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单原子催化剂的制备、表征及催化性能(英文) 被引量:19
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作者 王丽琼 黄亮 +3 位作者 梁峰 刘思敏 王玉华 张海军 《Chinese Journal of Catalysis》 CSCD 北大核心 2017年第9期1528-1539,共12页
单原子催化剂(SACs)是指金属以单原子形式均匀分散在载体上形成的具有优异催化性能的催化剂.与传统载体型催化剂相比,SACs具有活性高、选择性好及贵金属利用率高等优点,在氧化反应、加氢反应、水煤气变换、光催化制氢以及电化学催化等... 单原子催化剂(SACs)是指金属以单原子形式均匀分散在载体上形成的具有优异催化性能的催化剂.与传统载体型催化剂相比,SACs具有活性高、选择性好及贵金属利用率高等优点,在氧化反应、加氢反应、水煤气变换、光催化制氢以及电化学催化等领域都具有广泛应用,是目前催化领域的研究热点之一.常见的SACs制备方法有共沉淀法、浸渍法、置换反应法、原子层沉积法以及反奥斯瓦尔德熟化法等.实验及理论研究表明,单原子催化剂高的活性和选择性可归因于活性金属原子和载体之间的相互作用及由此引起的电子结构改变.载体是影响单原子催化剂性能的重要因素之一.目前常用的SACs载体有金属氧化物、二维材料和金属纳米团簇等,本文着重综述了这三种负载型SACs的制备、表征、催化性能及催化机理,并概述了SACs未来可能的发展方向和应用.研究表明,共沉淀法、湿浸渍法和反奥斯瓦尔德熟化法等方法可用来制备氧化物负载的SACs.高角环形暗场像-扫描透射电子显微镜(HAADF-STEM)表明金属是以单原子形式均匀分散在载体上,近边X射线吸收精细结构(XANES)结果表明金属原子与载体之间存在着强相互作用.实验和理论研究均表明该类催化剂在CO氧化反应、水煤气转化及乙炔加氢生成乙烯等反应中具有高的催化活性和稳定性.采用化学气相沉积法和原子层沉积法等方法可以将金属原子稳定地负载在具有缺陷活性位点的石墨烯、MXene及六方氮化硼等二维材料上并相应制备出SACs.X射线吸收精细结构谱(EXAFS)和XANES分析表明样品中金属以单原子形式存在,而且金属原子与载体之间也存在着强相互作用,理论计算表明金属原子与二维载体之间的电荷转移是SACs活性高的主要原因.置换反应法和连续还原法是制备溶胶型SACs的有效方法,其中置换反应法可将活性金属原子原位组装在金属模板团簇的顶点位置,连续还原法可将活性原子负载于金属模板团簇的表面.DFT计算表明活性原子和金属模板团簇之间存在电荷转移效应,这是溶胶型SACs具有非常高的催化活性的主要原因.SACs下一步的研究方向可能是:(1)研究开发新型SACs,尽可能提高催化剂中活性金属原子的含量;(2)深入研究SACs的结构、活性以及催化机理之间的关系;(3)尝试将SACs大规模应用于工业催化. 展开更多
关键词 单原子催化剂 制备方法 催化活性 表征 电子结构
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Acupoint injection for asthma:Systematic review of randomized controlled trials
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作者 Pei Xue liqiong wang +4 位作者 Mei Han Wenyuan Li Ning Liang Guoyan Yang Jianping Liu 《Journal of Traditional Chinese Medical Sciences》 2016年第1期22-36,共15页
Objective:To assess the effectiveness and safety of acupoint injection for the treatment of asthma.Methods:Six electronic databases were searched for randomized controlled trials(RCTs)of acupoint injection for asthma.... Objective:To assess the effectiveness and safety of acupoint injection for the treatment of asthma.Methods:Six electronic databases were searched for randomized controlled trials(RCTs)of acupoint injection for asthma.Two authors extracted data and assessed methodological quality independently using the Cochrane Collaboration Risk of Bias tool.Data were evaluated using RevMan v5.2.Results:Eighteen RCTs involving 1913 participants with asthma were identified.Overall methodological quality of the RCTs was classified as unclear risk of bias.Western medicine(12 RCTs)was injected most frequently into acupoints,followed by Chinese herbal medicine(four RCTs),vitamins(one RCT),and Chinese herbal medicine combined with Western medicine(one RCT).Four RCTs used only one acupoint[ST36(two RCTs),BL13,CV22],whereas the other RCTs selected multiple acupoints(among which BL13 was used most frequently).One RCT reported mortality,no RCT reported quality of life,15 RCTs reported the symptom improvement rate,one RCT reported asthma control test(ACT)data,one RCT reported the duration of asthma,three