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碳海绵上电化学沉积Fe2O3纳米片及其增强电容性能
梁旭, 贾宇峰, 刘宗怀, 雷志斌
2020, 36(2): 1903034-0  doi: 10.3866/PKU.WHXB201903034
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摘要:
设计高性能的可压缩电极是实现可压缩电容器器件的关键,碳海绵(CS)具有理想的压缩形变,但却受制于有限的容量。本工作以CS为可压缩基底,通过恒电流沉积及低温热处理技术,在CS骨架上均匀沉积了α-Fe2O3纳米片。复合电极中Fe2O3的负载量随沉积时间的延长逐渐增加,且在沉积16 h后达到饱和。系统地考察了CS-Fe2O3复合电极在不同压力下的可压缩性能,并在三电极体系中,通过循环伏安、恒电流充放电等方法研究了CS-Fe2O3复合电极在3.0 mol·L−1 KOH电解液中的电容性能。结果表明,当复合电极CS-Fe2O3压缩率减小时,电极的内阻增大,比电容相应减小。CS-Fe2O3-12电极在电流密度为1 A·g−1时的最大比电容为294 F·g−1,且经过10000次恒电流充放电后,电容量仍然能保持初始值的81%,是一种潜在的电化学性能稳定的可压缩超级电容器电极材料。
超级电容器用相互连接的类石墨烯纳米片
魏风, 毕宏晖, 焦帅, 何孝军
2020, 36(2): 1903043-0  doi: 10.3866/PKU.WHXB201903043
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摘要:
采用氧化镁模板耦合原位氢氧化钾活化法制备了超级电容器用煤焦油基相互连接的类石墨烯纳米片(IGNSs)。所制备的IGNS具有高达2887 m2∙g−1的比表面积和大量的分级短孔。当作为超级电容器的电极材料时,在6 mol∙g−1 KOH电解液中,于0.05 A∙g−1的电流密度下,IGNS显示出313 F∙g−1的高比容;在20 A∙g−1的电流密度下,IGNS的比电容为261 F∙g−1,显示了好的倍率性能;经过10000次循环测试后,其容量保持率为92.7%,展现了优异的循环稳定性。这一工作为从芳烃分子大规模生产高性能储能用类石墨烯纳米片提供了一种简单的方法。
基于三维多孔活性炭构筑安全、高性能以及长循环寿命的锌离子混合电容器
赵攀, 杨兵军, 陈江涛, 郎俊伟, 张天芸, 阎兴斌
2020, 36(2): 1904050-0  doi: 10.3866/PKU.WHXB201904050
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摘要:
可充电水系锌离子电池因成本低、环境友好等优点,已经成为目前电化学储能领域的研究热点之一。然而锌离子电池中高容量、长循环寿命的阴极材料的开发仍然是一大难题。为了解决这一问题,本文中通过直接利用锌片做阳极和集流体,采用高比表面积的三维多孔活性炭(3DAC)做阴极构筑了一种锌离子混合电容器(ZIHC)。该ZIHC器件表现出了优异的电化学性能,具有目前文献报道的ZIHC最高的213 mAh·g−1比容量,展示出164 Wh·kg−1的高能量密度和9.3 kW·kg−1的高功率密度以及优异的循环稳定性(10 A·g−1下循环20000圈之后,容量保持率为90%,库伦效率接近100%)。我们认为这种采用高比表、三维多孔活性炭(3DAC)做阴极构筑的安全、高性能以及长寿命的水系锌离子混合电容器将为下一代高性能储能器件的开发提供新的研究思路。
综述
炭-/石墨烯量子点在超级电容器中的应用
朱家瑶, 董玥, 张苏, 范壮军
2020, 36(2): 1903052-0  doi: 10.3866/PKU.WHXB201903052
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摘要:
炭-/石墨烯量子点作为新兴的炭纳米材料,因具有独特的小尺寸效应和丰富的边缘活性位点而在高性能超级电容器电极材料的研发方面展现出巨大潜力。针对目前炭-/石墨烯量子点在超级电容器电极材料方面的应用优势和存在的关键问题,本文以炭-/石墨烯量子点、量子点/导电炭复合材料、量子点/金属氧化物复合材料、量子点/导电聚合物复合材料以及量子点衍生炭这些电极材料为脉络,梳理了近年来该领域的发展状况,尝试阐释炭-/石墨烯量子点在电极材料、复合材料和衍生炭电极材料中所起到的关键作用,最后对炭-/石墨烯量子点电极材料的发展进行了展望。本综述以期为炭-/石墨烯量子点基电极材料的研究提供一定参考和依据。
植物基多孔炭材料在超级电容器中的应用
郭楠楠, 张苏, 王鲁香, 贾殿赠
2020, 36(2): 1903055-0  doi: 10.3866/PKU.WHXB201903055
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摘要:
植物基多孔炭具有发达的孔结构、大的表面积、较为成熟的制备工艺、丰富的来源、低廉的价格,是目前商业应用范围最广的超级电容器电极材料。然而在实际应用中仍然存在着质量/体积比容量较低、倍率性能差等问题。本文针对先进电容器件的高能量密度、优异功率性能的要求,首先介绍了近年来发展的植物基多孔炭的制备方法,讨论了植物前驱体的组成和结构对其产物结构的影响以及与其电化学性能之间的构效关系,特别总结了近年来植物基超大比表面积多孔炭、中孔炭、层次化多孔炭的制备方法和电容储能性能。针对大比表面积多孔炭用于超级电容器时的体积性能不佳这一关键问题,本文还总结了提高植物基多孔炭体积电化学性能的方法。最后,对植物基多孔电极材料存在的问题进行了分析与总结,并展望了其研究前景。
二氧化锰与二维材料复合应用于超级电容器
王易, 霍旺晨, 袁小亚, 张育新
2020, 36(2): 1904007-0  doi: 10.3866/PKU.WHXB201904007
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摘要:
现如今世界正面临着与能源相关的一系列问题与挑战,科学家们致力于研究绿色高性能的能量存储器件以适应当前乃至以后长久可持续创新发展的需要。超级电容器作为一种新型的绿色能源储存装置,具有功率密度大、理论比电容高、充放电速度快、循环寿命长、安全性高、环境友好且经济等优点,为人类解决能源危机提出了可能。电极材料是影响超级电容器性能的重要因素。近些年,由于二氧化锰基超级电容器具有理论比电容高、化学稳定性好、环境友好等特点被广泛研究。同时多种二维材料也继石墨烯后被相继用作超级电容器电极材料,具有二维结构特征材料在提高双电层电容器的能量密度、改善赝电容电容器方面发挥着重要作用。实现高比电容和高倍率性能,将二氧化锰与二维材料复合将不失为一个有前景的选择。本文系统介绍了以石墨烯为代表的各类二维材料与二氧化锰复合物在超级电容器中的应用研究,并聚焦于这些二维材料与二氧化锰复合后所展现的优异电化学性能。
静电纺纳米纤维基超级电容器无粘合剂电极材料的研究进展
田地, 卢晓峰, 李闱墨, 李悦, 王策
2020, 36(2): 1904056-0  doi: 10.3866/PKU.WHXB201904056
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摘要:
对高性能超级电容器不断增长的需求促进了无粘合剂电极材料的快速发展。静电纺纳米纤维由于具有良好的柔性、大比表面积、高孔隙率、容易制备等优点引起了研究者们的强烈关注。本文综述了静电纺纳米纤维基无粘合剂电极材料在超级电容器领域的研究进展,阐述了不同材料的设计制备过程和提升电化学性能的诸多方法,并指明了静电纺纳米纤维基超级电容器无粘合剂电极材料的发展机遇与挑战,为性能优异的无粘合剂超级电容器电极材料的进一步开发与应用拓宽了思路。
二维纳米片层孔洞化策略及组装材料在超级电容器中的应用
康丽萍, 张改妮, 白云龙, 王焕京, 雷志斌, 刘宗怀
2020, 36(2): 1905032-0  doi: 10.3866/PKU.WHXB201905032
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功率密度高、倍率性能优异和循环性能好等特性使得超级电容器在储能领域显示了巨大的应用前景。尽管二维层状材料剥离形成的纳米片层不仅可为电化学反应提供独特的纳米级反应空间,而且由其组装的层状纳米电极材料具有化学和结构上的氧化还原可逆性及纳米片层水平方向上离子或电子快速传输通道。但是,纳米片层组装电极材料在纳米片层垂直方向上离子或电子传输存在障碍,对于超级电容器功率密度和能量密度的提高及实现快速能量储存非常不利。因此,如何通过改善离子或电子的快速传输,实现超级电容器大功率密度下的高能量密度是超级电容器电极材料发展的方向之一。本文主要综述了二维层状材料剥离成纳米片层,纳米片层孔洞化策略及组装孔洞化材料在超级电容器电极材料中的应用。纳米层孔洞化技术是改善层状电极材料在纳米片层垂直方向离子或电子传输的有效手段,为实现高比电容下的高倍率性能超级电容器电极材料制备提供了方法学。最后,对开发大功率密度下的高能量密度超级电容器电极材料提出了展望。
Review
New Precursors Derived Activated Carbon and Graphene for Aqueous Supercapacitors with Unequal Electrode Capacitances
Yao Chen, George Zheng Chen
2020, 36(2): 1904025-0  doi: 10.3866/PKU.WHXB201904025
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摘要:
