共查询到20条相似文献，搜索用时 15 毫秒
1.
Lingtao Kong Zhouxun Li Hui Zhang Mengmeng Zhang Jiaxing Zhu Mingli Deng Zhenxia Chen Yun Ling Yaming Zhou 《Frontiers of Chemical Science and Engineering》2022,16(7):1114
Improvement of the low-cost transition metal electrocatalyst used in sluggish oxygen evolution reaction is a significant but challenging problem. In this study, ultrafine Fe-modulated Ni nanoparticles embedded in a porous Ni-doped carbon matrix were produced by the pyrolysis of zirconium metal–organic–frameworks, in which 2,2′-bipyridine-5,5′-dicarboxylate operating as a ligand can coordinate with Ni2+ and Fe3+. This strategy allows formation of Fe-modulated Ni nanoparticles with a uniform dimension of about 2 nm which can be ascribed to the spatial blocking effect of ZrO2. This unique catalyst displays an efficient oxygen evolution reaction electrocatalytic activity with a low overpotential of 372 mV at 10 mA·cm–2 and a small Tafel slope of 84.4 mV·dec–1 in alkaline media. More importantly, it shows superior durability and structural stability after 43 h in a chronoamperometry test. Meanwhile, it shows excellent cycling stability during 4000 cyclic voltammetry cycles. This research offers a new insight into the construction of uniform nanoscale transition metals and their alloys as highly efficient and durable electrocatalysts. 相似文献
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Xinyi Yang Xiaolu Liu Yanfang Liu Xiao-Feng Wang Zhongshan Chen Xiangke Wang 《Frontiers of Chemical Science and Engineering》2023,17(4):395
Radioactive iodine exhibits medical values in radiology, but its excessive emissions can cause environmental pollution. Thus, the capture of radioiodine poses significant engineering for the environment and medical radiology. The adsorptive capture of radioactive iodine by metal–organic frameworks (MOFs) has risen to prominence. In this work, a Th-based MOF (denoted as Th-BPYDC) was structurally designed and synthesized, consisting of [Th6(μ3-O)4(μ3-OH)4(H2O)6]12+ clusters, abundant bipyridine units, and large cavities that allowed guest molecules diffusion and transmission. Th-BPYDC exhibited the uptake capacities of 2.23 g·g−1 and 312.18 mg·g−1 towards I2 vapor and I2 dissolved in cyclohexane, respectively, surpassing its corresponding analogue Th-UiO-67. The bipyridine units boosted the adsorption performance, and Th-BPYDC showed good reusability with high stability. Our work thus opened a new way for the synthesis of MOFs to capture radioactive iodine. 相似文献
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Xiyuan Bu Ming Tian Hongqing Wang Lin Wang Liyong Yuan Weiqun Shi 《Frontiers of Chemical Science and Engineering》2022,16(11):1632
Although metal–organic frameworks offer a new platform for developing versatile sorption materials, yet coordinating the functionality, structure and component of these materials remains a great challenge. It depends on a comprehensive knowledge of a “real sorption mechanism”. Herein, a ternary mechanism for U(VI) uptake in metal–organic frameworks was reported. Analogous MIL-100s (Al, Fe, Cr) were prepared and studied for their ability to sequestrate U(VI) from aqueous solutions. As a result, MIL-100(Al) performed the best among the tested materials, and MIL-100(Cr) performed the worst. The nuclear magnetic resonance technique combined with energy-dispersive X-ray spectroscopy and zeta potential measurement reveal that U(VI) uptake in the three metal–organic frameworks involves different mechanisms. Specifically, hydrated uranyl