电泳沉积(EPD)是指悬浮的胶体颗粒在电场作用下从悬浮液中沉积到基质上的过程。EPD法可以有效控制石墨烯层数,是生产石墨烯薄膜和石墨烯基复合材料的有效方法。山西大学王梅教授课题组联合挪威东南大学对采用电泳法制备石墨烯基材料及应用进行了综述。该文章发表在Journal of Materiomics第4卷第2期,题目为Electrophoretic deposition of graphene-based materials: A review of materials and their applications。您可以点击文末“阅读全文”免费下载!
Ma Y, Han J, Wang M, Chen X, Jia S. Electrophoretic deposition of graphene-based materials: A review of materials and their applications. Journal of Materiomics 2018; 4(2): 108-120. https://doi.org/10.1016/j.jmat.2018.02.004
内容梳理
EPD通常在两电极电池中进行,其中电场可以是直流电模式,也可以是调制电流模式(图1)。EPD法可以应用于悬浮颗粒尺寸小于30μm的任意胶体系统。 EPD法制备石墨烯基材料的包括2个步骤:电泳和沉积。将电场施加到石墨烯悬浮液时发生电泳,带电的石墨烯薄片受到电力的驱动下向带相反电荷的电极移动,随后,石墨烯薄片在电场力的作用下不断在电极表面上累积发生沉积过程。
有关EPD法制备石墨烯的理论和模拟已有研究,还研究了诸如电导率,溶剂,电势,电场,浓度等电化学参数对EPD法制备石墨烯基材料的影响。EPD法依赖于石墨烯片在悬浮液中获得电荷的能力。稳定的石墨烯悬浮液是EPD法制备石墨烯的先决条件,这意味着石墨烯薄片必须均匀分散在溶剂中并彼此独立地向电极移动,这样才不会发生团聚并有可能实现石墨烯片的重新排列。
Fig. 1. Schematic diagram of EPD of charged graphene flakes on the anode of an EPD cell with planar electrodes.
GO和RGO主要用作EPD制备石墨烯的前驱体,由于它们具有含氧官能团,易于制备石墨烯悬浮液。水溶液比有机溶液更广泛地用于EPD法制备石墨烯,因为它具有较低的EPD电压并且对环境更友好。此外,水溶液还具有较快的动力学、适用于较高温度且成本较低。然而,水溶液也因为电化学副反应经常与EPD一起发生,例如水的电解,金属电极的氧化等,影响EPD效率和沉积物的均匀性。EPD法制备石墨烯的可分为两种:阴极EPD和阴离子EPD。
采用EPD,可以在具有任意形状和表面的基底上发生多种形式的沉积,包括板状基底上连续的平面膜,纤维或其他不规则基底,多孔沉积物,垂直排列的石墨烯沉积物,电极上的不连续沉积,图案化的石墨烯沉积物等。EPD法制备的石墨烯片会表现出不同的形态,这取决于沉积条件,例如基材形态,EPD石墨烯前驱体,后处理技术等。
Fig. 4 Different forms of graphene deposits obtained by EPD. (a), An EPD RGO membrane with a layer-by-layer morphology [31]. (b), The Porous morphology of EPD graphene with post-treatment of freeze-drying [5]. (c), GO nanowalls on a graphite rod electrode with the GO flakes vertically aligned [11]. (d), EPD of graphene with fine-size graphene as precursor. (e), EPD of graphene with large-size graphene as precursor [44].
越来越多人采用EPD法制备石墨烯基复合材料,包括:(i)石墨烯/非金属纳米颗粒复合材料如石墨烯/ CNT,石墨烯/炭黑,石墨烯/ Si; (ii)石墨烯/金属基纳米颗粒复合材料,例如石墨烯/金属,石墨烯/金属氧化物,石墨烯/矿物,石墨烯/金属氢氧化物;(iii),石墨烯/聚合物材料。
为了制备石墨烯增强复合材料,交错的多孔结构和纳米颗粒间隔的石墨烯薄膜,制造石墨烯/纳米颗粒复合材料的EPD法主要可分为3种类型,如图6所示。EPD悬浮液由石墨烯和一种或多种其他组分组成,以三种形式稳定地分散:(I)同时沉积分别分散的石墨烯薄片和纳米颗粒;(II)分散石墨烯薄片并将具有相反电荷的纳米粒子在石墨烯表面上自组装,胶体的总电荷取决于哪个组分具有更高的zeta电位;(III),在EPD前,石墨烯与大分子(聚合物链)混合在一起。
Fig. 6. Three different strategies to fabricate graphene-based composite materials by co-EPD: co-dispersion of nanoparticles and graphene flakes (I), self-assembled nanoparticles and graphene flakes (II), and dispersion of graphene/polymer composite particles (III).
展望
EPD法有效且多功能,可用于生产不同应用条件的石墨烯及其复合材料,特别是用于制备石墨烯基复合材料,EPD提供了一种简便有效的方法一步制备出均匀且连接良好的复合材料,并且,通过控制EPD参数可以调控材料各组分的含量。但在某些特殊情况下,例如EPD法制备石墨烯/金属氢氧化物,EPD与电化学沉积同时发生,虽然简化了工艺,但使得机理不明确且工艺变得复杂,也很难控制形貌和各组分的含量等。即使EPD已在石墨烯基材料和应用中广泛使用,但EPD制备石墨烯的机理尚不明晰。今后应该对EPD制备石墨烯的机理进行更深入的研究,这将为控制EPD制备石墨烯的参数,采用EPD制备更多材料,消除不利的副反应提供有效的指导。
亮点
The research progress in recent 5 years of the EPD of graphene materials and their applications are summarized.
The research progress of the EPD of graphene-based composite materials and their applications are reviewed.
The discussed composite materials include graphene/nanoparticles (nonmetal and metal based) and graphene/polymers.
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Yifei Ma is currently an assistant professor at the State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, China. He obtained his Ph.D. degree in 2016 from Sungkyunkwan University, South Korea, and joined Shanxi University afterward. His research interests include synthesis and functionalization of low-dimensional materials and the applications.
Jiemin Han is a master candidate under the supervision of Prof. Xuyuan Chen and Prof. Yifei Ma at Shanxi University. He earned his Bachelor's degree from Shanxi Normal University (China) in 2017. His current research interests are 2D materials and their electrochemical properties.
Mei Wang is currently a professor at the State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University. She received her Ph.D. degree in 2014 from the Sungkyunkwan University, South Korea, and worked at Sungkyunkwan University as a post-doctoral researcher until 2017. Her research interests include graphene-based materials, electrophoretic deposition, electrode materials for energy storage devices, electrochemical sensing, etc.
Xuyuan Chen is a professor at the State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, China. He also works at Department of Micro- and Nanosystem Technology, University College of Southeast Norway. He was awarded the “Thousand Talent Program” from China in 2010. His research focuses on low dimensional materials, supercapacitors, Micro- and Nano-technology and systems, laser displays and speckle reduction, etc.
Suotang Jia is a professor at the State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, China. He earned his Ph.D. degree in 1994, from East China Normal University, China. His research fields include functional materials, low-dimensional materials, laser spectroscopy, quantum optics, etc.
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