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Cyclotriphosphazene (P3N3) hybrid framework for aggregation induced photocatalytic hydrogen evolution and degradation of rhodamine B

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MATERIALS CHEMISTRY FRONTIERS 2020年第11期4卷 3216-3225页

作者： Basharat, Majid Khan, Muhammad Shuaib Abbas, Yasir Zhang, Shuangkun Ma, Hanlin Wu, Zhanpeng Liu, Wei Beijing Univ Chem Technol Minist Educ Key Lab Carbon Fiber & Funct Polymers Beijing 100029 Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn MPEE 28 West Xianning Rd Xian 710049 Peoples R China Beijing Univ Chem Technol Coll Mat Sci & Engn Beijing 100029 Peoples R China

The utilization of solar energy is an epitome towards water splitting for hydrogen generation and environmental remediation. For efficient use of solar energy, photocatalysts capable of light-harvesting, with appropriate band energetics, that are inexpensive, stable, and scalable, are desired. Herein, a prototypical cyclotriphosphazene (P3N3)-based covalent inorganic-organic hybrid framework (CIOF) is designed with highly crosslinked aggregation that can produce hydrogen fuel from photocatalytic water splitting, as well as the degradation of industrial waste-water pollutant (rhodamine B). The P3N3-CIOF was synthesized by the aggregation, self-assembly, and subsequent polycondensation of hexachlorocyclotriphosphazene, tris(4-hydroxyphenyl)ethane and pyridine, in one-pot under ultrasonication. Morphology and structure of the newly synthesized P3N3-CIOF are characterized through scanning electron microscopy, Fourier transform infrared spectroscopy, solid-state P-31 and C-13 nuclear magnetic resonance spectroscopy, X-ray photoelectron microscopy, UV-visible absorbance, photoluminescence, and micro-spectrophotometry. The P3N3-CIOF shows selective response to the UV-visible light by emitting bright green (Ex. 365 nm), yellow (Ex. 420 nm), and red (Ex. 546 nm) colors. Moreover, the onset bandgap (2.14 eV) and the potential of the conduction band (-0.26 eV) and valence band (+1.88 eV) straddle the potential range for photocatalytic water splitting and dye degradation. The as-synthesized P3N3-CIOF continuously produced hydrogen fuel (24.5 mu mol g(-1) h(-1)) during photocatalytic water splitting for a period of 16 h, using Pt (3 wt%) and triethanolamine as the co-catalyst and holes scavenger, respectively. It also showed photodegradation ability to rhodamine B as a proxy dye to industrial waste-water pollutants. The plausible photocatalytic mechanism is also proposed based on the energetics of the photogenerated excitons, and scavenging experiments. These findings exemplify

关键词： Fourier transform infrared spectroscopy

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Overall and local effects of operating parameters on water management and performance of open-cathode PEM fuel cells

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APPLIED ENERGY 2022年 315卷 118978-118978页

作者： Yang, Yupeng Jia, Haijuan Liu, Zhi Bai, Nan Zhang, Xiaolai Cao, Tong Zhang, Jie Zhao, Pengbing He, Xiaocong Xidian Univ Key Lab Elect Equipment Struct Design Minist Educ Xian 710071 Shaanxi Peoples R China Xi An Jiao Tong Univ Int Res Ctr Renewable Energy State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Tianjin Univ State Key Lab Engines 135 Yaguan Rd Tianjin 300350 Peoples R China Xi An Jiao Tong Univ Sch Life Sci & Technol Key Lab Biomed Informat Engn Minist Educ Xian 710049 Peoples R China Xi An Jiao Tong Univ Bioinspired Engn & Biomech Ctr BEBC Xian 710049 Peoples R China

Water management in open-cathode PEM fuel cells is challenging due to direct supply of ambient air. In this contribution, the water transport mechanisms and local water distributions in open-cathode PEM fuel cells are studied using local current measurement and various electrochemical methods. The results show local membrane dehydration occurs and the water distribution is much uneven when current density is lower than 200 mA cm(-2). As operating current increases, the water content of membrane increases rapidly until the membrane is fully hydrated and the local water distribution also becomes more uniform. Whereas, liquid water begins to accumulate in gas diffusion layer and catalyst layer when the current density is over 700 mA cm(-2). Furthermore, the effects of operating conditions are investigated. On the one hand, when the current density is lower than 500 mA cm(-2), improving temperature and air velocity can reduce cell performance as too much water is removed out of fuel cell, leading to membrane dehydration. On the other hand, when the current density is above 600 mA cm(-2), increasing cell temperature and air velocity can improve cell performance by removing excessive water in pores of gas diffusion layer and catalyst layer. The experimental fuel cell achieves the best performance with the temperature of 45celcius and air velocity of 2.2 m/s.

关键词： PEM fuel cell Open-cathode Water management Local current distribution Cell performance

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Large eddy simulation on the respective roles of integral length scale and turbulence intensity on turbulent premixed combustion 12

Large eddy simulation on the respective roles of integral le...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Shilong, Guo Meng, Zhang Jinhua, Wang Xutao, Wei Zuohua, Huang State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

The effects of integral length scale () and turbulence intensity (? ) on premixed combustion are studied using large eddy simulation. Three groups of lean CH4/air flames are carried out using the thickened flame model combined with a two-step reduced chemical mechanism. Two groups vary at constant ? and the other group increases ? from low to high while keeping unchanged. One of the cases is validated to available experimental data, showing good agreement for the flame-brush structure. The numerical results show that the increase in or ? leads to a decrease in flame-brush height and an increase in flame-brush thickness and volume. The turbulent flame speed () will be enhanced by these two factors within the scope of our study. All the flame-brush structure data, including height, thickness, volume and area, and also collapse onto a single line when the turbulent Reynolds number is used as abscissa. The probability density function distributions of filtered thickened flame front curvature show that will be increased by and ? through increasing the amount of large-scale and small-scale wrinkling structures respectively. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Large eddy simulation

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A review of key components of hydrogen recirculation subsystem for fuel cell vehicles

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ENERGY CONVERSION AND MANAGEMENT-X 2022年 15卷

作者： Han, Jiquan Feng, Jianmei Chen, Ping Liu, Yunmei Peng, Xueyuan Xi An Jiao Tong Univ Sch Energy & Power Engn Xian 710049 Shaanxi Peoples R China Ningbo Green Power Hydrogen Technol Res Inst Co Lt Ningbo 315033 Zhejiang Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Shaanxi Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn 28 Xianning West Rd Xian 710049 Peoples R China

Hydrogen energy and fuel cell technology are critical clean energy roads to pursue carbon neutrality. The proton exchange membrane fuel cell (PEMFC) has a wide range of commercial application prospects due to its simple structure, easy portability, and quick start-up. However, the cost and durability of the PEMFC system are the main barriers to commercial applications of fuel cell vehicles. In this paper, the core hydrogen recirculation components of fuel cell vehicles, including mechanical hydrogen pumps, ejectors, and gas-water separators, are reviewed in order to understand the problems and challenges in the simulation, design, and application of these components. The types and working characteristics of mechanical pumps used in PEMFC systems are summarized. Furthermore, corresponding design suggestions are given based on the analysis of the design challenges of the mechanical hydrogen pump. The research on structural design and optimization of ejectors for adapting wide power ranges of PEMFC systems is analyzed. The design principle and difficulty of the gas-water separator are summarized, and its application in the system is discussed. In final, the integration and control of hydrogen recirculation components controlled cooperatively to ensure the stable pressure and hydrogen supply of the fuel cell under dynamic loads are reviewed.

关键词： Hydrogen recirculation Fuel cell Hydrogen pump Ejector Separator

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Thermal-hydraulic characteristic of short-length self-rotating twisted tapes in a circular tube

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INTERNATIONAL COMMUNICATIONS IN HEAT AND MASS TRANSFER 2021年 122卷 105157-105157页

作者： Zhang, Shaojie Lu, Lin Wang, Qiuwang Hong Kong Polytech Univ Dept Bldg Serv Engn Hung Hom Kowloon 11 Yuk Choi Rd Hong Kong Peoples R China Xi An Jiao Tong Univ Sch Energy & Power Engn State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

This study investigated the thermal-hydraulic characteristic of a circular tube equipped with self-rotating twisted tapes (SRTTs) at different length ratios (LR = 0.3, 0.45, 0.6, and 1) when the Reynolds number is in the range of 12,000 to 45,000. The experimental outcomes revealed that full-length SRTTs can start rotating at a lower Reynolds number (Re = 18,700), and larger length ratios significantly increase the rotational speed. Moreover, the tube equipped with full-length SRTTs was found to provide a higher friction factor, thermal performance factor and Nussle number compared with those with shorter length ratios. The thermal performance factor was considerably increased from 0.91 to 0.95, 0.95 to 1.05, 1.04 to 1.08, and 1.09 to 1.27 owing to the operating condition of SRTTs switching from a stationary to a rotating condition. Finally, this study also derived associated correlations regarding the length ratio to predict the thermal performance in formulas of the Nussle number and friction factor.

关键词： Thermal-hydraulic characteristic Length ratio Short-length self-rotating twisted tapes Thermal performance factor

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Theoretical Chemical Kinetic Study of the H-atom Abstraction from Ethanol by Hydroperoxyl Radical 12

Theoretical Chemical Kinetic Study of the H-atom Abstraction...

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12th Asia-Pacific Conference on Combustion, ASPACC 2019

作者： Zhao, Qian Sun, Wuchuan Deng, Fuquan Yang, Feiyu Zhang, Yingjia Huang, Zuohua State Key Laboratory of Multiphase Flow in Power Engineering Xi'an Jiaotong University Xi'an710049 China

Reactions of ethanol + hydroperoxyl radical (H?2) are well known a crucial reaction class in oxidation mechanism of ethanol. However, the kinetic parameters of the reactions are basically extrapolated by analogy with n-butanol + H?2 system calculated by Zhou et al. [1]. The reliability of such the analogy remains to be seen, as no directly theoretical or experimental evidence is available in literature to date. In this study, thermal rate coefficients of H-atom abstraction reactions for ethanol + H?2 system were calculated at both CCSD(T)/cc-pVTZ//M06-2x/def-TZVP and CCSD(T)/CBS//M06-2x/def-TZVP levels of theory, with an uncertainty of a factor of 3, by means of using both conventional transition-state theory and canonical variational transition-state theory. Similar to n-butanol + H?2 system, the title reactions are dominated by alpha site H-abstraction, whereas the rate coefficients of all channels of ethanol are slightly slower than that of n-butanol + H?2 system. Generally, the new calculations show only limited effect on ethanol reactivity at low pressures and high temperatures (over 1300 K) but it prevents the kinetic mechanisms to over-predict ignition delay times under engine relevant conditions. © Asia-Pacific Conference on Combustion, ASPACC *** right reserved.

关键词： Ethanol

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Research on control strategies for rapid load decrease events in fluoride salt reactor-supercritical CO2 Brayton cycle systems

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Nuclear engineering and Design 2025年 439卷

作者： Shichang, Yun Xinyu, Li Dalin, Zhang Ping, Song Wenxi, Tian Suizheng, Qiu Guanghui, Su State Key Laboratory of Multiphase Flow in Power Engineering Shaanxi Key Laboratory of Advanced Nuclear Energy and Technology School of Nuclear Science and Technology Xi'an Jiaotong University Xi'an710049 China State Key Laboratory of Marine Thermal Power Technology Wuhan Second Ship Design and Research Institute Wuhan China

This study delves into the control strategies for the Fluoride-salt-cooled High-temperature Reactor-Supercritical CO2 (SCO2) Brayton cycle power generation system under rapid grid load reduction scenarios. By developing a dynamic simulation model, the system's dynamic response characteristics under rapid load changes were analyzed, and a combined control strategy emphasizing safety, speed, and economic efficiency was proposed. The research first compared the dynamic response characteristics and steady-state performance of different bypass configurations under load rejection conditions. The computational results indicate that all three bypass control systems exhibit excellent load-following capabilities, effectively responding to a 50 % load step change within 10 s. However, significant differences were observed in their steady-state thermodynamic performance: the upper cycle bypass control achieves the highest steady-state efficiency (η = 29.92 %), followed by the turbine bypass control (η = 27.50 %), with the heat source bypass control showing relatively lower efficiency (η = 26.49 %). Although the upper cycle bypass offers superior efficiency, it leads to a substantial increase in the working fluid flow through the compressor (ΔQ = 15 %) during operation, raising the risk of compressor blockage and necessitating additional flow restriction and anti-blocking interlock control systems. Considering system safety, control complexity, and engineering feasibility, the turbine bypass system, with its relative independence and lower operational risk, is deemed more suitable as the primary control strategy for load rejection conditions. Building on this, the study proposes a combined control strategy that leverages the strengths of both bypass control and inventory control. During the initial phase of rapid load reduction, the bypass control system quickly adjusts the turbine bypass valve opening to promptly respond to grid load changes, ensuring system frequency stability

关键词： Frequency stability

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Direct numerical simulation of flow and heat transfer in bidisperse gas-solid systems

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CHEMICAL engineering SCIENCE 2021年 239卷 116645-116645页

作者： Huang, Zheqing Wang, Lingxue Li, Yu Zhou, Qiang Xi An Jiao Tong Univ Sch Chem Engn & Technol Xian Peoples R China Xi An Jiao Tong Univ Shaanxi Key Lab Energy Chem Proc Intensificat Xian Peoples R China Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian 710049 Peoples R China

The flow and heat transfer in bidisperse gas-solid systems with particle diameter ratio ranging from 1:2 to 1:4 have been numerically investigated via an immersed boundary-lattice Boltzmann method. The modeling for the overall Nusselt number (Nu) is pursued. The results show that the overall Nu obtained from the simulation results can be predicted well using the monodisperse correlations by defining an appropriate equivalent diameter. An accurate model to predict Nu for each species is formulated through a correction to the monodisperse heat transfer correlations. Since the relative solid volume fraction ratio of large-to-small spheres has marginal influence on Nu for each species, the correction term is only closed as a function of the total solid volume fraction and scaled particle diameter. The predictability of the model is evaluated. The results demonstrate that the model can give more accurate estimations for Nu of each species. (c) 2021 Elsevier Ltd. All rights reserved.

