| 1. |
- Hong, Jie, et al.
(author)
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Asymmetrically coupled co single-atom and co nanoparticle in double-shelled carbon-based nanoreactor for enhanced reversible oxygen catalysis
- 2023
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In: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 455
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Journal article (peer-reviewed)abstract
- Simultaneous construction of size-asymmetric metal single atoms and nanoparticle active sites in advanced and robust carrier materials is particularly important yet challenging for efficient reversible oxygen catalysis. Herein, a facile “chemical etching/in-Situ capture” synthesis strategy was developed to fabricate a unique double-shelled carbon-based nanobox integrated with size-asymmetric Co single-atom (CoSA) and metallic Co nanoparticle (CoNP) moiety. As expected, this well-managed catalyst product yielded remarkable bifunctional electrocatalytic performances in alkaline electrolytes, with a decent half-wave potential of 0.886 V for oxygen reduction reaction (ORR) and a small overpotential of 341 mV at 10 mA/cm2 for oxygen evolution reaction (OER). Besides, this nanobox catalyst served as a cost-effective and efficient oxygen electrode in the assembled rechargeable ZABs, exceeding the mixed electrocatalyst of expensive Pt/C-RuO2, in terms of the elevated peak power density of 239 mW/cm2, the promoted specific capacity of 770 mAh/gZn, as well as the appreciable charge–discharge cycle stability. Theoretical calculations revealed that the strong interaction between the delicate CoSA site and CoNP phase, could effectively optimize the adsorption and desorption energy barriers of reaction intermediates on the designed catalyst surface, thus achieving synergistic enhancement of electrocatalytic activity towards ORR and OER. This finding affords a feasible and effective strategy to achieve highly active and durable bifunctional catalysts for both fundamental research and practical rechargeable ZABs applications.
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| 2. |
- Li, Ziyao, et al.
(author)
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Atomic-level orbital coupling in a tri-metal alloy site enables highly efficient reversible oxygen electrocatalysis
- 2023
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In: Journal of Materials Chemistry A. - : Royal Society of Chemistry. - 2050-7488 .- 2050-7496. ; 11:5, s. 2155-2167
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Journal article (peer-reviewed)abstract
- Complex multi-metallic alloys with ultra-small sizes have received extensive attention in the fields of Zn-air battery and water splitting, because of their unique advantages including adjustable composition, tailorable active sites, and optimizable electronic structure. In this effort, an atomic-level orbital coupling strategy is presented to effectively regulate the electronic structures of ultra-small tri-metal Fe-Co-Ni nanoalloy particles confined in an N-doped carbon hollow nanobox. As expected, the optimal nanoalloy hybrid material exhibited notable bi-functional catalytic performances toward the oxygen reduction reaction (half-wave potential of 0.902 V) and oxygen evolution reaction (1.589 V at 10 mA cm−2) with a small ΔE of 0.687 V, exceeding the precious-metal-based and many previously reported catalysts. Furthermore, the as-assembled Zn-air device also displayed a superior specific capacity of 894 mA h g−1, a maximal power density of 247 mW cm−2, and impressive durability (over 100 hours). Ultraviolet photoelectron spectroscopy and density functional theory calculations revealed that the electronic structures could be finely tuned and optimized through ternary metal alloying, resulting in a suitable d-band center and advantageous interfacial charge-transfer, which in turn could effectively reduce the involved energy barriers in the electrocatalytic process and significantly boost its intrinsic activity of reversible oxygen catalysis. Thus, this work affords an effective method for the rational creation of bi-functional non-noble-metal-based electrocatalysts for sustainable energy technology.
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| 3. |
- Meng, Jingjing, et al.
(author)
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A smoothed finite element method using second-order cone programming
- 2020
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In: Computers and geotechnics. - : Elsevier. - 0266-352X .- 1873-7633. ; 123
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Journal article (peer-reviewed)abstract
- In this paper, a new approach abbreviated as SOCP-SFEM is developed for analysing geomechanical problems in elastoplasticity. The SOCP-SFEM combines a strain smoothing technique with the finite element method (FEM) in second-order cone programming (SOCP) and thereby inherits the advantages of both the smoothed finite element method (SFEM) and the SOCP-FEM. Specifically, the low-order mixed element can be used in the SOCP-SFEM without volumetric locking issues and the singularity associated with some typical constitutive models (e.g. the Mohr-Coulomb model and the Drucker-Prager model) is no longer a problem. In addition, the frictional and the cohesive-frictional interfaces can be implemented straightforward in the developed SOCP-SFEM owing to the adopted mixed variational principle and the smoothing technique. Furthermore, the multiple contact constraints, such as a cohesive interface with tension cut-off which is commonly used for analysing the bearing capacity of a pipeline buried in clays, can be simulated with little extra effort. To verify the correctness and robustness of the developed formulation for SOCP-SFEM, a series of benchmarks are considered where the simulation results are in good agreements with the analytical solutions and the reported numerical results.