Carbon materials can offer various micro- and nanostructures as well as bulk and surface functionalities; hence, they remain the most popular for manufacturing supercapacitors. This article critically reviews recent developments in the preparation of carbon materials from new precursors for supercapacitors. Typical examples are activated carbon (AC) and graphene, which can be prepared from various conventional and new precursors such as biomass, polymers, graphite oxide, CH4, and even CO2 via innovative processes to achieve low-cost and/or high specific capacitance. Specifically, when producing AC from natural biomasses or synthetic polymers, either new, spent, or waste, popular activation agents, such as KOH and ZnCl2, are often used to process the ACs derived from these new precursors while the respective activation mechanisms always attract interest. The traditional two-step calcination process at high temperatures is widely employed to achieve high performance, with or without retaining the morphology of the precursors. The three-step calcination, including a post-vacuum treatment, is also the preferred choice in many cases, but it can increase the cost per capacity (kWh∙g−1). More recently, one-step molecular activation promises a better and more economical approach to the commercial application of AC, although further increase of the yield is necessary. In addition to activation, graphitization, N doping, and template control can further improve ACs in terms of the charging and discharging rates, or pseudocapacitance, or both. Considerations are also given to material structure design, and carbon regeneration during activation. Metal-organic frameworks, which were initially used as templates, have been found to be good direct carbon precursors. Various graphene structures, including powders, films, aerogels, foams, and fibers, can be produced from graphite oxide, CO2, and CH4. Similar to AC, graphene can possess micropores by activation. Self-propagating high-temperature synthesis and molten salt processing are newly-reported methods for fabrication of mesoporous graphene. Macroporous graphene hydrogels can be produced by hydrothermal treatment of graphite oxide suspension, which can also be transferred into films. Hierarchically porous structures can be achieved by H2O2 etching or ZnCl2 activation of the macroporous graphene precursor. Sponges as templates combined with KOH activation are applied to create both micro- and macropores in graphene foams. Graphene can grow on fibers and textiles by electrodeposition, dip-coating, or filtration, which can be woven into clothes with a large area or thick loading, illuminating the potential application in flexible and wearable supercapacitors. The key obstacles in AC and graphene production are high cost, low yield, low packing density, and low working potential range. Most Carbon materials derived from new precursors work very well with aqueous electrolytes. Charge storage occurs not only in the electric double layer (i.e., the "carbon | electrolyte" interface), but also via redox activity in association with the bulk and surface functionalities, and the resulting partial delocalization of valence electrons. The analysis of the capacitive electrode has shown a design defect that prevents the working voltage of a symmetrical supercapacitor from reaching the full potential window of the carbon material. This defect can be avoided in AC-based supercapacitors with unequal electrode capacitances, leading to higher cell voltages and hence higher specific energy than their symmetrical counterparts. There are also emerging ways to raise the energy capacity of AC supercapacitors, such as the use of redox electrolytes to enable the Nernstian charge storage mechanism, and of the three dimensional printing method for a desirable electrode structure. All these developments are promising carbon materials from various precursors of new and waste sources for a more affordable and sustainable supercapacitor technology.
专论
基于阵列电极的新型混合电容器
刘文燚, 栗林坡, 桂秋月, 邓伯华, 李园园, 刘金平
2020, 36(2): 1904049-0  doi: 10.3866/PKU.WHXB201904049
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摘要:
