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排序方式: 共有1874条查询结果,搜索用时 19 毫秒
1.
《International Journal of Hydrogen Energy》2022,47(11):7432-7442
The durability of metal plate proton exchange membrane fuel cell (PEMFC) stack is still an important factor that hinders its large-scale commercial application. In this paper, we have conducted a 1000 h durability test on a 1 kW metal plate PEMFC stack, and explored the degradation of the core components. After 1000 h of dynamic load cycles, the voltage decay percentage of the stack under the current densities of 1000 mA cm?2 is 5.67%. By analyzing the scanning electron microscopy (SEM) images, the surfaces of the metal plates are contaminated locally by organic matter precipitated from the membrane electrode assembly (MEA). The SEM images of the catalyst coated membrane (CCM) cross section indicate that the MEA has undergone severe degradation, including the agglomeration of the catalyst layer, and the thinning and perforation of the PEM. These are the main factors that cause the rapid increase in hydrogen crossover flow rate and performance decay of the PEMFC stack. 相似文献
2.
《International Journal of Hydrogen Energy》2022,47(97):41111-41123
System durability is crucial for the successful commercialization of polymer electrolyte fuel cells (PEFCs) in fuel cell electric vehicles (FCEVs). Besides conventional electrochemical cycling durability during long-term operation, the effect of operation in cold climates must also be considered. Ice formation during start up in sub-zero conditions may result in damage to the electrocatalyst layer and the polymer electrolyte membrane (PEM). Here, we conduct accelerated cold start cycling tests on prototype fuel cell stacks intended for incorporation into commercial FCEVs. The effect of this on the stack performance is evaluated, the resulting mechanical damage is investigated, and degradation mechanisms are proposed. Overall, only a small voltage drop is observed after the durability tests, only minor damage occurs in the electrocatalyst layer, and no increase in gas crossover is observed. This indicates that these prototype fuel cell stacks successfully meet the cold start durability targets for automotive applications in FCEVs. 相似文献
3.
4.
《Ceramics International》2021,47(22):31485-31496
Mesoporous SmMnO3/CuMnOx catalyst was prepared by a two-step method using flaky CuMnOx with high specific surface and excellent catalytic ability as the carrier, which was further applied to photothermal synergistic degradation of gaseous toluene. Quantitative analysis of O2-TPD and H2-TPR showed that SmMnO3/CuMnOx exhibited abundant of the surface oxygen species and oxygen vacancies content, which enabled it to convert free oxygen to lattice oxygen more quickly during the reaction, and thus improving the reaction process. I-t and photoluminescence experiments demonstrated the improvement of photogenerated electron and hole separation ability of SmMnO3/CuMnOx catalyst. UV–Vis analysis manifested the full spectral range of absorption. XPS analysis verified the unequal positions of valence band of the two materials, which can facilitate the separation of photogenerated electrons from holes and improve the ability of better electron transfer. SmMnO3/CuMnOx catalyst has higher adsorbed oxygen content and light absorption capacity, which is beneficial to the catalytic oxidation. In situ DRIFTs proved that the oxidation reaction on the catalyst followed the Mars-van Krevelen redox cycle. The VOCs test found that SmMnO3/CuMnOx composite catalyst is with lower onset reaction temperature (T90 = 190 °C, T90, corresponding to 90% conversion) and good mineralization (100% at 275 °C). 相似文献
5.
Fenqi Du Dongmei Yang Yue Sun Yang Jiao Feng Teng Haibo Fan 《Ceramics International》2021,47(4):4963-4971
Ultrawide band gap semiconductor materials have attracted considerable attention in recent years owing to their great potential in the photocatalytic field. In this study, Zn-doped Ga2O3 nanofibers with various concentrations were synthesized via electrospinning; they exhibited a superior photocatalytic degradation performance of rhodamine B dye compared to that of undoped Ga2O3 nanofibers. The Zn dopant replaced Ga sites via replacement doping, which could increase the concentration of oxygen vacancies and lead to enhanced photocatalytic properties. When the Zn concentration increased, a Ga2O3/ZnGa2O4 hybrid structure formed, which could further enhance the photocatalytic performance. The separation of photogenerated carriers due to Zn doping and heterojunctions were the primary causes of the enhanced photocatalytic performance. This study provides experimental data for the fabrication of high-performance photocatalysts based on Ga2O3 nanomaterials. 相似文献
6.