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| 4. |
- Meng, Jingjing, et al.
(author)
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A static discrete element method with discontinuous deformation analysis
- 2019
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In: International Journal for Numerical Methods in Engineering. - : John Wiley & Sons. - 0029-5981 .- 1097-0207. ; 120:7, s. 918-935
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Journal article (peer-reviewed)abstract
- For discrete element methods (DEMs), integrating the equation of motion based on Newton's second law is an integral part of the computation. Accelerations and velocities are involved even for modeling static mechanics problems. As a consequence, the accuracy can be ruined and numerous calculation steps are required to converge. In this study, we propose a static DEM based on discontinuous deformation analysis (DDA). The force of inertia is removed to develop a set of static equilibrium equations for distinct blocks. It inherits the advantages of DDA in dealing with distinct block system such as jointed rock structures. Furthermore, the critical numerical artifact in DDA, ie, artificial springs between contact blocks, is avoided. Accurate numerical solution can be achieved in mere one calculation step. Last but not the least, since the method is formulated in the framework of mathematical programming, the implementation can be easily conducted with standard and readily available solvers. Its accuracy and efficiency are verified against a series of benchmarks found in the literature.
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| 5. |
- Meng, Jingjing, et al.
(author)
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Three-dimensional spherical discontinuous deformation analysis using second-order cone programming
- 2019
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In: Computers and geotechnics. - : Elsevier. - 0266-352X .- 1873-7633. ; 112, s. 319-328
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Journal article (peer-reviewed)abstract
- In this paper, a new formulation of three-dimensional spherical discontinuous deformation analysis (DDA) based on second-order cone programming has been proposed. Artificial springs with open-close iteration used in classic DDA have been removed, given that improper stiffness parameters might cause numerical problems. Furthermore, to account for irregular granular shapes, a rolling resistance model is incorporated in the variational formulation. The proposed formulation can be cast into a standard second-order cone programming program, which can be solved using efficient off-the-shelf optimisation solvers. The proposed approach is validated by a series of numerical examples.
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| 6. |
- Nie, Zhicheng, et al.
(author)
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Tailoring the d-band center by intermetallic charge-transfer manipulation in bimetal alloy nanoparticle confined in N-doped carbon nanobox for efficient rechargeable Zn-air battery
- 2023
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In: Chemical Engineering Journal. - : Elsevier. - 1385-8947 .- 1873-3212. ; 463
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Journal article (peer-reviewed)abstract
- In this effort, the electronic-structure modulation strategy through nano-alloying was rationally designed to fabricate Fe-Ni alloy particles embedded in an N-doped carbon nanobox. The as-developed catalyst outperformed the commercialized noble-metal benchmarks with a decent half-wave potential of 0.891 V for ORR and a small overpotential of 325 mV at 10 mA/cm2 for OER both in 0.1 M KOH solution. Beyond that, a highly-efficient regenerative Zn-air battery was also successfully constructed, evidenced by a small potential gap of 0.664 V (between Ej=10 and E1/2), a high specific capacity of 763 mAh/g, a large peak power density of 270 mW/cm2, and robust stability. Ultraviolet photoelectron spectroscopy and theoretical simulation confirmed that the alloying of Ni into Fe could well manipulate the electronic structure, leading to favorable intermetallic charge-transfer and then downshifting the d-band center of Fe adsorption sites, all of which help to significantly lower the reaction barriers of the involved intermediates during the electrocatalytic ORR/OER processes.
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| 7. |
- Nie, Zhicheng, et al.
