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31 results on '"Duan, Congwen"'

12. CNTs-Pd as Efficient Bidirectional Catalyst for Improving Hydrogen Absorption/Desorption Kinetics of Mg/MgH2

Author

Duan, Congwen, Wu, Jinhui, Liang, Poqian, Wang, Haimei, Qu, Ting, Fan, Yuchen, Su, Yaohua, Su, Zhaohua, Hu, Lianxi, and Wu, Ying

Abstract

The hydrogen storage potential and cost-effectiveness of MgH2have rendered it a desirable material for hydrogen storage. However, its application has been hindered by limitations in thermal stability and dehydrogenation kinetics. In this study, the carbon nanotube-Pd bifunctional catalyst was prepared by using hydrothermal and calcination technology, significantly improving the kinetics of Mg/MgH2during hydrogen adsorption/desorption. The activation energy for the Mg@ CNTs-Pd was reduced to 42.73 kJ/mol, as determined by fitting the Avrami–Erofeev model with the Arrhenius equation. Additionally, the activation energy during dehydrogenation was found to be 73.98 kJ/mol based on the Johnson–Mehl–Avrami–Kolmogorov equation and the Arrhenius equation. It is worth noting that the dynamic enhancement persists even after 10 cycles. This groundbreaking research has paved the way for potential applications of MgH2as a hydrogen storage material, providing it with broader development opportunities.

Published
2024
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18. Mechanochemical synthesis of the α-AlH3/LiCl nano-composites by reaction of LiH and AlCl3: Kinetics modeling and reaction mechanism

Author

Ma Jinlong, Zhang Jing-hong, Hu Lianxi, Cao Yizheng, Duan Congwen, Zhang Yu-ling, and Fu Dong

Subjects
Reaction mechanism, Materials science, Renewable Energy, Sustainability and the Environment, Kinetics, Nucleation, Energy Engineering and Power Technology, 02 engineering and technology, Activation energy, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, 01 natural sciences, Chemical reaction, Isothermal process, 0104 chemical sciences, Fuel Technology, Chemical engineering, Reagent, Desorption, 0210 nano-technology
Abstract

Mechanochemical activation-assisted synthesis, compared to conventional wet methods, exhibits advantages such as higher chemical homogeneity and better quality of the resulting nano-crystals, in preparing nano-sized aluminum hydride (AlH3). Solid/liquid state milling is effective and convenient for production of α-AlH3/LiCl nano-composites through a mechanochemical reaction of LiH and AlCl3 in [2-Eim] OAc. However, the kinetics of this process has not been thoroughly studied. In this work, we studied the kinetics of mechanochemical synthesis of α-AlH3/LiCl nano-composite to understand the reaction process and find the optimum milling parameters (including shortest time to achieve high-quality product). We performed isothermal desorption tests for as-milled samples at 80 °C. Structures of the products were analyzed using X-ray powder diffraction. Johnson-Mehl-Avrami (JMA) model was adopted to describe the process, which contains transformation fraction and chemical reaction controlled regime. Kinetics of mechanochemical reaction at the beginning was limited by diffusion rate of the reagent, and later controlled by nucleation of AlH3. By fitting the experimental data, apparent activation energy for the mechanochemical reaction was calculated as 39.6 kJ/mol.

Published
2019

21. Novel core–shell structured MgH2/AlH3@CNT nanocomposites with extremely high dehydriding–rehydriding properties derived from nanoconfinement.

Author

Duan, Congwen, Wu, Mengmeng, Cao, Yizheng, Fu, Dong, Zhang, Yuling, Su, Zhaohua, Sun, Zhize, and Wu, Ying

Abstract

In this work, a simple and efficient nanoconfinement method is developed to construct a novel "core–shell" structured MgH2/AlH3@CNT nanocomposite (MgH2/AlH3@CNTs). CNTs with a high specific surface area (550 m2 g−1) and a small diameter (approximately 6–8 nm) contribute to finer crystal size (60–80 nm) of the core–shell structured MgH2/AlH3@CNT nanoparticles. Owing to the special "core–shell" structure, this nanocomposite shows significantly better H2 de- and absorption thermodynamics and kinetics. The composite releases H2 at ∼71 °C, which is substantially below the temperatures observed for the MgH2, nano-AlH3, and other MgH2/AlH3 composites. It also shows dramatically improved dehydriding and rehydriding kinetics, rapidly releasing 8.20 wt% H2 in 1 h at 200 °C and taking up 5.61 wt% H2 in 0.16 h at 250 °C. During dehydrogenation and rehydrogenation, the CNTs can effectively prevent the aggregation of the nanocomposite particles and enhance the MgH2 and AlH3 direct contact. Thus, the application of these noteworthy core–shell MgH2/AlH3@CNTs offers a very promising way to improve the kinetics of the nanoconfinement system. [ABSTRACT FROM AUTHOR]

Published
2021
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24. Effect of Zn and Zr addition on the synthesis of an AlH3/MgCl2 nanocomposite and its de-hydriding properties

Author

Duan Congwen, Sun Yu, and Hu Lianxi

Subjects
Nanocomposite, Materials science, Chemical engineering, Transition metal, General Chemical Engineering, Metallurgy, General Chemistry, Hydrogen desorption, Grain size
Abstract

This paper presents the preliminary findings of the effects of 3d transition metals on the synthesis of an AlH3/MgCl2 nanocomposite and its de-hydriding properties. The average grain size of as-milled AlH3 is 4–6 nm with a desirable hydrogen desorption content of 9.69 wt%, indicating that AlH3 is a promising hydrogen-storage material.

Published
2015

30. An insight into the process and mechanism of a mechanically activated reaction for synthesizing AlH3 nano-composites.

Author

Duan, Congwen, Hu, Lianxi, Sun, Yu, Zhou, Haiping, and Yu, Huan

Subjects
*NANOCOMPOSITE materials, *NUCLEAR magnetic resonance, *ALUMINUM hydride, *HYDRIDES, *HYDROGEN storage
Abstract

The reaction pathway as well as the mechanism of the solid state reaction between MgH2 and AlCl3 has been a mystery so far. Based on SEM, TEM and NMR (Nuclear Magnetic Resonance) analyses, an amorphous intermediate (AlH6)n was preferentially formed and recrystallized as a γ phase at the final stage of the reaction. As a novel finding, this research provides a deep insight into the process and mechanism of this mechanically activated reaction. [ABSTRACT FROM AUTHOR]

Published
2015
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31. Inexpensive and eco-friendly nanostructured birnessite-type δ-MnO2: A design strategy from oxygen defect engineering and K+pre-intercalation

Author

Lv, Wei, Meng, Jingwen, Li, Yiming, Yang, Weijie, Tian, Yonglan, Lyu, Xuefeng, Duan, Congwen, Ma, Xiaolei, and Wu, Ying

Abstract

Nanostructured birnessite-type δ-MnO2(KMO-V) with intercalated K+and oxygen vacancies is synthesized by a hydrothermal method at 160 °C followed by annealing under 300 °C in Ar atmosphere with non-toxic and inexpensive γ-MnO2(Unit price: 0.96–1.6 US$ Kg−1) as raw material. The interplanar spacing in (001) diffraction direction of KMO-V is near 0.719 nm. The considerable initial discharge potential of about 1.8 V, specific energy of 389.88 Wh kg−1, and cyclic stability of 91.9% after 1500 cycles at 1.0 A g−1of KMO-V are obtained. A hybrid intercalation mechanism of H+and Zn2+is revealed, KMO-V has the best diffusion kinetics performance of Zn2+among the samples according to the calculation based on density functional theory (DFT). The by-product Zn4(OH)6SO4·4H2O and Mn2+are thought to be the primary factors of capacity decay, the synergy of K+pre-intercalation and oxygen vacancies plays a critical role of enhancing structural stability and reaction kinetics in KMO-V. Thus, this work provides an eco-friendly research method of inexpensive electrode material in aqueous Zn-ion batteries (AZIBs) for large-scale energy storage.

Published
2022
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