北航程群峰教授NC：强强联合-MXene与石墨烯超韧性复合二维纳米片！- 大数跨境

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北航程群峰教授NC：强强联合-MXene与石墨烯超韧性复合二维纳米片！

科学材料站

2020-05-02

导读：本文作者提出了一种界面复合协同策略，获得了MXene功能化石墨烯复合薄膜（MrGO-AD）。该研究发现MXene纳米片与氧化石墨烯发会生Ti-O-C共价键交联的现象，并揭示了共价键交联的机理。

Published: 29 April 2020

导读

柔性还原氧化石墨烯（rGO）薄膜正被广泛应用于便携式电子器件和柔性储能系统中。然而，rGO薄膜较差的力学性能和导电性限制了其发展。本文使用MXene（M）纳米片通过Ti-O-C共价键合实现了氧化石墨烯片材的功能化。通过共轭分子（1-1-氨基吡啶-二琥珀酰亚胺基辛二酸酯，AD）使MrGO片交联。MXene纳米片和AD分子的结合减少了石墨烯片内的空隙并改善了石墨烯片的排列，从而获得了更高的致密性和韧性。原位拉曼光谱和分子动力学模拟揭示了Ti-O-C共价键合、MXene纳米片滑动和π-π桥连的协同界面作用机理。此外，基于超韧性MXene功能化石墨烯片的超级电容器可同时提供高能量和功率密度。

关键词

机械和结构特性与设备超级电容器二维材料

背景简介

rGO薄膜的缺陷

由于对移动设备，特别是对便携式电子设备和柔性储能系统的需求不断增加，柔性氧化石墨烯（rGO）正被考虑用于此类应用。然而，rGO薄膜的主要缺点是其力学性能和导电性差。增强石墨烯薄膜的一种方法是引入不同的界面相互作用，如氢键、离子键、π-π键、共价键以及不同界面相互作用的组合。

关键挑战

其中关键的挑战是如何同时提高柔性移动设备中rGO薄膜的机械性能和导电性。近年来，过渡金属碳化物(Ti₃C₂T_x，MXenes)因其高导电性、大比表面积、优异的电化学性能和良好的强度而被广泛研究。因此具有表面端接部分（T_x，例如OH、O和F）的MXene纳米片，是用于功能化GO薄膜的良好候选者。

文章介绍

近日，北京航空航天大学的院程群峰教授团队教授等人在国际知名期刊Nature Communication（2018 IF：11.878）上发表发表题为“Super-tough MXene-functionalized graphene sheets”一文。周天柱博士、吴超教授、王艳磊副研究员为第一作者。

研究者们提出了一种界面复合协同策略，获得了MXene功能化石墨烯复合薄膜（MrGO-AD）。该研究发现MXene纳米片与氧化石墨烯发会生Ti-O-C共价键交联的现象，并揭示了共价键交联的机理。同时与π堆积作用结合，实现了共价键和π堆积作用的协同效应。MrGO-AD具有超高韧性、拉伸强度和电导率，其韧性高达~42.7 MJ m^-3，而电导率达~1329.0 S cm^-1。研究者们采取原位拉曼光谱和分子动力学模拟揭示了MXene功能化石墨烯薄膜材料优异韧性的机理，这归因于MXene与石墨烯之间的Ti-O-C共价键、MXene层间滑移作用以及π堆积作用间的协同效应。通过小角散射和广角散射研究发现这种Ti-O-C共价键和π堆积作用的界面协同，不仅降低了MXene复合薄膜的孔隙率，而且还提高了石墨烯的规整度。最后，以这种超韧导电的复合薄膜为电极，组装的柔性超级电容器表现出高的体积能量密度~13.0 mWh cm-3，在0º到180º下进行17000次弯曲循环后，容量保持率仍为~98%。

文章亮点

提出了一种界面复合协同策略，获得了兼具高力学性能和高电导率的MXene功能化石墨烯薄膜

图1物理表征和相互作用

a. Schematic model of MXene-GO platelets showing the formation of Ti-O-C covalent bonding.

b. Atomic force microscope (AFM) of MXene nanosheet-functionalized GO platelets. Scale bar, 5 μm.

c. An illustration of the Mxene-functionalized GO platelets of b.

d. A photograph of a folded MrGO-AD sheet. Scale bar, 1 cm.

e. A high-resolution transmission electron microscopy (HR-TEM) image of the cross-section of the MrGO-AD sheet. Scale bar, 10 nm.

f. X-ray diffraction (XRD) patterns.

g. Comparisons of Fourier-transform infrared spectroscopy (FTIR) spectra.

h. Raman spectroscopy spectra of obtained sheets.

i. Ti 2p spectra of MXene and MGO sheets. A new peak at a binding energy of 456.5 eV indicates the formation of Ti-O-C covalent bonding between MXene and GO nanosheets.

j. Comparison of C 1s spectra. k UV-vis absorption spectra of MXene, GO, and MGO sheets.

图2：机械表征

a-d. Azimuthal scan wide-angle X-ray scattering (WAXS) patterns (for a rotating anode X-ray source) showing the full width at half maximum (FWHM) of a rGO. b MrGO. c rGO-AD. d, MrGO-AD.

e, f. The corresponding small-angle X-ray scattering (SAXS) patterns for rGO and MrGO-AD.

g. Comparison of SAXS scattering intensities for rGO and MrGO-AD. These results indicate a decrease in porosity in going from rGO to MrGO-AD.

h. Bar graphs comparing the porosity of rGO and MrGO-AD.

i. Typical tensile stress–strain curves for the investigated sheets.

j. Bar chart comparing the toughnesses and conductivity of the obtained sheets.

k. Comparison of tensile strength and toughness MrGO-AD sheet with that of other graphene-based sheets.

图3：石墨烯片的增韧机理

a–d The strain dependence of the downshift in Raman G-band frequency rGO, MrGO, rGO-AD, and MrGO-AD sheets.

e. The proposed fracture mechanism of the MrGO-AD sheet, according to molecular dynamics simulations. Ti–O-C covalent bonding between MXene nanosheets and rGO platelets (elliptical region), π-π bridging interactions between AD molecules and rGO platelets (circular region), and sliding between MXene nanosheets (rectangle region).

f–i Fracture morphology of the side views of MrGO (f, g) and MrGO-AD (h, i) sheets. Scale bar, 5 μm (f, h) and 1 μm (g, i).

图4：超级电容器的电化学表征

a. Illustration of the components of a flexible supercapacitor based on MrGO-AD sheets.

b. Cyclic voltammetry (CV) curves at scan rates of 10 to 1000 mV s⁻¹ for the MrGO-AD supercapacitor.

c. GCD curves for the MrGO-AD sheet supercapacitor.

d. Volumetric capacitance of the MrGO-AD sheet supercapacitor for current densities from 1.0 to 8.6 A cm−3.

e. Capacitance retention during the cycling of a MrGO-AD supercapacitor.

f. Volumetric energy density and power density of the MrGO-AD supercapacitor compared with alternative energy storage systems.

图5：严重弯曲对超级电容器的影响

a. Capacitance retention as a function of the bending extent of the supercapacitor (which is defined as the ratio of the end-to-end separation in the bent supercapacitor to this separation for the non-bent supercapacitor).

b. Capacitance retention for supercapacitors based on rGO, rGO-AD, MrGO, and MrGO-AD sheets during up to 17,000 bending cycles to a bending extent of 25% (which corresponds to a 180° angle between supercapacitor ends). Scale bar, 2 cm (inset).

c. Nyquist plots for a MrGO-AD supercapacitor, which were measured after various cycles of bending to the 180° angle of b.

d. Schematic diagram of three in-parallel MrGO-AD supercapacitors (both unbent and with 180° angle bending) and the corresponding circuit diagram.

e. f. Galvanostatic charge-discharge curves for three e in-parallel and f in-series MrGO-AD supercapacitors.

g–i In-series operation of three MrGO-AD supercapacitors to light an LED (~1.7 V) when in g, flat. h, 180° bent. i in twisted states. Scale bar, 2 cm (g–i).

文章链接:

https://www.nature.com/articles/s41467-020-15991-6

导师简介:

程群峰

北京航空航天大学化学学院教授，博士生导师

研究领域：主要从事仿生纳米复合材料的研究工作，围绕纳米复合材料的“界面作用及协同效应”一关键科学问题，取得了一系列研究进展，提出了一种仿生构筑高强、高韧纳米复合材料的普适性策略。