(author)
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Vacancy and doping engineering of Ni-based charge-buffer electrode for highly-efficient membrane-free and decoupled hydrogen/oxygen evolution
- 2023
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In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 642, s. 714-723
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Journal article (peer-reviewed)abstract
- The realization of the membrane-free two-step water electrolysis is particularly important yet challenging for the low-cost and large-scale supply of hydrogen energy. In this effort, Co-doped Ni(OH)2 nanosheets were successfully anchored onto the nickel foam (NF) substrate through the in-situ growth of metal-organic frame material and the subsequent alkali-etching technique. Using the well-regulated Co-doping Ni(OH)2@NF electrodes as a charge mediator, electrochemical hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) were decoupled on time scales, thus affording a membrane-free two-step route for H2 and O2 productions. In this architecture, the first HER process on the cathode could be maintained for 1300 s at a current of 100 mA, while the corresponding Ni(OH)2 charge mediator was simultaneously oxidized to NiOOH, with a decent cell voltage of 1.542 V. The subsequent OER process involved a reduction/regeneration of Ni(OH)2 (from NiOOH to Ni(OH)2) and an anodic O2-production, with an operating voltage of 0.291 V. Moreover, the Ni-Zn battery assembled through the combination of NiOOH and Zn sheet could replace the second step of OER to achieve the coupling of continuous H2-production and battery discharge, thus also providing a new way for hydrogen production without an external power supply. Experiment and theoretical calculations have shown that the cobalt-doping not only improved the conductivity of the charge-buffer electrode, but also shifted its redox potential cathodically and boosted the adsorption affinity of the buffer medium to OH– ions, both contributing to promoted HER and OER activity. Therefore, this decoupled water electrolysis device affords a promising pathway to support the efficient conversion of renewables to hydrogen.
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| 8. |
- Yang, R., et al.
(author)
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Optimal geotechnical site investigations for slope design
- 2019
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In: Computers and geotechnics. - : Elsevier. - 0266-352X .- 1873-7633. ; 114
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Journal article (peer-reviewed)abstract
- Site investigation in combination with field and laboratory testing, plays a vital role in characterizing the soil profile for geotechnical design in order to reduce uncertainty. In spite of this, site investigations are often limited in scope due to high costs. In this paper, conditional random fields are used to examine the influence of soil strength mean, standard deviation and spatial correlation length on the risk of slope design failure for different levels of site investigation scope. An undrained slope example is used to illustrate how the proposed approach can be used to assess the risk reduction that can be obtained as the scope of a site investigation is increased. By combining the cost of site investigation with the cost of slope failure, the results indicate that there exists an optimal site investigation scope, beyond which the cost of additional boreholes does not justify the cost savings due to reduced slope failure risk.
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| 9. |
- Zhang, Lei, et al.
(author)
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Nickel-induced charge redistribution in Ni-Fe/Fe3C@nitrogen-doped carbon nanocage as a robust Mott-Schottky bi-functional oxygen catalyst for rechargeable Zn-air battery
- 2022
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In: Journal of Colloid and Interface Science. - : Elsevier. - 0021-9797 .- 1095-7103. ; 625, s. 521-531
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Journal article (peer-reviewed)abstract
- Designing earth-abundant and advanced bi-functional oxygen electrodes for efficient oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are extremely urgent but still ambiguous. Thus, metal-semiconductor nanohybrids were developed with functionally integrating ORR-active Ni species, OER-active Fe/Fe3C components, and multifunctional N-doped carbon (NDC) support. Expectantly, the resulted NDC nanocage embedded with Ni-Fe alloy and Fe3C particles, as assembled Mott-Schottky-typed catalyst, delivered a promoted half-wave potential of 0.904 V for ORR and a low overpotential of 315 mV at 10 mA/cm2 for OER both in alkaline media, outperforming those of commercial Pt/C and RuO2 counterparts. Most importantly, the optimized Ni-Fe/Fe3C@NDC sample also afforded a peak power density of 267.5 mW/cm2 with a specific capacity of 773.8 mAh/gZn and excellent durability over 80 h when used as the air electrode in rechargeable Zn-air batteries, superior to the state-of-the-art bi-functional catalysts. Ultraviolet photoelectron spectroscopy revealed that the introduction of Ni into the Fe/Fe3C@NDC component could well manipulate the electronic structure of the designed electrocatalyst, leading to an effective built-in electric field established by the Mott-Schottky heterojunction to expedite the continuous interfacial charge-transfer and thus significantly promote the utilization of electrocatalytic active sites. Therefore, this work provides an avenue for the designing and developing robust and durable Mott-Schottky-typed bi-functional catalysts for promising energy conversion.
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