混合电容器由于兼具电池高能量密度和超级电容器高功率密度的优势,成为当前储能领域的研究热点。然而,电池电极和电容电极之间容量和功率的不平衡严重限制了混合电容器的实际性能。因此,如何实现二者的有效匹配,优化器件性能是混合电容器实用化的关键。阵列电极的使用打破传统粉末电极中不导电粘结剂对电化学动力学的限制,其独特的结构为正负极的匹配提供了新策略。此专论结合新型储能器件的研究现状以及本课题组在混合电容器方面的探索,简单探讨了混合电容器的储能机理和阵列结构作为电极材料的优势,着重介绍了本课题组近年来在混合电容器领域的研究工作,针对存在的科学问题提出了相应的解决方案,阐明了阵列电极混合电容器在柔性/可穿戴电子器件等领域的应用前景,并展望了混合电容器在未来的发展方向和挑战。
亮点
锂缺陷型高稳定富锂锰基Li1.098Mn0.533Ni0.113Co0.138O2正极材料
韦伟峰
2020, 36(2): 1907015-0  doi: 10.3866/PKU.WHXB201907015
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超洁净石墨烯薄膜
成会明
2020, 36(2): 1909042-0  doi: 10.3866/PKU.WHXB201909042
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宽窗口水系超级电容器设计新策略
杨全红
2020, 36(2): 1910030-0  doi: 10.3866/PKU.WHXB201910030
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表面电子耦合促进高效电化学析氢
吴凯
2020, 36(2): 1910033-0  doi: 10.3866/PKU.WHXB201910033
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序言
超级电容器概述
范壮军
2020, 36(2): 1907017-0  doi: 10.3866/PKU.WHXB201907017
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专访
超级电容器研究展望—范壮军教授专访
《物理化学学报》编辑部
2020, 36(2): 1907018-0  doi: 10.3866/PKU.WHXB201907018
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亮点
同分异构的胶体硫化镉半导体幻数团簇的可逆转化
刘忠范
2019, 35(5): 451-452  doi: 10.3866/PKU.WHXB201807016
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异原子占据Ag原子簇的中心核用于催化CO2生成碳碳键的反应
侯文华
2019, 35(5): 453-454  doi: 10.3866/PKU.WHXB201807017
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基于Au@PPy核壳结构纳米粒子自组装阵列的可程序化负微分电阻效应研究
韩布兴
2019, 35(5): 455-456  doi: 10.3866/PKU.WHXB201807063
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当期推荐
弛豫时间分布法分解固体氧化物燃料电池电化学阻抗谱
庄林
2019, 35(5): 457-458  doi: 10.3866/PKU.WHXB201807065
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电荷驱动水中氧化物纳米颗粒自组装的原位透射电子显微镜研究
吴凯
2019, 35(5): 459-460  doi: 10.3866/PKU.WHXB201807077
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综述
有机太阳能电池中基于苝二酰亚胺结构小分子受体进展
邓祎华, 彭爱东, 吴筱曦, 陈华杰, 黄辉
2019, 35(5): 461-471  doi: 10.3866/PKU.WHXB201806073
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摘要:
最近几年,有机太阳能电池中的非富勒烯小分子受体研究引起了人们的兴趣。其中,苝二酰亚胺(PDI)类分子因具有良好的电子传输能力,较强的电子亲和力,稳定的光、热、化学性能以及化学结构的可设计性带来的性能可调控性而得到广泛的关注。本文总结了近三年来在体异质结有机太阳能电池应用方面PDI小分子受体的研究进展,重点关注了PDI分子结构对其性能的影响,希望为以后PDI类受体分子的设计思路起到一定的启发作用。
碳基非贵金属氧还原电催化剂的活性位结构研究进展
杨晓冬, 陈驰, 周志有, 孙世刚
2019, 35(5): 472-485  doi: 10.3866/PKU.WHXB201806131
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摘要:
以热解型Fe/N/C为代表的碳基非贵金属材料被认为是当前最具潜力替代铂的非贵金属氧还原催化剂,其综合性能的进一步突破,对于推动质子交换膜燃料电池商业化应用具有重要意义。对热解型Fe/N/C催化剂活性位结构的深入认识是实现催化剂高活性位密度和高稳定性理性设计的关键。本文总结了热解型Fe/N/C活性位的研究进展,重点介绍了非晶态铁氮配位活性中心、氮掺杂和碳缺陷三类活性位构型。由于热解型Fe/N/C是非均相的,结构非常复杂,导致在活性位认识上还存在诸多争议,本文总结阐述了活性位结构的不同观点。最后,我们展望了Fe/N/C催化剂活性位研究的未来方向。
论文
正十二烷高温机理简化及验证
卢海涛, 刘富强, 王于蓝, 王成冬, 范雄杰, 刘存喜, 徐纲
2019, 35(5): 486-495  doi: 10.3866/PKU.WHXB201806081
[摘要]  (268) [HTML全文] (268) [PDF 1694KB] (268)
摘要:
由于详细化学反应机理在模拟燃烧室燃烧时,计算量极大,很难被广泛运用。为了满足工程设计要求,采用替代燃料的简化机理进行计算不失为一种行之有效的方法。本文基于误差传播的直接关系图法和敏感性分析法对正十二烷180组分1962步高温机理(温度大于1100 K)进行简化,获得40组分234步化学反应机理。在温度为1100–1650 K,压力为0.1–4 MPa条件下,采用简化机理及详细机理对不同当量比、压力下着火延迟时间进行模拟,模拟结果与实验数据吻合得较好。通过对不同压力及温度下火焰传播速度进行模拟,验证了简化机理能够正确地反映正十二烷的燃烧特性。利用C12H26/OH/H2O/CO2等重要组分随时间变化的数据,验证了简化机理能够准确描述燃烧过程反应物消耗、基团变化、生成物产生的过程,并表明该机理具有较高的模拟精度。利用该简化机理对本生灯进行数值分析,结果表明该机理能够准确地反映火焰区温度和组分浓度的变化。紧凑的正十二烷高温简化机理不仅能够正确体现其物理化学特性,而且能够用于三维数值模拟,具有较高的工程运用价值和应用前景。
固体氧化物燃料电池电化学阻抗谱差异化研究方法和分解
施王影, 贾川, 张永亮, 吕泽伟, 韩敏芳
2019, 35(5): 509-516  doi: 10.3866/PKU.WHXB201806071
[摘要]  (505) [HTML全文] (505) [PDF 1047KB] (505)
摘要:
电化学阻抗谱技术(EIS)在固体氧化物燃料电池(SOFC)中已获得广泛应用。在EIS分析过程中,研究者能够清楚地获得燃料电池内部因纯离子(电子)导电引起的欧姆电阻和因电化学过程、扩散作用引起的极化阻抗的大小,但是对于极化阻抗的构成缺乏进一步解析。本文选用传统的Ni-YSZ阳极支撑电池,通过改变测试温度、阳极运行气氛和阴极运行气氛,设计了一套完整的阻抗差异分析(ADIS)实验。并基于弛豫时间分布法(DRT)和阻抗差异分析法,系统地分析并解释了阻抗谱中各频率段对应阻抗的物理或(电)化学含义,将该类型电池阻抗谱以6个RQ并联电路予以拟合,为之后燃料电池性能稳定性的研究奠定基础。
原位透射电子显微镜观察电荷驱动的氧化物纳米颗粒水中自组装
赵喆, 卢岳, 张振华, 隋曼龄
2019, 35(5): 539-545  doi: 10.3866/PKU.WHXB201806012
[摘要]  (465) [HTML全文] (465) [PDF 2125KB] (465)
摘要:
以四氧化三钴Co3O4纳米棒为研究对象,我们利用液体环境透射电子显微镜,原位观察了四氧化三钴纳米棒在水中的自组装过程。研究发现在电子束辐照的水环境下,四氧化三钴纳米棒的晶面存在互补式自组装现象。随着纳米棒之间的距离越来越近,纳米棒之间的相对运动速率逐渐增加,纳米棒之间的相互作用力逐渐增加。通过进一步分析纳米棒的形貌发现,纳米棒的暴露晶面大多数为{100}、{110}以及{111}晶面,而Co3O4属于极性氧化物,这些晶面往往会带有一定的电荷。在液体环境下,正是由于这些易暴露面都带有不同大小的电荷,在晶面电荷的驱动下,电荷属性相反的四氧化三钴纳米棒会互相吸引,形貌结构上进行互补,实现快速驱动的纳米棒之间自组装。
ARTICLE
Perylenediimide: Phosphonium-Based Binary Blended Small-Molecule Cathode Interlayer for Efficient Fullerene-Free Polymer Solar Cells with Open Circuit Voltage to 1.0 V
