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991.
《International Journal of Hydrogen Energy》2019,44(26):13195-13204
It has been being an interesting challenge to develop novel electrocatalysts with advantageous nanostructures and thereby-improved catalytic performance for hydrogen evolution reaction (HER) over the past years. Herein, we report on the flower-like clusters of CoNiP nanofoils thickly grown on the randomly-interconnected reduced graphene oxide (rGO) nanosheets (CoNiP-NF/rGO) of 3-dimensional framework architecture, which has been successfully achieved via an optimized solvothermal process with Ni-doped ZIF-67 (Ni-ZIF-67) dodecahedral particles as the precursor and graphene oxide (GO) nanosheets as the substrate for the in-situ growth of flower-like CoNi-hydroxides nanofoils, as well as a following topotactic transformation in a controlled phosphorization. Benefiting from its distinctly advantageous nanostructures featured with extremely high specific surface area, enriched catalytic active sites and enhanced electronic transportation, the as-prepared CoNiP-NF/rGO exhibits an excellent electrocatalytic performance of HER with an onset overpotential of 33 mV, an overpotential of 82 mV at 10 mA cm−2, a Tafel slope of 37 mV dec−1 and a high chemical stability in acidic solutions. Such an advantageous nanostructure and its positive influences on the electrocatalytic performance are useful for the preparation of other nonprecious metal electrocatalysts. 相似文献
992.
《International Journal of Hydrogen Energy》2019,44(50):27421-27428
Electrochemical water splitting to hydrogen is considered as a promising approach for clean H2 production. However, developing highly active and inexpensive electrocatalysts is an important part of the hydrogen evolution reaction (HER). Herein, we present a multifaceted atom (sp2-and sp-hybridized boron) doping strategy to directly fine-modify the electronic structures of the active site and the HER performance by the density functional theory calculations. It is found that the binding strength between the Co atom and the B doped graphyne nanosheets can be enhanced by doping B atoms. Meanwhile, the Co@B1-GY and Co@B2-GY catalysts exhibit good thermodynamic stability and high HER catalytic activity. Interestingly, the Co@B2-GY catalyst has an ideal HER performance with the ΔGH* value of −0.004 eV. Moreover, the d-band center of the Co atoms is upshifted by the sp2-or sp-hybridized B dopants. The concentrations of the sp-hybridized B atoms have a positive effect on the electrons transformation of the Co atoms. The interaction between the H and Co atoms becomes strong with the increase of the concentrations of the sp-hybridized B atoms and thus the corresponding catalysts show sluggish HER kinetics. This investigation could provide useful guidance for the experimental groups to directly and continuously control the catalytic activity towards HER by precisely doping multifaceted atoms. 相似文献
993.
《International Journal of Hydrogen Energy》2021,46(72):35550-35558
The exploration of efficient catalysts toward hydrogen evolution reaction (HER) is still an urgent task. In this paper, Ni/Mo/Cu/C and Ni/Mo/C electrode were obtained by conventional pulse voltammetry, which acted as cathode in microbial electrolysis cells (MECs). The prepared samples are analyzed using SEM, XRD, XPS and electrochemical analysis techniques. Results indicated that the Ni/Mo/Cu coating has a rough and globular structure and presents high current density, a lower Tafel slope of 23.9 mV/dec than 30 mV/dec of Pt, which exceeds the electrochemical activity of Pt electrode. Its remarkably enhanced electrocatalytic activity is attributed to the high surface area, high conductivity as well as synergistic interaction among Ni, Mo and Cu. 相似文献
994.
《International Journal of Hydrogen Energy》2021,46(61):31202-31215
Direct methanol fuel cells (DMFCs) had been attracted considerable attention for its advantages of high energy density, simplified systems and readily transportation and storage of methanol. However, the notoriously sluggish kinetics of methanol oxidation reaction (MOR) of the anode reaction, had greatly affected the commercialization of DMFCs. On one hand, Pt based catalyst are still the most effective MOR catalysts, while the high cost caused by the high loadings of electrocatalyst to compensate the low MOR activity impedes the wide accessible of DMFCs. In addition, the occurrence of catalyst poisoning owing to the strong interaction between Pt and carbon monoxide (CO) generated during the MOR processing, further leading to the fast decay in the performance and stability of MOR electrocatalysts. Two-dimensional (2D) Pt based nanostructures is regarded to be one promising and effective class of MOR electrocatalysts, and attracted much attention due to the high electron mobility, highly exposed active sites, and extraordinary thermal conduction. In this review, the mechanism of MOR was firstly introduced, and then the synthesis conditions, structure characteristics and methanol oxidation performances both in acidic and alkaline dielectric of 2D Pt based nanocatalysts were introduced. Subsequently, we briefly analyzed the structural characteristics of 2D Pt based nanocatalysts and their advantages, including the low platinum loadings, high specific surface area and majority of atomic active sites exposed. Finally, the opportunities and challenges for designing of advanced 2D Pt based nanocatalysts was proposed and discussed. 相似文献
995.