ions form outer-sphere complexes in the surface of MIL-100s (Al, Fe) by exchanging with hydrogen ions of terminal hydroxyl groups (Al-OH2, Fe-OH2), and/or, hydrated uranyl ions are bound directly to Al(III) center in MIL-100(Al) through a strong inner-sphere coordination. For MIL-100(Cr), however, the U(VI) uptake is attributed to electrostatic attraction. Besides, the sorption mechanism is also pH and ionic strength dependent. The present study suggests that changing metal center of metal–organic frameworks and sorption conditions alters sorption mechanism, which helps to construct effective metal–organic frameworks-based sorbents for water purification. 相似文献
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Xin Chen Liang Luo Shihong Huang Xingbo Ge Xiuyun Zhao 《Frontiers of Chemical Science and Engineering》2023,17(5):570
Recently, metal–organic frameworks are one of the potential catalytic materials for electrocatalytic applications. The oxygen reduction reaction and oxygen evolution reaction catalytic activities of heterometallic cluster-based organic frameworks are investigated using density functional theory. Firstly, the catalytic activities of heterometallic clusters are investigated. Among all heterometallic clusters, Fe2Mn–Mn has a minimum overpotential of 0.35 V for oxygen reduction reaction, and Fe2Co–Co possesses the smallest overpotential of 0.32 V for oxygen evolution reaction, respectively 100 and 50 mV lower than those of Pt(111) and RuO2(110) catalysts. The analysis of the potential gap of Fe2M clusters indicates that Fe2Mn, Fe2Co, and Fe2Ni clusters possess good bifunctional catalytic activity. Additionally, the catalytic activity of Fe2Mn and Fe2Co connected through 3,3′,5,5′-azobenzenetetracarboxylate linker to form Fe2M–PCN–Fe2M is explored. Compared with Fe2Mn–PCN–Fe2Mn, Fe2Co–PCN–Fe2Co, and isolated Fe2M clusters, the mixed-metal Fe2Co–PCN–Fe2Mn possesses excellent bifunctional catalytic activity, and the values of potential gap on the Mn and Co sites of Fe2Co–PCN–Fe2Mn are 0.69 and 0.70 V, respectively. Furthermore, the analysis of the electron structure indicates that constructing a mixed-metal cluster can efficiently enhance the electronic properties of the catalyst. In conclusion, the mixed-metal cluster strategy provides a new approach to further design and synthesize high-efficiency bifunctional electrocatalysts. 相似文献
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Yan Xu Lu Wang Junwei Wu Guanzhong Zhai Daohua Sun 《Frontiers of Chemical Science and Engineering》2023,17(3):314
Acceptorless alcohol dehydrogenation stands out as one of the most promising strategies in hydrogen storage technologies. Among various catalytic systems for this reaction, cost-effective molecular catalysts using phosphine-free ligands have gained considerable attention. However, the central challenge for using non-precious metals is to overcome the propensity of reacting by one-electron pathway. Herein, we synthesized a phosphine-free η5-C5Me5-Co complex by using the metal–ligand cooperative strategy and compared its activity with analogous catalysts toward acceptorless alcohol dehydrogenation. The catalyst showed excellent performance with a turnover number of 130.4 and a selectivity close to 100%. The improved performance among the class of η5-C5Me5-Co complexes could be attributed to the more accessible Co center and its cooperation with the redox-active ligand. To further study the systematic structure-activity relationship, we investigated the electronic