Yunqi Li Jing Li Yang-Gang Wang Xiran Chen Mingtao Liu Zhong Zheng Xihong Peng 《International Journal of Hydrogen Energy》2021,46(24):13273-13282
In this work, density functional theory (DFT) calculations were used to investigate the mechanism of carbon corrosion on nitrogen-doped carbon support. Free energy diagrams were generated based on three proposed reaction pathways to evaluate corrosion mechanisms. The most energetically preferred mechanism on nitrogen-doped carbon was determined. The results show that the step of water dissociation to form #OH was the rate-determining step for gra-G-1N (graphene doped with graphitic N) and pyrr-G-1N (graphene doped with pyrrolic N). As for graphene doped with pyridinic N, the step of C#OC#O formation was critical. It was found that the control of nitrogen concentration was necessary for precisely designing optimized carbon materials. Abundance of nitrogen moieties aggravated the carbon corrosion. When the high potential was applied, specific types of graphitic N and pyridinic N were found to be favorable carbon modifications to improve carbon corrosion resistance. Moreover, the solvent effect was also investigated. The results provide theoretical insights and design guidelines to improve corrosion resistance in carbon support through material modification by inhibiting the adsorption of surface oxides (OH, O, and OOH). 相似文献
7.
Conjugated microporous polymer (CMP) is an emerging organic semiconductor with π-conjugated skele-tons,and the bandgap of CMP can be flexibly modulated to harvest visible light.Based on the diversity and adjustability of monomers in CMP,we designed and synthesized donor-accepter (D-A) type BTN-CMP through Sonogashira-Hagihara cross-coupling polymerization,further in-situ constructing series of inorganic/organic Z-scheme BW/BTN-n composite in the presence of Bi2WO6.After optimization,the tetracycline hydrochloride (Co =10 mg·L-1) degradation efficiency reached 84% with BW/BTN-2 as cata-lyst in 90 min under visible light irradiation,the apparent rate constant k1 is 0.017 min-1,which is 1.7 and 5.7 times higher than bare Bi2WO6 and BTN-CMP.X-ray photoelectron spectra and UV-Vis diffuse spectra showed that the enhanced photocatalytic activity originated from the tight heterojunction between Bi2WO6 and BTN-CMP,which can extend the light absorption range and facilitate the separation and transport of photogenerated charges in the interface of heterojunction.The active species trapping experiments and electron spin resonance technique revealed that h+ was the dominant active species during the photodegradation process of tetracycline hydrochloride (TCH).The present study demon-strated the feasibility to construct inorganic/organic composite for the photocatalytic degradation of environmental pollutants. 相似文献
8.
双金属复合氢氧化物(LDHs,又叫水滑石)因具有层状结构、稳定的物化性质和电子特性等优点,可以大范围地应用在污水处理中。目前,水滑石作为光催化剂及其复合材料在污水处理上的应用受到越来越多的关注。综述了水滑石光催化剂的制备及其改性,着重介绍了不同类型水滑石对水中不同污染物的去除效果,并简要阐述了水滑石光催化剂的作用机理和研究现状。最后,展望了水滑石光催化剂的发展趋势,以期为后续水滑石在污水处理上的应用提供借鉴。 相似文献
9.
目的 研究低温放电等离子体对黄曲霉毒素B1 (aflatoxin B1,AFB1)的降解效果及对巴旦木仁品质的影响。方法 以黄曲霉毒素B1为目标毒素,首先研究了低温放电等离子体在不同处理时间、不同电压和不同初始浓度下对目标毒素的降解效果,其次评估了低温放电等离子体处理对巴旦木仁中的理化指标及色差和香气成分的影响。结果 低温放电等离子体不同处理条件对AFB1的降解效果明显,以75 kV低温放电等离子体处理5 min,50 μg/mL的AFB1的降解率为95.03%。低温放电等离子体处理对巴旦木仁的理化性质、蛋白浓度、色差均未出现显著性差异(P>0.05),巴旦木仁的香气成分也得到了良好的保持。结论 低温放电等离子体对AFB1具有较明显的降解效果,且对巴旦木仁的品质无影响。这一研究有望为干果中真菌毒素的降解提供新思路,为保证干果的食品安全提供新途径。 相似文献
10.
金属化膜电容器是模块化多电平换流器(MMC)的关键设备,在长期工作电热应力作用下其状态不断劣化,给换流器和柔性直流输电系统的安全运行带来隐患。本文分别搭建了交、直流加速劣化试验平台,得到了不同电压作用形式和不同状态劣化程度的样品。进而利用共聚焦显微镜和扫描电子显微镜对解剖样品进行表面观测,结合能谱扫描的元素分析结果,掌握了金属化膜电容器在不同电压形式下的状态劣化特性。结果表明,电容器由于在不同电压下的劣化机理不同,电容值下降规律和劣化点形貌有明显不同;通过加速老化试验,得到了电容器在交、直流电压下劣化点的典型形貌特征,从而可以进一步分析金属化膜电容器劣化机理,具有实用价值。
关键词:金属化膜电容器; 劣化机理; 自愈; 电化学腐蚀
中图分类号:TM536 相似文献