorption of hydrogen atoms (up to eight) on the ZrAl m (m = 3 to 7) clusters using density functional theory within B3PW91/LANL2DZ basis sets in the GAUSSIAN 09 package. Adsorption energy for per hydrogen atom in all clusters is found in the range of ?2.5 eV to ?3.3 eV, which shows the chemisorption of hydrogen on the ZrAl m clusters. Change in the DOS with number of hydrogen is attributed to the charge transfer between the ZrAl m clusters and hydrogen atoms. Highest HOMO-LUMO gap of 3.055 eV is found for the ZrAl 3H 7 cluster which indicates that the ZrAl 3H 7 cluster is chemically more stable. Work function values for hydrogen doped clusters are in the range of 3.5 eV–4.4 eV which suggests the low optical absorption in considered clusters. The calculated enthalpy difference further confirms the chemisorption of hydrogen on ZrAl m clusters ZrAl 3H n and ZrAl 7H n(for n = 1 to 5 and 7) are more exothermic than other considered clusters. Desorption energies per hydrogen for these clusters are found lower than the some of the best catalytic clusters Pd 13 and Pt 13 indicating more catalytic active nature. 相似文献
6.
A well-designed control system with a high utilization ratio of hydrogen and a fast filling speed are two critical objectives to ensure the reduction of cost and time required in the refueling process. In this paper, the popular three-stage refueling process is modeled with the aim to address both objectives. Using the real gas law of hydrogen, the utilization ratio of hydrogen filling is analyzed and the filling flowrate and time of each stage are evaluated. A multi-objective iterative optimization model is established and an optimization algorithm for the filling process is proposed to achieve both fast refueling and high utilization. Numerical results can be applied to the optimization of an actual hydrogen filling process. Besides, the tests show that an optimized control method can significantly improve the utilization ratio and allow refueling in a widely acceptable time. 相似文献
7.
In this study, a mixed numerical model is established to simulate the production performance of gaseous compound of hydrogen and carbon in shale reservoir. Estimated ultimate recovery (EUR) and stable production life (SPL) of gaseous compound of hydrogen and carbon are affected by reservoir parameters and production control parameters, such as Langmuir pressure, Langmuir volume, critical desorption pressure, fracture half length, permeability in stimulated reservoir volume (SRV) area, bottom hole flow pressure and production of gaseous compound of hydrogen and carbon. Therefore, in the later research, in order to reduce the number of numerical experiments, the orthogonal experimental method is used to optimize the influence of hydrocarbon ERU and SPL, and analyze the main control factors affecting these two indices at the same time. The purpose of this paper is to optimize the production of hydrocarbons by orthogonal experimental method and find the main controlling factors affecting the production of compound of hydrogen and carbon. Two groups of orthogonal experiments were designed to find the best scheme in the process of compound of hydrogen and carbon development. The calculative results show that the output of hydrogen and carbon compounds has a highly significant impact on SPL, Langmuir volume and capability in SRV have a significant impact, and Langmuir pressure Critical destruction pressure and hydraulic fracture half-length had no significant effects. 相似文献
9.
Two different Co–S compounds with enhanced hydrogen storage properties, Co 9S 8 and CoS 2, were prepared by ball-milling mixtures of Co metal and S powder. X-ray diffractometry, scanning electron microscopy and transmission electron microscopy were used to show that specific molar ratios of Co:S and ball-milling speeds and times result in pure Co 9S 8 and CoS 2, thus overcoming a long-standing inability to obtain pure Co–S compounds via ball-milling. A galvanostatic charge–discharge process and cyclic voltammetry measurements showed that the as-obtained Co 9S 8 and CoS 2 nanoparticles have enhanced electrochemical hydrogen storage capacities of 1.79 and 1.57 wt% hydrogen, respectively, which are higher than those previously reported. In addition, based on the corresponding X-ray photoelectron spectroscopy and cyclic voltammetry measurements, a new electrochemical hydrogen storage mechanism for the two Co–S compounds was proposed and discussed. 相似文献
10.
秸秆类生物质进行本酶解糖化,而后进行光合细菌产氢过程中,确定其纤维素酶酶负荷是秸秆酶法预处理的关键步骤.确定其酶负荷首先要对纤维素酶酶活力进行测定,酶活力的测定有多种方法可以选用.将多种纤维素酶活测定方法进行融合,滤纸酶活力可以代表纤维素酶的总体酶活力,且分光光度计法大大缩短了酶活力测定所需要的时间,且具有较商的精确度... 相似文献
11.