structures of η5-C5Me5-Co complexes by a set of characterizations. The results showed that the redox-active ligand has a significant influence on the η5-C5Me5-Co moiety. In the meantime, the proximal O−/OH group is beneficial for shuttling protons. For the catalytic cycle, two dehydrogenation scenarios were interrogated through density functional theory, and the result suggested that the outer-sphere pathway was preferred. The formation of a dihydrogen complex was the rate-determining step with a ΔG value of 16.9 kcal∙mol‒1. The electron population demonstrated that the η5-C5Me5 ligand played a key role in stabilizing transition states during dehydrogenation steps. This work identified the roles of vital ligand components to boost catalytic performance and offered rationales for designing metal–ligand cooperative nonprecious metal complexes. 相似文献
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Gudmund Smedler 《加拿大化工杂志》1989,67(1):51-61
The kinetics of the consecutive hydrogenation reactions 2-ethyl-hexenal → 2-ethyl-hexanal → 2-ethyl-hexanol were studied in the liquid phase in presence of commercial Ni, Pd and Ni-S catalysts. The Pd and Ni-S catalysts were extremely selective with respect to the formation of 2-ethyl-hexanal, while the full reaction sequence was readily catalyzed by nickel. A Langmuir-Hinshelwood model with dissociative hydrogen adsorption was found to be the most probable model, for all three catalysts. The proposal of dissociative hydrogen adsorption of the Ni-S catalyst was supported by an independent gas-phase experiment, using the H2/D2 exchange reaction as a model reaction for the hydrogen àdsorption process. 相似文献
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使用冷等离子体表面改性技术在石墨烯表面引入适量含氮基团,通过优化等离子体气源、等离子体放电功率、放电时间和工作气压等工艺条件,高效制备具有两亲表面的氮掺杂石墨烯(NDGR)。采用傅里叶变换红外光谱(FT-IR)、拉曼光谱仪(Raman)、有机元素分析(OEA)、透射电子显微镜(TEM)和水接触角(WCA)等方法对其进行表征。接着以NDGR为载体,制备铂纳米催化剂Pt/NDGR,用于肉桂醛和巴豆醛水相加氢反应。结果表明,采用等离子体两步接枝工艺,即先以氧气(O2)为等离子体气源活化石墨烯表面,再以氨(NH3)为等离子体气源在石墨烯表面接枝含氮基团得到的氮掺杂石墨烯NDGR(O2-NH3)具有最佳的表面性质。与原始石墨烯负载Pt催化剂(Pt/GR)相比,最佳条件 (放电功率140 W, 工作气压200 Pa,放电时间6 min) 下制备的NDGR(O2-NH3)负载Pt催化剂Pt/NDGR(O2-NH3)在肉桂醛(CAL)和巴豆醛(CRAL)水相加氢反应中显示出优良的催化性能。反应条件为80 ℃,3 MPa下,Pt/NDGR(O2-NH3)在4 h内催化肉桂醛的转化率达98%,对不饱和醇肉桂醇(COL)保持高选择性(约84%);而在巴豆醛水相加氢反应中,Pt/NDGR(O-NH)的表观速率常数kapp达0.53 h-1,远高于Pt/GR (0.37 h-1)。接近完全反应时,Pt/NDGR(O-NH3)亦对巴豆醇(CROL)保持了高选择性(约40%)。Pt/NPGR(O2-NH3)的高催化性能得益于石墨烯表面接枝少量含氮基团后表面性质的增强,包括Pt纳米粒子锚定位点的增加、对底物的高吸附性能以及金属-载体间协同作用。 相似文献
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Haonan Shi Xiaoyu Gu Yinteng Shi Dandan Wang Sihao Shu Zhongze Wang Jixiang Chen 《Frontiers of Chemical Science and Engineering》2023,17(2):139
Porous carbon-encapsulated Ni and Ni–Sn intermetallic compound catalysts were prepared by the one-pot extended Stöber method followed by carbonization and tested for in-situ hydrothermal deoxygenation of methyl palmitate with methanol as the hydrogen donor. During the catalyst preparation, Sn doping reduces the size of carbon spheres, and the formation of Ni–Sn intermetallic compounds restrain the graphitization, contributing to larger pore volume and pore diameter. Consequently, a more facile mass transfer occurs in carbon-encapsulated Ni–Sn intermetallic compound catalysts than in carbon-encapsulated Ni catalysts. During the in-situ hydrothermal deoxygenation, the synergism between Ni and Sn favors palmitic acid hydrogenation to a highly reactive hexadecanal that easily either decarbonylate to n-pentadecane or is hydrogenated to hexadecanol. At high reaction temperature, hexadecanol