RCTs reported the mean time that asthma was controlled(MTAC),and 13 RCTs reported lung-function tests(LFTs).Some RCTs showed acupoint injection may improve the attack time of asthma,MTAC,and LFTs.Five RCTs reported the outcome of adverse events and showed no significant differences between the acupoint injection group and control group.Conclusions:The findings suggest that acupoint injection may be effective for improving ACT data,duration of asthma,MTAC and LFTs.However,the evidence is insufficient owing to the poor methodological quality of the RCTs. 展开更多
关键词 Acupoint injection ASTHMA Randomized controlled trial Systematic review
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单原子催化剂合成方法 被引量:4
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作者 吴文浩 雷文 +2 位作者 王丽琼 王森 张海军 《化学进展》 SCIE CAS CSCD 北大核心 2020年第1期23-32,共10页
单原子催化剂作为一种原子尺度的催化剂,在制氢、CO氧化及光催化等领域均具有广阔的应用前景。大量实验结果和理论计算证实了金属单原子和载体之间的相互作用,及由两者之间电荷转移引起的电子结构改变是单原子催化剂具有高的选择性和催... 单原子催化剂作为一种原子尺度的催化剂,在制氢、CO氧化及光催化等领域均具有广阔的应用前景。大量实验结果和理论计算证实了金属单原子和载体之间的相互作用,及由两者之间电荷转移引起的电子结构改变是单原子催化剂具有高的选择性和催化活性的主要原因。本文着重综述了近年来共沉淀法、化学还原法及浸渍法所制备单原子催化剂的催化性能,并进行展望。 展开更多
关键词 单原子催化剂 共沉淀法 化学还原法 浸渍法
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Effect of particle size on the thermal performance of NaNO3/SiC)2/C composite phase-change materials
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作者 Liang Liu liqiong wang +2 位作者 Weichun Ge Yanfeng Ge Yun Huang 《Particuology》 SCIE EI CAS CSCD 2019年第3期169-175,共7页
Storage of thermal energy is a key technology for energy conservation and application of renewable energy sources. In this paper, the thermal performance of inorganic composite phase-change materials (PCMs;NaNO3/SiO2/... Storage of thermal energy is a key technology for energy conservation and application of renewable energy sources. In this paper, the thermal performance of inorganic composite phase-change materials (PCMs;NaNO3/SiO2/C) is studied under extreme thermal conditions and the effect of raw particle size is examined. We designed a thermal shock test platform with a diffusive combustion system and in-situ infrared thermal imaging. The influences of the heat flux magnitude and exposure time on the performance of the PCMs were examined under vertical thermal shock conditions. Leakage of molten salt in the composite PCMs was observed as the heat flux reached a threshold point. The morphology and thermal properties were characterized by ex-situ SEM, XRD, DSC, and BET. Raw particles with sizes in the range of 105-500 μm were used to synthesize the composite material and examine its role in thermal shock behavior. Our experiments showed that deterioration of the thermal storage density was slowed as the particle size was increased. This work provides useful guidance for improving the anti-thermal shock ability of future material designs. 展开更多
关键词 THERMAL STORAGE Phase CHANGE material PARTICLE SIZE THERMAL shock DECOMPOSITION temperature
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