Monika GUPTA, Dong YAN, Fugang SHEN, Jianzhong XU, Chuanlang ZHAN
2019, 35(5): 496-502  doi: 10.3866/PKU.WHXB201805101
[摘要]  (337) [HTML全文] (337) [PDF 607KB] (337)
摘要:
The fabrication of high-efficiency organic solar cells requires a cathode interlayer (CIF) having multiple properties such as forming an ohmic contact with the active layer, high electron conductivity, low-density traps, and hole blocking. These roles can be more completely fulfilled by using a suitable binary blended CIF rather than a single molecule based CIF. In this article, we present the roles by using binary blended PDINO (amino N-oxide perylene diimide) and QPhPBr (tetraphenylphosphonium bromide) as the CIF to fabricate fullerene-free polymer solar cells (PSCs) with PBDB-T:IDTBR, a new donor: acceptor combination, as the active layer. The high-lying lowest unoccupied molecular orbital of the acceptor and the low-lying highest occupied molecular orbital (HOMO) of the polymer with small driving force (the donor-acceptor HOMO-HOMO energy offset, ∆HOMO) for the hole transfer, both result in a high open circuit voltage (Voc). Moreover, our strategy to insert a dual mixed solution of CIF over the blended active layer better facilitates the role, which significantly improves charge extraction and collection, leading to the high Voc, short-circuit current density (Jsc), and fill factor (FF) observed in comparison to a single CIF material. It was observed that the power conversion efficiency (PCE) increases to 8.27%, with a high Voc of 1.0 V, using a binary mixture of CBL. Such tremendous improvements in Voc using well known polymer donors have not been reported till date in binary solar cell systems. This idea demonstrates that the minimum energy loss because of the small ∆HOMO of the D-A combination and the use of a dual mixed layer of CBL together present the future prospects of non-fullerene photovoltaic devices for researchers.
Bandgap Modulation of Dithienonaphthalene-Based Small-Molecule Acceptors for Nonfullerene Organic Solar Cells
Meiqi ZHANG, Yunlong MA, Qingdong ZHENG
2019, 35(5): 503-508  doi: 10.3866/PKU.WHXB201805151
[摘要]  (201) [HTML全文] (201) [PDF 1889KB] (201)
摘要:
By using photovoltaic technology, ambient solar light can be directly converted to electricity. The photovoltaic technology has been regarded as one of the most important and promising strategies to resolve the worldwide energy and pollution problems. As one type of photovoltaic technology, polymer solar cells have attracted increasing interest due to their advantages of solution processing capability, low-cost, feasibility to be fabricated on flexible substrates etc. Not until a few years ago, the fullerene derivatives had been dominated the organic photovoltaic field as the most promising acceptor materials for polymer solar cells. However, fullerene-based polymer solar cells have a power conversion efficiency bottleneck due to the relatively fixed energy levels as well as the fixed bandgaps of fullerene derivatives. Therefore, researchers started to develop nonfullerene acceptors which can be used as alternatives to replace the traditional fullerene derivatives. Compared to the fullerene derivatives, nonfullerene acceptors offer several advantages such as stronger light absorption, tunable bandgaps and frontier molecular orbital energy levels. For nonfullerene acceptors, a ladder-type fused ring is usually used as the central core which is an essential building block to tailor the bandgaps and energy levels. Although many fused ring systems have been explored for efficient nonfullerene acceptors, ladder-type angular-shape dithienonaphthalene is seldom reported as the donor unit for nonfullerene acceptors. Furthermore, the impact of thiophene bridge on the optical and photovoltaic properties of the dithienonaphthalene-based nonfullerene acceptors has never been reported. In this context, we report on the design and synthesis of a dithienonaphthalene-based small-molecule acceptor which contains thiophene bridges in between the acceptor terminals and the fused-ring donor core. Compared to the dithienonaphthalene-based small-molecule without the thiophene bridges, the resulting acceptor (DTNIT) exhibits a reduced bandgap of 1.52 eV which makes it more suitable to be blended