undergoes dehydrogenation–decarbonylation, generating n-pentadecane. Also, the C–C bond hydrolysis and methanation are suppressed on Ni–Sn intermetallic compounds, favorable for increasing the carbon yield and reducing the H2 consumption. The n-pentadecane and n-hexadecane yields reached 88.1% and 92.8% on carbon-encapsulated Ni3Sn2 intermetallic compound at 330 °C. After washing and H2 reduction, the carbon-encapsulated Ni3Sn2 intermetallic compound remains stable during three recycling cycles. This is ascribed to the carbon confinement that effectively suppresses the sintering and loss of metal particles under harsh hydrothermal conditions. 相似文献
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以硼氢化钠为还原剂,聚乙烯亚胺(PEI)为稳定剂,制备了表面带正电的PEI-保护的金纳米粒子,以此为金源,采用模板法制备微米级SiO2/Au/γ-Fe2O3金磁复合微球,球形完整、分散良好,无金泄露现象。将SiO2/Au/γ-Fe2O3金磁复合微球用于催化对硝基苯胺、对氯硝基苯还原反应,显示出高催化活性及选择性。 相似文献
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分别以ZrO2、SiO2及ZrO2-SiO2复合氧化物为载体,采用等体积浸渍法制备了Ni含量为10%（质量分数）的催化剂,考察了其催化乙酰丙酸液相加氢性能。采用N2-物理吸附、NH3-TPD、H2-TPR、XRD、TEM等表征手段对催化剂进行了表征。研究结果表明,在所制备的催化剂上,乙酰丙酸先经C=O加氢生成4-羟基戊酸,后者快速脱水酯化为γ-戊内酯。Ni/ZrO2-SiO2催化剂较Ni/ZrO2与Ni/SiO2催化剂具有高的金属分散度和丰富的表面酸性中心,表现出高的C=O加氢活性以及优异的乙酰丙酸加氢合成γ-戊内酯性能。在反应温度为200℃,氢气压力4 MPa的反应条件下,乙酰丙酸的转化率达到100%,γ-戊内酯的选择性大于99.9%。 相似文献
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钢铁常温发黑工艺及其生产应用 总被引：3，自引：0，他引：3
介绍钢铁常温发黑工艺及其大批量生产要点,讨论了常温发黑工艺的成膜机理。与传统碱性高温发黑工艺比较,常温发黑工艺总成本下降20％—30％。 相似文献
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In order to detect possible effects of deposited carbonaceous layers on the hydrogenation of acetylene, a pulse flow reactor was used to study this reaction. Silica supported Ni and Ir catalysts were used to study the effect of variations in the particle size and of combining the active metal with an inactive component (Au). 相似文献
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Our studies on the effect of metal compositions on the catalytic activity of the rhodium‐based bimetallic nanocatalysts revealed that the nanoparticles with a 4:1 ratio of rhodium to cobalt, were more active than the rhodium monometallic nanoparticles in the selective hydrogenation of unsaturated carbon‐carbon bonds with hydrous hydrazine as a hydrogen source. The nanocatalysts effected this hydrogenation process in good‐to‐excellent yields with high functional group tolerance, and could be reused 10 times without the loss of catalytic activity. The catalyst characterization by X‐ray photoelectron spectroscopy, transmission electron microscopy and line‐scanning analysis suggested that the coexistence of metallic rhodium and cobalt plays an important role in the enhancement of catalytic activity. 相似文献
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以多壁碳纳米管和椰壳活性炭为载体,分别采用溶胶固载法和等体积浸渍法制备负载型纳米金催化剂。采用N_2吸附-脱附、XRD、TEM和XPS等对碳载体和纳米金催化剂样品进行表征,并研究纳米金催化剂在肉桂醛选择性加氢反应中的催化性能。结果表明,HNO_3-H_2SO_4预处理可以增加碳载体表面的含氧基团和含氮基团,在肉桂醛加氢反应中,溶胶固载法得到的更小尺寸的纳米金催化剂对C=C双键加氢选择性高,等体积浸渍法制备的纳米金催化剂对C=O双键加氢选择性高,椰壳活性炭为载体催化剂的C=C加氢催化活性优于多壁碳纳米管。 相似文献
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氮杂化介孔碳是在有序介孔碳的骨架中掺入氮原子部分取代碳原子形成的多孔物质,是一种具有优异性价比的新型碳材料。综述了氮杂化介孔碳的各种制备方法及其特点,重点介绍了混合聚合物炭化法和共聚物炭化活化结合法等新型的氮杂化介孔碳的制备方法;介绍了制备氮杂化介孔碳的碳、氮原料的来源和特点;总结并提出了提高氮杂化介孔碳比电容的途径和方法;提出了导电性氮杂化介孔碳的制备新方法。建议将氮杂化介孔碳的制备和酚类废物处理结合起来,以实现酚类废物的综合利用;建议将掺氟氧化锡原位引入氮杂化介孔碳的制备中,催化活化得到导电性氮杂化介孔碳材料。 相似文献
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山梨醇用Raney 镍催化剂活化条件的研究 总被引：2，自引：0，他引：2
对葡萄糖加氢制山梨醇用Raney镍催化剂的活化条件进行了研究,用丙酮法测定催化剂的加氢活性,考察了活化时NaOH的用量、活化温度及活化时间对Raney 镍催化剂加氢活性的影响.实验结果表明,制备Raney镍催化剂较好的活化条件为:NaOH/Al(物质的量比)为4.5,活化温度50 ℃,活化时间为1.5 h. 相似文献