关键词： Bidisperse Gas-solid systems Heat transfer Immersed boundary-lattice Boltzmann method Nusselt number

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MgO and Au nanoparticle Co-modified g-C_(3)N_(4)photocatalysts for enhanced photoreduction of CO_(2)with H_(2)O

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Chinese Journal of Catalysis 2021年第5期42卷 781-794页

作者： Naixu Li Meiyou Huang Jiancheng Zhou Maochang Liu Dengwei Jing School of Chemistry and Chemical Engineering Southeast UniversityNanjing 211189JiangsuChina International Research Center for Renewable Energy State Key Laboratory of Multiphase Flow in Power EngineeringXi’an Jiaotong UniversityXi’an 710049ShaanxiChina Jiangsu Key Laboratory for Biomass Energy and Material Institute of Chemical Industry of Forest ProductsChinese Academy of ForestryNanjing 210042JiangsuChina Suzhou Academy of Xi’an Jiaotong University Suzhou 215123JiangsuChina

The photoreduction of CO_(2)to achieve high-value-added hydrocarbons under simulated sunlight irradiation is advantageous,but *** this study,a series of MgO and Au nanoparticle-co-modified g-C_(3)N_(4)photocatalysts were synthesized and subsequently applied for the photocatalytic reduction of CO_(2)with H2O under simulated solar *** best photocatalytic performance was demonstrated by the Au and 3%MgO-co-modified g-C_(3)N_(4)photocatalysts with CO,CH_(4),CH3OH,and CH3CHO yields of 423.9,83.2,47.2,and 130.4μmol/g,respectively,in a 3-h *** investigated the effects of MgO and Au as cocatalysts on photocatalytic behaviors,*** characterizations and experimental results showed that the enhanced photocatalytic activity was due to the synergistic effect among the components of the ternary *** cocatalyst MgO can activate CO_(2)(adsorbed at the interface between the MgO and Au particles),and the Mg-N bonds formed in the MgO-CN nanosheets played an important role in the charge ***,the Au particles that were modified into MgO/g-C_(3)N_(4)can increase the absorption of visible light via the surface plasmon resonance effect and further reduce the activation energies of the photoreduction of CO_(2)using *** study provided an effective method for the modification of traditional primary photocatalysts with promising performance for photocatalytic CO_(2)reduction.

关键词： CO2 photoreduction MgO Au g-C3N4 Photocatalysis Synergistic effect Cocatalyst

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Enhanced removal of antimony in dyeing wastewater by mixing Fe3O4with manganese sand filter material

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WATER ENVIRONMENT RESEARCH 2020年第8期92卷 1208-1213页

作者： Liu, Hongbo Ying, Qiyan Li, Congyu Norra, Stefan Lichtfouse, Eric Univ Shanghai Sci & Technol Sch Environm & Architecture Shanghai Peoples R China Karlsruhe Inst Technol Inst Mineral & Geochem Karlsruhe Germany Aix Marseille Univ Coll France CEREGE INRACNRSIRD Aix En Provence France Xi An Jiao Tong Univ State Key Lab Multiphase Flow Power Engn Xian Peoples R China

Wastewaters from the printing and dyeing industries contain many contaminants in particular antimony (Sb) that end up in the environment. Both manganese sand filter and Fe(3)O(4)have good removal effect on Sb, and are cheap and easy to obtain. We made a filter material by mechanically mixing the manganese sand filter material and ferro-ferric oxide (Fe3O4). The Fe-Mn oxide filter material was analyzed by X-ray diffraction. We studied the filtration of real wastewater from a dyeing wastewater resource recovery facility in Suzhou, China, containing Sb at high concentration of 410 mu g/L, using dynamic tests in adsorption columns during 7 days. We tested the effects of filter material volume filling ratio, the empty bed contact time (EBCT), pH, and back washing on the removal of Sb. Results show that the addition of Fe(3)O(4)enhanced the removal of Sb, reaching 85% of initial Sb. When the initial influent pH of the raw water is 3.0, the volume filling ratio of filter material is 60%, the EBCT is 20 min, and the developed dynamic Fe-Mn oxide filter has the best removal effect on Sb. Daily back washing of the filter keeps a Sb removal rate of about 80%. Practitioner points A novel and cheap Fe-Mn oxide was developed for Sb removal from dyeing wastewater. A self-designed filter device was designed to verify performance of the low-cost material. Optimal design and operational parameters of the filtration process were determined.

关键词： antimony removal dyeing wastewater dynamic filter heavy metal iron and manganese mixture

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