with the benchmark large bandgap copolymer, poly[(2, 6-(4, 8-bis(5-(2-ethylhexyl)thiophen-2-yl)-benzo[1, 2-b: 4, 5-b']dithiophene))-alt-(5, 5-(1', 3'-di-2-thienyl-5', 7'-bis(2-ethylhexyl)benzo[1', 2'-c:4', 5'-c']dithiophene-4, 8-dione)] (PBDB-T). The reduced band-gap of the resulting nonfullerene acceptor can be attributed to its extended π-conjugation in comparison with the dithienonaphthalene-based acceptor without the thiophene bridges. Inverted polymer solar cells with a device configuration of indium tin oxide/ZnO/PBDB-T:DTNIT/MoO3/Ag were fabricated and characterized. Polymer solar cells based on PBDB-T:DTNIT showed an open circuit voltage of 0.91 V, an enhanced short circuit current of 14.42 mA∙cm−2, and a moderate PCE of 7.05% which is comparable to the PCE of 7.12% for the inverted device based on PBDB-T:PC71BM. Our results not only provide a method to synthesize efficient nonfullerene acceptors with reduced bandgaps, but also offer a bandgap modulation strategy for nonfullerene acceptors.
Effect of Ink Solvents on Low-Pt Loading Proton Exchange Membrane Fuel Cell Performance
Wenhui CHEN, Shengli CHEN
2019, 35(5): 517-522  doi: 10.3866/PKU.WHXB201806011
[摘要]  (220) [HTML全文] (220) [PDF 1696KB] (220)
摘要:
Owing to the scarcity of platinum, it is of high importance to develop electrodes with low platinum metal loading and to thereby improve the utilization of Pt for the commercialization of proton-exchange membrane fuel cells (PEMFCs). In comparison to conventional high-platinum electrodes, the thickness of the catalyst layer (CL) is thinner and the interatomic Pt spacing is larger for the low-Pt loading electrodes. The distribution of electrolyte ionomer and the electrode morphology, which are strongly influenced by the solvents used in the fabrication process, are therefore increasingly important factors for achieving high performance in the membrane electrode assembly (MEA). In this work, different solvents with various dielectric constants and evaporation rates were used to prepare the inks for low-Pt loading cathode (0.1 mg·cm-2) fabrication. First, the inks were fabricated by dispersing the catalyst and ionomer in different solvents which were then coated onto carbon paper to prepare the gas diffusion electrodes. The anode and cathode electrodes were then hot-pressed together with the Nafion membrane to produce the MEAs. The results showed a mixture of isopropanol-water (4:1) yielded the best-performing MEA during the single-cell tests compared to the other solvents tested. In order to elucidate the relationship between the performance of MEAs and the solvents, the structure and the surface morphology of the CL and the distribution of Nafion ionomer in the CL was characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). A comparison of the SEM and TEM images of representative samples indicated that the best performing electrode had a much improved homogeneity in the surface morphology as well as the dispersion of catalyst and ionomer. This was because of the moderate evaporation rate and better dispersion, caused by the increased hydrogen bonding and high dielectric constant, respectively. The results from dynamic light scattering (DLS) showed that the size of the catalyst and ionomer aggregates are influenced by the solvents. It is suggested that larger aggregates might help the formation of holes in the CL for gas diffusion and water removal, with the optimum size found to be around 400–800 nm. In conclusion, the MEA fabricated from the isopropanol-water solvent exhibited a significantly increased power density (1.79 W·cm-2), and the utilization of Pt was increased to approximately 0.047 mg·W-1, which is among the best-performing fuel cells reported to date.
Molybdenum Carbide Prepared by a Salt Sealing Approach as an Electrocatalyst for Enhanced Hydrogen Evolution Reaction
Zhou LIN, Linfan SHEN, Ximing QU, Junming ZHANG, Yanxia JIANG, Shigang SUN
2019, 35(5): 523-530  doi: 10.3866/PKU.WHXB201806191
[摘要]  (341) [HTML全文] (341) [PDF 1571KB] (341)
摘要:
Molybdenum carbide is regarded as an excellent substitute for Pt-based catalysts in the hydrogen evolution reaction (HER), owing to its low cost, superior catalytic performance, and long-term stability. In this work, salt-sealed molybdenum carbide was prepared using sodium molybdate and 2, 6-diaminopyridine as the reactive raw materials, followed by continuous salt sealing and calcination of the precursor under an inert atmosphere. The morphology, composition and structure of salt-sealed molybdenum carbide were determined by scanning electron microscopy, transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results indicate that salt-sealed molybdenum carbide has irregular morphology and includes nanoparticles and nanorods. A comparison of the TEM images of Mo2C with salt sealing (Mo2C/SS) and Mo2C without salt sealing (Mo2C) indicates that Mo2C/SS exhibits a smaller particle size. This suggests that salt sealing can efficiently avoid particle aggregation. The Brunauer-Emmett- Teller (BET) specific surface area of the catalysts was obtained from nitrogen adsorption/desorption isotherms. The increase in BET surface area from 2.55 to 8.14 m2·g−1 after salt sealing provides evidence for the formation of pores in the product. The results of XRD, EDS and XPS analyses show that Mo2C/SS has an orthorhombic crystal structure with molybdenum oxides on the surface, which may originate from surface oxidation. Considering the results of XPS and the turnover frequency (TOF) calculation, we can conclude that the formation of pores via salt sealing contributes to the exposure of more active sites, while simultaneously enlarging the contact area with oxygen. Therefore, higher molybdenum oxide content is generated on the surface, resulting in a lower proportion of active centers (molybdenum carbides) on the catalyst surface. Furthermore, the pseudocapacitance generated by the faradaic reaction of molybdenum oxides is superimposed on the double-layer capacitance of Mo2C catalysts, which increases the double layer capacitance. Since the effect of pseudo-capacitance on Mo2C/SS is more significant, the TOF number declines after salt sealing. Compared with Mo2C, Mo2C/SS exhibits three features that promote HER mass activity: (1) the generation of large quantities of pores via salt sealing leads to an increase in the BET surface area and exposure of more active sites, which is beneficial for improving HER performance; (2) the porous structure and enlarged surface area pave the way for effective mass and charge transfer; (3) the decrease of the Tafel slope from 145 to 88 mV·dec−1. In summary, salt-sealed Mo2C exhibited enhanced HER activity with an overpotential of 175 mV to achieve a current density of 10 mA·cm−2. The Tafel slope for HER on salt-sealed Mo2C is 88 mV·dec−1. This can be considered as the proof of the Volmer-Heyrovsky mechanism with electrochemical desorption as the rate-determining step.
Reactivities of VO1–4+ Toward n-CmH2m+2 (m = 3, 5, 7) as Functions of Oxygen Content and Carbon Chain Length
Yue ZHAO, Jiatong CUI, Jichuang HU, Jiabi MA
2019, 35(5): 531-538  doi: 10.3866/PKU.WHXB201805231
[摘要]  (224) [HTML全文] (224) [PDF 1506KB] (224)
摘要:
Vanadium oxides are one of the most important heterogeneous catalysts that are widely used to oxidize hydrocarbon molecules into value-added chemicals. In order to reveal the mechanisms and the nature of active sites, numerous experimental and theoretical studies have been reported on the reactivities of gas-phase vanadium oxide clusters toward small molecules. However, there has been very limited research on the chemical reactivity changes associated with the oxygen contents of vanadium oxides and the carbon chain lengths of alkanes. In this work, the reactions of vanadium oxide ions VO1−4+ with alkanes (n-CmH2m+2, m = 3, 5, 7) were systematically investigated by time-of-flight mass spectrometry and the reactions of VO1−3+ with pentane were further studied by density functional theory calculations. Experimental results show that in the reactions of VO+, VO3+, and VO4+ with n-C5H12, in addition to the major adsorption processes, the activation of the C―H and C―C bonds of n-C5H12 was observed. The activation of both the bonds was observed experimentally during the reaction of VO2+ with n-C5H12 with large branching ratios. Among the vanadium oxide cations studied, VO2+ shows the strongest oxidizability and the generation of lighter alkanes and alkenes dominates the reactions; VO+ is more reactive than VO3+. VO4+ pocesses only one η2-O2 unit. Due to the weak bond between VO2+ and η2-O2, the η2-O2 unit is released in VO4+/n-C5H12 system leading to the formation of VO2+; thus VO4+ cations reflect some reactivity of VO2+. Although the oxidation states in the vanadium oxide clusters increase from +Ⅲ in VO+ to +Ⅴ in VO2+ and +Ⅳ in VO3+, the reactivity does not gradually increase. Moreover, the reactivity of the mononuclear vanadium oxide cations also does not exhibit a gradually increasing trend with the increase in oxygen content. Based on the observed reactivity trend, the adsorption channels gradually become weak as the carbon chain lengths increase; meanwhile, the dehydrogenation and C―C bond activation channels gradually become obvious and some oxygen transfer products appear. Therefore, much lighter fragments of alkanes/alkenes will be obtained if linear alkanes with more carbon atoms were reacted with VO1−4+. The theoretical results are generally consistent with those obtained from the experiments. The various reaction channels and versatile reactivity of the mononuclear vanadium oxide cations investigated in this study not only offer new insights into gas-phase reactions but also shed light on the processes occurring on the surfaces of the corresponding condensed-phase catalysts.
Single-Molecule Study on the Folding of OmpT in Tween-20 Micelles
Peixuan BU, Chenhui HE, Xinsheng ZHAO
2019, 35(5): 546-554  doi: 10.3866/PKU.WHXB201806072
[摘要]  (263) [HTML全文] (263) [PDF 1439KB] (263)
摘要:
The cell envelope of gram-negative bacteria consists of the outer membrane (OM), inner membrane (IM), and periplasm. The β-barrel outer membrane proteins (OMPs) embedded in the OM perform diverse and significant functions such as signaling, transporting, and proteolysis. The OMPs of gram-negative bacteria share similar folding pathways with that of mitochondria and chloroplasts. Therefore, the study of the OMP folding mechanism not only provides insights into antimicrobial drug design but also helps elucidate mitochondrial and chloroplast biogenesis. Most knowledge about OMP folding was obtained from ensemble experiments where OMPs were usually at micromolar concentrations and prone to aggregate, which is different from the physiological environment in the cells. Unlike ensemble techniques, single-molecule detection (SMD) can measure OMPs from nano- to picomolar concentrations and prevent aggregation. In this work, we investigated the folding of OmpT, one of the OMPs, in Tween-20 and n-dodecyl β-d-maltopyranoside (DDM) micelles by SMD. We prepared monodisperse OmpT and observed both unfolded and folded OmpT in Tween-20 and DDM micelles under different urea concentrations by single-molecule fluorescence resonance energy transfer (FRET). The folded OmpT in Tween-20 is structurally similar to the native OmpT folded in DDM but exhibits weaker resistance to urea. In contrast, OmpA barely folds and OmpC hardly folds in Tween-20 micelles. We confirmed that folded OmpT forms complexes with detergent micelles and estimated the number of bound Tween-20 and DDM molecules per OmpT by fluorescence correlation spectroscopy. We compared the enzymatic activity of OmpT folded in two detergents with a fluorescent peptide as substrate, and found that the folded form of OmpT in Tween-20 possesses weaker enzymatic activity than that in DDM. We also investigated the folding properties of OmpT, OmpA, and OmpC in the presence of the β-barrel assembly machine (BAM) complex. OmpT folds efficiently in liposome even without the BAM complex; OmpA only folds with the help of the BAM complex; and OmpC does not fold with or without the BAM complex. Based on the comparison of the folding of OmpT, OmpA, and OmpC in detergent micelles and in the presence of the BAM complex, we propose that OmpT has stronger folding tendency than OmpA and OmpC, which supports the idea that the exact role of the BAM complex is dependent on the distinct folding properties of individual OMPs. Since Tween-20 is a widely used reagent to block nonspecific adsorption in SMD experiments, our results also remind people to exercise caution to prevent possible wrong interpretations caused by the interaction between proteins and Tween-20.