在海上录井随钻解释工作开始时间并不长、解释符合率还不是很高的情况下,如何捕捉钻井中的油气显示层,开展定量评价油气层,特别是不漏掉薄层、轻质油气层及低电阻率油气层,具有极其重要的意义。Reserval气体比率法利用轻烃与中烃比率(RLM)、轻烃与重烃比率(RLH)以及重烃与中烃比率(RHM)曲线的组合形态,可以指示不同的储集层流体性质,甚至可根据它们的变化很容易地辨认出油水界面,较好地解决了渤海海上常用方法无法解释的问题。利用以Reserval气体比率法为主,结合其他录井等相关资料,对渤海探区BZ油田已钻的19口井进行解释评价,结果显示:气层解释符合率100%,油层解释符合率87.3%,油水同层符合率62.5%,水层符合率73.7%,总体符合率达到83.9%。Reserval气体比率法的应用,提高了渤海轻质油、凝析油、低电阻率油层的解释精度。 相似文献
12.
Hydrogen evolution reaction following Volmer–Heyrovsky–Tafel mechanism and not under diffusion control can be characterized using Tafel polarization and alternating current admittance data at various frequencies and at various overpotentials. Such reaction has four independent kinetic parameters. One empirical constant related to charge required for complete surface coverage is also involved. In case of systems where only one time constant (related to charging/discharging of electrical double layer) is discerned, Volmer–Heyrovsky mechanism is assumed. Such systems have three independent kinetic parameters. Experimental data may provide maximum two independent conditions at a less cathodic overpotential and maximum one independent condition at a more cathodic overpotential. A new approach to determine kinetic parameters utilizing these data and neglecting Heyrovsky and Tafel backward reaction rates has been proposed. The conditions involved are coupled non-linear equations. Uncoupled non-linear equations have been derived and iterated using Newton–Raphson method. The approach has been validated using literature data. The graphical relationships between experimental parameters and kinetic parameters have also been shown. 相似文献
13.
An original hybrid membrane-catalytic reactor (HMCR) was developed for the co-production of syngas and ultrapure hydrogen from fossil and renewable organic sources (methane and ethanol), as well as from synthetic feedstock (dimethyl ether) via dry and steam reforming. HMCR is a facility in which a porous ceramic catalytic converter prepared by self-propagating high-temperature synthesis (SHS) is integrated with a hydrogen-selective palladium-containing membrane. Due to separation of hydrogen from the reaction site and according to Le Chatelier-Brown principle it enables reforming to proceed effectively under milder temperature conditions as compared to a conventional reactor with a stationary bulk catalyst bed. On the basis of HMCR there can be developed mobile and small-size ultrapure hydrogen production units for fine processes of organic synthesis and electricity generation. 相似文献
14.
The hydrogen sorption and desorption behavior in spherical powder of pure titanium used for additive manufacturing have been investigated. The dependencies of oxide dissolution time and hydrogen sorption rate on pressure and temperature have been obtained. The main regularities of phase formation in titanium powder during hydrogenation until hydrogen concentration 4 wt% have been showed. The peculiarities of hydrogen desorption from the spherical powder of titanium with hydrogen concentration 4 wt% have been demonstrated. 相似文献
15.
Due to the increasingly serious environmental issues and continuous depletion of fossil resources, the steel industry is facing unprecedented pressure to reduce CO 2 emissions and achieve the sustainable energy development. Hydrogen is considered as the most promising clean energy in the 21st century due to the diverse sources, high calorific value, good thermal conductivity and high reaction rate, making hydrogen have great potential to apply in the steel industry. In this review, different hydrogen production technologies which have potential to provide hydrogen or hydrogen-rich gas for the great demand of steel plants are described. The applications of hydrogen in the blast furnace (BF) production process, direct reduction iron (DRI) process and smelting reduction iron process are summarized. Furthermore, the functions of hydrogen or hydrogen-rich gas as fuels are also discussed. In addition, some suggestions and outlooks are provided for future development of steel industry in China. 相似文献
16.
Hydrogen can be a promising clean energy carrier for the replenishment of non-renewable fossil fuels. The set back of hydrogen as an alternative fuel is due to its difficulties in feasible storage and safety concerns. Current hydrogen adsorption technologies, such as cryo-compressed and liquefied storage, are costly for practical applications. Metal-organic frameworks (MOFs) are crystalline materials that have structural versatility, high porosity and surface area, which can adsorb hydrogen efficiently. Hydrogen is adsorbed by physisorption on the MOFs through weak van der Waals force of attraction which can be easily desorbed by applying suitable heat or pressure. The strategies to improve the MOFs surface area, hydrogen uptake capacities and parameters affecting them are studied. Hydrogen spill over mechanism is found to provide high-density storage when compared to other mechanisms. MOFs can be used as proton exchange membranes to convert the stored hydrogen into electricity and can be used as electrodes for the fuel cells. In this review, we addressed the key strategies that could improve hydrogen storage properties for utilizing hydrogen as fuel and opportunities for further growth to meet energy demands. 相似文献
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