《International Journal of Hydrogen Energy》2021,46(61):31253-31261
Nonprecious transition metals [e.g., cobalt (Co), iron (Fe), and zinc (Zn)], and nitrogen doped carbon materials are considered to be the most attractive alternatives to precious metal catalysts. Herein, Cobalt decorated nitrogen-doped carbon nanotubes were synthesized via a facile hydrothermal method and calcination. Benefiting from the N-doping, etching of Co nanoparticles to carbon nanotubes and synergistic effect between the components, the as-prepared Co/nitrogen-doped carbon nanotubes (Co-NCNT) displays a half-wave potential of 0.88 V (vs. RHE), a limiting current density of 5.6 mA cm−2, and electron transfer number of 3.9 in 0.1 M KOH. When applied in metal-air batteries, it delivered maximum power densities of 130.0 mW cm−2, 117.3 mW cm−2 and 58.6 mW cm−2 in alkaline Zn-air, Al-air batteries and neutral Mg-air batteries respectively, outperforming the commercial Pt/C. These demonstrate that the synthesized Co-NCNT is a promising candidate for ORR in metal-air batteries with both alkaline and neutral electrolytes. 相似文献
996.
《International Journal of Hydrogen Energy》2021,46(73):36348-36368
An elaborate numerical study with a validated LS-DYNA® immersed boundary method fluid-solid interaction code is used to characterize the influence of pre-detonation pressure, ignition point location and time duration on plastic deformation of thin steel plates subjected to hydrogen-oxygen gaseous detonation. Simulation relies on the modeling of detonation by chemical reaction kinetic and its propagation by conservative element solution element solver. Immersed boundary method is used to simulate the interface motion between the detonating gas and the deforming plate to facilitate the assessment of fluid pressure distribution on the plate surface. The numerical tool relates the pressure distribution and gaseous detonation parameters to the plate macroscopic deformation by employing multi-species reactive Euler's equations for the gas and assuming a Johnson-Cook material model for the plate. The numerical model simulated the experimental tests and a good agreement between them was obtained where specific features of gas detonation-driven forming were considered. With the confidence of the validation, the numerical model investigated the effects of different parameters such as the gaseous mixture initial temperature and combustion cylinder longitudinal capacity on overpressure-time history and strain-time history. It is demonstrated that the larger longitudinal capacity of combustion cylinder and more distant ignition point location have a great influence on increasing the detonation wave intensity. Eventually, the rate-dependent Johnson-Cook failure criterion was used to assess the failure state of plate under high-intensity detonations. 相似文献
997.
《International Journal of Hydrogen Energy》2021,46(73):36023-36036
Transition metal catalysts were supposed to be the most likely substitute for commercial noble metal catalysts, and the development of highly active and long-term catalyst for water splitting are the future trend. Herein, Ni rectangular nitrogen doped carbon nanorods@Fe–Co nanocubes (Ni-CNRs@Fe–Co cubes) were fabricated via a facile template-free method. This simple strategy not only realizes the structure tailoring, but also achieves high-quality nitrogen-doping. Specifically, nickel dimethylglyoxime [Ni(dmg)2] with rectangular rodlike structure was firstly synthesized by solution method, then metal-organic frameworks Fe–Co nanocube with different contents were loaded on rectangular carbon nanorods with polydopamine as the locating and the connecting agent, and finally Ni-CNRs@xFe-Co cubes were obtained by a one-step calcination. A series of electrochemical tests were researched on materials with different metal contents in the 1 M KOH solution. The Ni-CNRs@Fe–Co cubes show excellent electrocatalytic activity in the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER). For HER and OER, the Tafel slopes were 83.3 mV dec−1 and 71 mV dec−1, the onset potential were −167 mV and 1.62 V, and reached the current densities of 10 mA cm−2, the overpotential just needed 196 mV and 433 mV, respectively. This novel synthetic strategy will provide a template-free way for cheap electrocatalysts of non-precious metal for OER and HER. 相似文献
998.
H2 production via water–gas shift (WGS) reaction in a Pd membrane reactor prepared by the electroless plating technique (ELP) “organic–inorganic” method was investigated. Pd nanoparticles embedded polyethylene glycol (PEG) was used as a polymer template during the activation step. Gas permeation results showed an infinite selectivity for H2/N2 with a H2 flux of 0.004–0.016 mol/m2·s depending on operating conditions while it decreased until 0.0005 mol/m2·s for gas mixtures. Furthermore, WGS membrane reactor experiments showed a maximum CO conversion of 98.5% with a H2 recovery of 16% at 450°C. The membrane performance was consistent during WGS catalytic membrane reactors (CMR) tests, thereby confirming the stability of the obtained membrane. 相似文献
999.
Stoichiometry refers to conservation of atomic species. In this article, local refers to a point at the continuum level, global refers to the macroscopic balance level, and elementary refers to conservation of atomic species associated with distinct kinetic steps. The role of stoichiometry in the determination of the pivot matrix and the mechanistic matrix is presented. The elements of both these matrices are referred to as stoichiometric coefficients; however, both sets of coefficients are different and both play different roles in the analysis of chemical reactors. © 2011 American Institute of Chemical Engineers AIChE J, 2012 相似文献
1000.
从酯化反应的温度、底物浓度、用曲量、酯化时间几个方面着手,本着便于操作、能真实反映大曲酯化能力的相对大小、与生产实际相联系的原则,通过试验,选择合适的测定大曲酯化力的方法。 相似文献