编委会

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《物理化学学报》第4届编委会

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名誉主编

唐有祺

北京大学

顾问编委

包信和

中国科学院大连化学物理研究所

段雪

北京化工大学

付贤智

福州大学

侯建国

中国科学技术大学

黄维

南京工业大学

LIEBER Charles M.

Harvard University

田中群

厦门大学

万立骏

中国科学院化学研究所

吴云东

北京大学

谢晓亮

Harvard University, 北京大学

杨伟涛

 Duke University

姚建年

中国科学院化学研究所

赵新生

北京大学

主编

刘忠范

北京大学

副主编

韩布兴

中国科学院化学研究所

刘鸣华

国家纳米科学中心

申文杰

中国科学院大连化学物理研究所

吴凯

北京大学

杨金龙

中国科学技术大学

庄林

武汉大学

迟力峰

苏州大学

编委

曹勇

复旦大学

陈经广

University of Delaware

陈军

南开大学

崔屹

Stanford University

邓风

中国科学院武汉物理与数学研究所

邓友全

中国科学院兰州化学物理研究所

樊卫斌

中国科学院山西煤炭化学研究所

房喻

陕西师范大学

付红兵

中国科学院化学研究所

傅强

中国科学院大连化学物理研究所

高毅勤

北京大学

郭林

北京航空航天大学

郝京诚

山东大学

侯文华

南京大学

金荣超

Carnegie Mellon University

来鲁华

北京大学

李朝军

McGill University

李隽

清华大学

李象远

四川大学

梁万珍

厦门大学

刘海超

北京大学

刘洪来

华东理工大学

刘述斌

University of North Carolina

刘义

武汉大学

刘志敏

中国科学院化学研究所

罗小民

中国科学院上海药物研究所

马晶

南京大学

孟庆波

中国科学院物理研究所

邵翔

中国科学技术大学

孙俊奇

吉林大学

谭蔚泓

湖南大学

唐智勇

国家纳米科学中心

王键吉

河南师范大学

王鹏

中国科学院长春应用化学研究所

王心晨

福州大学

王永锋

北京大学

魏子栋

重庆大学

翁羽翔

中国科学院物理研究所

吴鹏

华东师范大学

夏永姚

复旦大学

许国勤

National University of Singapore

杨俊林

国家自然科学基金委员会

余家国

武汉理工大学

尉志武

清华大学

占肖卫

北京大学

张东辉

中国科学院大连化学物理研究所

张浩力

兰州大学

张锦

北京大学

章俊良

上海交通大学

周永贵

中国科学院大连化学物理研究所

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发布时间: 2018-05-02


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通讯地址:北京市北京大学化学学院物理化学学报编辑部

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发布日期:2009-06-24 浏览: