Review on Graphene-, Graphene Oxide-, Reduced Graphene Oxide-Based Flexible Composites: From Fabrication to Applications

Abstract

In the new era of modern flexible and bendable technology, graphene-based materials have attracted great attention. The excellent electrical, mechanical, and optical properties of graphene as well as the ease of functionalization of its derivates have enabled graphene to become an attractive candidate for the construction of flexible devices. This paper provides a comprehensive review about the most recent progress in the synthesis and applications of graphene-based composites. Composite materials based on graphene, graphene oxide (GO), and reduced graphene oxide (rGO), as well as conducting polymers, metal matrices, carbon-carbon matrices, and natural fibers have potential application in energy-harvesting systems, clean-energy storage devices, and wearable and portable electronics owing to their superior mechanical strength, conductivity, and extraordinary thermal stability. Additionally, the difficulties and challenges in the current development of graphene are summarized and indicated. This review provides a comprehensive and useful database for further innovation of graphene-based composite materials.

Keywords: composite; flexible devices; graphene; graphene oxide; reduced graphene oxide.

Figure 1

Various structures of graphene (0D bucky ball, 1D carbon nanotube, 3D graphite). (Reproduced with permission from ref. [9]. Copyright 2016 Springer Publications).

Figure 2

Schematic of the transformation of graphite oxide to GO and graphene. (Reproduced with permission from ref. [6]. Copyright 2016 SAGE Publications).

Figure 3

Different structures of GO. (Reproduced with permission from ref. [6]. Copyright 2016 SAGE Publications).

Figure 4

GO suspension (left side), powder, and flexible sheet (right side). (Reproduced with permission from ref. [18,21]. Copyright 2015 JNMNT and 2014 Hindawi Publications).

Figure 5

Schematic of the H₂SO₄-intercalated GO (SIGO) process. (Reproduced with permission from ref. [28]. Copyright 2013 Springer Nature Publications).

Figure 6

Graphene synthesis via the CVD method. (Reproduced with permission from ref. [6]. Copyright 2016 SAGE Publications).

Figure 7

Steps of the synthesis of GO and rGO. (Reproduced with permission from ref. [29]. Copyright 2017 Scientific Research Publications).

Figure 8

Consecutive steps in the chemical synthesis of rGO using ascorbic acid as a reducing agent. (a) Oxidation and exfoliation of graphite using Hummer’s method. (b) Reduction and conversion of Mn (VII) ions to soluble Mn (II) ions by the addition of ascorbic acid. (c) Color transition of the exfoliated graphite oxide from greenish yellow to black in the early stage of reduction. (d) Loss of hydrophilicity of GO when stirring is paused. (e) Precipitation of rGO after completion of the reduction stage and cooling down to room temperature. (f) Filtration of rGO using cellulose filter paper. (g) rGO powder after freeze-drying. (Reproduced with permission from ref. [31]. Copyright 2015 Springer Nature Publications).

Figure 9

(a) Flexible graphene paper with the size of 8 × 5 cm. (b) Graphene/PANI paper (3 cm × 1.5 cm), electrochemical deposition time of 10 min. (c,d) SEM images of the surface of graphene/PANI paper at different magnifications. (e,f) SEM images of cross sections of graphene/PANI paper at different magnifications. (g) Graphene/PANI composite papers with different electropolymerization times (From left to right: 2, 5, 10, 15 min). (Reproduced with permission from ref. [39]. Copyright 2013 RSC Publications).

Figure 10

(A) Cyclic behavior of MnO₂/ERGO//CNT ERGO. (B) Specific capacitance retention ratio of the flexible supercapacitor after inward bending by different angles or repeated bending. (Reproduced with permission from ref. [41]. Copyright 2014 Wiley Publications).

Figure 11

Electrochemical performances of TiO₂/graphene/PPy with different TiO₂ content: (a) CV curves; (b) galvanostatic charge–discharge curves; (c) cycle stability. (Reproduced with permission from ref. [43]. Copyright 2015 ACS Publications).

Figure 12

(a) Schematic diagram of the preparation of PANI-rGO/cellulose fiber composite paper. Optical images of (b) pure cellulose fiber paper and (c,d) nanostructured rGO/cellulose fiber composite paper. SEM images of (e,f) rGO-coated cellulose fiber paper, (g,h) nanostructured rGO/cellulose fiber composite paper, and (i,j) PANI-rGO/cellulose fiber composite paper. (Reproduced with permission from ref. [51]. Copyright 2014 Wiley Publications).

Figure 13

Flexible graphene paper. (Reproduced with permission from ref. [55]. Copyright 2009 ACS Publications.)

Figure 14

Supercapacitor derived from a conductive paper consisting of a lignocellulose/rGO (LRGO) composite. (Reproduced with permission from ref. [56]. Copyright 2018 Springer Nature Publications).

Figure 15

Illustration of the three steps used to prepare rGO/nano yarns (rGO/NYs). (Reproduced with permission from ref. [63]. Copyright 2013 Wiley Publications).

Figure 16

CVs of (A) rGO@actived carbon cloth (rGO@ACC) and (C) V₂O₅/polyindole@ACC. Galvanostatic charge–discharge curves of (B) rGO@ACC and (D) V₂O₅/polyindole@ACC. (Reproduced with permission from ref. [65]. Copyright 2016 ACS Publications).

Figure 17

Preparation process of rGO/MoO₃ composites. (Reproduced with permission from ref. [69]. Copyright 2015 Wiley Publications).