Pressure-Sensitive and Conductive Carbon Aerogels from Poplars

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Pressure-Sensitive and Conductive Carbon Aerogels from Poplars Catkins for Selective Oil Absorption and Oil/Water Separation Lingxiao Li, Tao Hu, Hanxue Sun, Junping Zhang, and Aiqin Wang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • Publication Date (Web): 11 May 2017 Downloaded from http://pubs.acs.org on May 12, 2017

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ACS Applied Materials & Interfaces

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Pressure-Sensitive and Conductive Carbon Aerogels from Poplars Catkins for Selective Oil Absorption and Oil/Water Separation 13

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Lingxiao Li,†§Tao Hu,†‡ Hanxue Sun,‡ Junping Zhang,*† and Aiqin Wang† 17 19

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Key Laboratory of Clay Mineral Applied Research of Gansu Province, and State Key

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Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese 24

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Academy of Sciences, 730000, Lanzhou, P.R. China, ‡Department of Chemical 25 27

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Engineering, College of Petrochemical Engineering, Lanzhou University of 28 29

Technology, Lanzhou 730050, P.R. China, §Graduate University of the Chinese 32

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Academy of Sciences, 100049, Beijing, P.R. China 3 35

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* Address correspondence to [email protected] 36 37 38 40

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KEYWORDS: carbon aerogel, cellulose, oil absorption, pyrolysis, compressible 41 42 43 4 46

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ABSTRACT: Multifunctional carbon aerogels that are both highly compressible and 48

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conductive have broad potential applications in the range of sound insulator, sensor, 49 51

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oil absorption and electronics. However, the preparation of such carbon aerogels has 52 54

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been proven to be very challenging. Here, we report fabrication of pressure-sensitive 56

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and conductive (PSC) carbon aerogels by pyrolysis of cellulose aerogels composed of 57

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poplars catkin (PC) microfibers with a tubular structure. The wet PC gels can be dried 1 ACS Paragon Plus Environment


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directly in an oven without any deformation, in marked contrast to the brittle nature of 6

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traditional carbon aerogels. The resultant PSC aerogels exhibit ultralow density (4.3 7 9

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mg cm-3), high compressibility (80%), high electrical conductivity (0.47 S cm-1), and 10 1

high absorbency (80-161 g g-1) for oils and organic liquids. The PSC aerogels have 14

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potential applications in various fields such as elastomeric conductors, absorption of 15 17

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oils from water and oil/water separation, as the PSC aerogels feature simple 18 19

preparation process with low-cost biomass as the precursor. 21

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INTRODUCTION 26 27

Carbon aerogels with an interconnected 3D network, characterized by low density, 30

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high porosity, high electrical conductivity and chemical inertness, have received 31 3

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increasing attention in a broad range of important fields including oil absorption, 34 35

acoustic insulator, battery anodes and nuclear waste storage.1-3 Recently, various 38

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precursors such as carbon fibers, carbon nanotubes, graphene oxide and biomass (e.g., 39 41

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cotton,4 wool,5 bamboo6 and sugarcane7), have been used for the preparation of carbon 42 43

aerogels. Also, a variety of methods including chemical vapor deposition,8 sol-gel 46

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process,9 hydrothermal reduction10 and freeze-drying/pyrolysis,11 have been 47 49

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established to invent carbon aerogels. As is known to all, the preparation approaches 50 52

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have great influences on the structural framework and features of the resulting carbon 54

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aerogels. Although the reported carbon aerogels possess a series of favorable 5 57

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properties, most of the approaches still have some shortcomings. For example, the 58 60

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commonly used hydrothermal reduction and freeze-drying procedure are not only 2 ACS Paragon Plus Environment

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time-consuming, but also make the carbon aerogels very fragile owing to the 6

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formation of huge channels during ice crystal growth.12 In addition, in order to obtain 7 9

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carbon aerogels from graphene and carbon nanotubes, expensive precursors and 10 1

complex equipment are indispensable. Moreover, the acidic waste generated in the 14

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preparation process is very harmful to the environment. Therefore, the complicated 15 17

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methods, the expensive precursors and the potential environmental pollution have 18 19

largely restricted practical applications of carbon aerogels. 2

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Biomass materials are attracting significant research interests because they are low 23 25

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cost, abundant in nature and nuisanceless. Considerable efforts have been made to 26 27

create carbon aerogels with fascinating features using cellulose as the raw material. 30

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Wu et al. fabricated the ultralight carbon nanofiber aerogels from bacterial cellulose 31 3

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via freeze-drying and pyrolysis.13 Hao et al. prepared hierarchical porous carbon 34 36

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aerogels for high performance supercapacitor electrodes by carbonization of 38

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freeze-dried bagasse aerogels followed by chemical activation.14 Despite excellent 39 41

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properties of the above biomass-based carbon aerogels, their preparation required 42 43

extremely harsh and sophisticated conditions. Thus, Bi15 and Zang16 et al. fabricated 46

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carbon aerogels via single-step carbonization of raw cotton and willow catkin, 47 49

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respectively. Although the as-prepared carbon aerogels exhibit high absorbency for 50 52

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oils and organic solvents, they are seldom compressible and conductive. Until now, 54

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highly compressible and conductive carbon aerogels from cellulose are rare, 5 57

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especially those developed via simple, cost-efficient and environmental friendly 58 60

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methods. 3 ACS Paragon Plus Environment


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Poplars catkin (PC) fibers are the seed hairs of the poplar and has a high proportion 6

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of cellulosic fibers with the features of thin cell wall and large lumen.17 The very light 7 9

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PC fibers float easily in air, which often cause environmental pollution and disease 10 1

transmission in spring (Figure S1). Therefore, it is urgent to find an effective method 14

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to utilize the large amount of the PC fibers. Moreover, different from the carbon 15 17

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aerogels based on normal cellulose fibers, the tubular structure of the PC fibers makes 18 19

them very interesting building blocks for the construction of carbon aerogels with a 2

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special hollow 3D network. The tubular structure of the fibers will be helpful for the 23 25

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recovery of the carbon aerogels to their initial shape after release of the compression 26 27

force, and will also facilitate the transportation of liquids in the carbon aerogels. 30

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Here, we present a simple method for the preparation of ultralow-cost, 31 3

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pressure-sensitive and conductive (PSC) carbon aerogels from PC fibers. The PSC 34 36

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aerogels were prepared by activation of the PC fibers with sodium chlorite (SC), and 38

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then carbonization of the PC aerogels at 1000 °C in N2 atmosphere. The 39 41

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interconnected network of the PSC aerogels is formed via normal oven drying rather 42 4

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than the frequently used freeze drying or supercritical drying. Different from most of 46

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the previously reported carbon aerogels, the PSC aerogels are highly compressible 47 49

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and conductive. In addition, the electrical conductivity of the PSC aerogels is highly 50 52

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sensitive to the compressive strain, which makes them promising elasticity-responsive 54

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electric conductors. Moreover, the PSC aerogels exhibit ultralow density (4.3 mg cm-3) 5 57

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and very high absorbency for various organic liquids, originating from the tubular 58 59 60

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structure of the PC fibers, the interconnected network of the PSC aerogel and the 6

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unique preparation strategy. 7 8 9 10 12

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RESULTS AND DISCUSSION 14

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Preparation of PSC Aerogels. The route of fabricating the PSC aerogels is 15 17

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schematically illustrated in Figure 1. First, the collected PC fibers were activated in a 18 19

SC aqueous solution (10 mg mL-1) under mild acidic condition at 80 °C, and then 2

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dispersed in ethanol to form a homogeneous suspension of the SC-PC fibers. The PC 23 25

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fibers could not form cellulose aerogels without SC treatment. More importantly, the 26 27

SC-PC fibers must be dispersed in ethanol rather than water in order to maintain the 30

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original network structure of the wet SC-PC gels in the oven drying process. 31 3

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Afterwards, the suspension was filtrated in a cylinder vessel to generate the wet 34 36

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SC-PC gel, which was dried directly at 60 °C in an oven. This is fundamentally 38

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distinguished from the other complicated drying approaches in the fabrication of 39 41

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carbon aerogels, e.g., freeze-drying and supercritical drying. A slight increase in the 42 4

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volume of the SC-PC aerogels was observed in the drying process (Figure S2). This is 46

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because the SC-PC fibers recovered their original shape like the PC fibers after 47 49

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evaporation of the absorbed ethanol with low surface tension. Finally, the black PSC 50 51

aerogels with a density of as low as 4.3 mg cm-3 were fabricated by pyrolysis of the 54

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dried SC-PC aerogel at 1000 °C for 4 h in N2 atmosphere. The volume of the PSC 5 57

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aerogel is about 35% of that of the SC-PC aerogel (Figure 1). 58 59 60



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Figure 1. 26

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Schematic illustration for preparation of the PSC aerogels.

Carbonation at high temperature is important for the preparation of the PSC 27 29

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aerogels. The density of the SC-PC aerogel decreased from 10 to 4.3 mg cm-1 after 30 32

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pyrolysis, and the corresponding weight loss of the SC-PC aerogel was about 91%. To 34

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further understand the importance of carbonation, the transition from the SC-PC 35 37

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aerogel to the PSC aerogel was studied by thermal gravimetric analysis (TGA, Figure 38 40

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S3). The SC-PC aerogel showed significant weight loss (~76 %) in 245-377 °C 42

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because of decomposition of the oxygen-containing groups of the SC-PC aerogel. The 43 45

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weight of the aerogel decreased gradually with further increasing the temperature, 46 48

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owing to conversion of the organic species to carbon and formation of the PSC 50

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aerogel. The weight of the SC-PC aerogel decreased to 8.1 % when the temperature 51 53

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was increased to 1000 °C, which is consistent with the weight change of the SC-PC 54 56

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aerogel before and after pyrolysis in the tubular furnace at 1000 °C in N2 atmosphere. 58

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Compared with the SC-PC aerogel, no weight loss of the PSC aerogel was detected at 59 60

temperature below 700 °C, indicating high thermal stability. 6 ACS Paragon Plus Environment

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Figure 2. (a, b) SEM images of the PSC aerogel, (c) XPS spectra and (d) XRD 31 32

patterns of the raw PC fibers, SC-PC aerogel and PSC aerogel. 3 35

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In the preparation of the PSC aerogel, the activation with SC has a negligible 36 38

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influence on the surface morphology and the tubular structure of the PC fibers (Figure 39 40

S4). After treated with SC, the PC fibers kept the smooth and hollow tubular structure 43

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with a diameter of ~5 μm and a length of several millimeters. These are interesting 4 46

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and unique characters that most of cellulose fibers do not possess.18-19 However, the 47 48

hollow fibers were partly flattened and the surface of the fibers became rough after 51

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pyrolysis at 1000 °C in N2 atmosphere according to the scanning electron microscopy 52 54

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(SEM, Figures 2a-b and S4). Therefore, the structural framework of the PSC aerogels 5 56

are completely rely on that of the SC-PC aerogels. 58

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To investigate the transformation from the raw PC fibers to the PSC aerogels, the 6

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Fourier transform infrared (FTIR) spectra of the raw PC fibers, the SC-PC aerogel and 7 9

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the PSC aerogel are shown in Figure S5. Many typical functional groups of cellulose, 10 1

such as -OH (3429 cm-1), C-H (2923 cm-1), C-O (1738 and 1240 cm-1), C=C (1629 14

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cm-1), C-O-C (1114 cm-1) and C-O (1046 cm-1), were detected in the spectrum of the 15 17

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raw PC fibers. Although the treatment with SC could break a part of hydrogen 18 19

bonding and oxidate lignin of the raw PC fibers,20 the FTIR spectrum of the SC-PC 2

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aerogel was very similar to that of the raw PC fibers. In addition, the main 23 25

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characteristic bands of the SC-PC aerogel at 1738 cm-1 (stretching vibration of C=O), 26 27

1240 cm-1 (stretching vibration of C-O) and 1114 cm-1 (stretching vibration of C-O-C) 30

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disappeared after pyrolysis. Moreover, the intensity of the absorption bands at 1450 31 3

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cm-1 (bending vibration of C-H), 1373 cm-1 (bending vibration of C-H) and 1046 cm-1 34 36

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(stretching vibration of C-O) became extremely weak, which are attributed to 38

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carbonation of the SC-PC aerogel. 39 41

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The transformation from the raw PC fibers to the PSC aerogels was further studied 42 4

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by X-ray photoelectron spectroscopy (XPS, Figure 2c). In the XPS spectra of the raw 46

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PC fibers, the SC-PC aerogel and the PSC aerogel, the C 1s (284.8 eV) and O 1s 47 49

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(532.7 eV) peaks were detected. After SC treatment, the C/O atomic ratio decreased 50 52

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from 7.67 to 3.62 owing to the oxidation of lignin and the removal of impurity on the 54

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surface of the PC fibers (Table S1). After carbonation at 1000 °C, there is an obvious 5 57

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increase in the C/O atomic ratio to 12 on the surface of the PSC aerogel, indicating 58 60

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removal of most of the oxygen-containing groups of the SC-PC aerogel. In addition, 8 ACS Paragon Plus Environment

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the C-C peak became very strong and the C-O peak disappeared according to the high 6

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resolution C 1s spectra of the SC-PC aerogel and the PSC aerogel (Figure S6). 7 9

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The structural changes from the raw PC fibers to the PSC aerogel were analyzed 10 1

according to their X-ray diffraction (XRD) patterns (Figure 2d). The PC fibers 14

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showed two strong characteristic peaks at 2θ of 15.43°and 22.42°, corresponding to 15 17

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the typical (110) and (020) planes of cellulose, respectively. After treatment with SC, 18 19

no obvious change of these two peaks was detected. However, the peak at 15.43° 2

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disappeared and the peak at 22.42°became extremely weak according to the XRD 23 25

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pattern of the PSC aerogel, which means that the crystalline structure of the PC fibers 26 27

has been destroyed and amorphous carbon has been formed in the pyrolysis process. 30

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Mechanical Properties and Electrical Conductivity of PSC Aerogels. Excellent 31 3

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mechanical performance is very important for carbon aerogels in order to achieve the 34 36

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recyclable applications. The PSC aerogels are highly compressible and could sustain 38

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large deformation (Figure S7). Figure 3a presents the compressive stress-strain curves 39 41

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of the PSC aerogel with different strain (40%, 60% and 80%). There are two 42 4

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strikingly different stages during the whole loading process. The PSC aerogel 46

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exhibited linear elastic deformation under low compressive strain followed by 47 49

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inelastic hardening and densification under high compressive strain. The compressive 50 52

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stress increased with the strain inch by inch when the strain was below 40% owing to 54

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elastic bending of the fibers. With further increase of the compressive strain to above 5 57

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60%, a densification region with a rapidly increased slope was observed because of 58 60

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impinging among the fibers. In addition, the PSC aerogel could even withstand 9 ACS Paragon Plus Environment


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compression up to 80% and could almost recover its original shape after release of the 6

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compression force. Moreover, the stress maintained above zero and almost returned to 7 9

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the initial points in the overall cyclic compression process, indicating the high 10 1

elasticity of the fibers and excellent structural stability of the PSC aerogel. 13

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Figure 3. Compressive cyclic stress-strain curves of the PSC aerogels with different 49 51

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(a) strain and (b) cycle. 53

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The PSC aerogel was subjected to a successive cyclic compression test with 500 54 56

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loading-unloading cycles at 50% strain (Figure 3b). After 500 cycles, the PSC aerogel 57

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still retained its original shape without fracture or collapse. Only 0.04% deformation


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at the 500th cycle was recorded, which is much lower than many polymeric foams and 6

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cellulose aerogels. Additionally, the maximum compressive stress was only reduced 7 9

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by 18.97% after 500 compression cycles at 50% strain (Figure S8). These results 10 1

showed the robust mechanical performance of the PSC aerogel, which is attributed to 14

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both the unique tubular structure of the PC fibers and the porous skeleton of the PSC 15 17

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aerogel. It is noteworthy that the PSC aerogel exhibits more stable mechanical 18 19

properties than the carbon aerogels from winter melon, carbon nanotubes and 2

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graphene (Table S2). 21-22 23 24 25 26 27 28 29 30 31 32 3 34 35 36 37 38 39 40 41 43

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Figure 4. 45

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Compressive properties and electrical conductivity of the PSC aerogel

and the carbon aerogels from cellulose7, 18, 23-25 and CNTs and graphene,1, 22, 26-35 and 46 48

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silicone sponges.36-40 49 51

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Besides excellent compressibility, the PSC aerogel showed a high electrical 53

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conductivity of 0.47 S cm-1, which is higher than those of the carbon aerogels from 54 56

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cellulose.13 Also, this makes the PSC aerogel different from the common silicone 57

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sponges that are not electrically conductive (Figure 4). Although the electrical



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conductivity of the PSC aerogel is inferior to the carbon aerogels from CNTs (~0.67 S 6

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cm-1)27 and graphene (~2.62 S cm-1)34, the PSC aerogel have both excellent 7 9

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compressibility and good electrical conductivity simultaneously (Table S2 and Figure 10 1

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Figure 5. (a) Strain-controlled on-off of a LED lamp using the PSC aerogel, variation 39 41

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of R/R0 of the PSC aerogel with (b) compressive strain in one cycle and (c) repeatedly 42 4

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compression for 10 cycles at 50% strain. 46

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Benefiting from the excellent compressive properties and high electrical 47 49

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conductivity, the PSC aerogel is promising to be used as a kind of elastomeric 50 52

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conductor. A LED lamp can be highly illuminated when linked to a circuit using the 54

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PSC aerogel. The fluctuation of the brightness depends on compressing and releasing 5 57

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of the aerogel (Figure 5a and Movie S1). As can be seen, the larger the deformation of 58 60

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the PSC aerogel, the brighter the lamp was. Meanwhile, the electrical resistance is 12 ACS Paragon Plus Environment

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sensitively replied on the compressive strain of the PSC aerogel. The variation of 6

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electrical resistance of the PSC aerogel with compressive strain was systematically 7 9

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investigated and the results are shown in Figure 5b. By loading pressure on the PSC 10 1

aerogel, the normalized electrical resistance (R/R0) decreased almost linearly to 14.8 % 14

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with an increase of the compressive strain to 50%. This stemmed from the increased 15 17

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contact points among the fibers during the compression process. Once the loading was 18 19

removed, the contact area among the fibers is smaller than that of the original aerogel 2

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due to minor dents on the surface of the hollow fibers, leading to a slight increase in 23 25

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the electrical resistance. In addition, the R/R0 of the PSC aerogel maintained very 26 27

stable in the ten cycles of the cyclic compression test at 50% strain, implying long 30

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working life and reliability of the PSC aerogels as elastomeric conductors (Figure 5c). 31 3

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Wettability of PSC Aerogel and Its Applications for Oil Absorption and 34 36

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Oil/Water Separation. The PSC aerogel is also an ideal candidate for absorption and 38

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recycling of oils and organic solvents from wastewater because of their 39 41

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superhydrophobicity/superoleophilicity (CAwater ~ 150.3°, CAtoluene ~ 0°) and high 42 4

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porosity (Figure S9 and Movie S2). As shown in Figure 6a, the PSC aerogel absorbed 46

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the floating oil within several seconds when the aerogel contacted with the oil on the 47 49

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surface of water. Owing to the ultralow density and superhydrophobicity, the PSC 50 52

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aerogel remained floating on the water surface after absorption of the oil, benefiting 54

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for recovery and recycling of the PSC aerogel (Figure S9c). Moreover, the PSC 5 57

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aerogel can be used for efficient oil/water separation (Figure 6b). When 20 mL of 58 60

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oil/water mixture was poured onto 1.14 cm3 of the PSC aerogel, the oil was quickly 13 ACS Paragon Plus Environment


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absorbed by the PSC aerogel and the excess oil penetrated through the PSC aerogel 6

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and dropped into the beaker beneath it. Meanwhile, water was repelled and collected 7 9

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on the surface of the aerogel. The separation process completely depends on the 10 1

gravity of the oil/water mixture without any external force. 13

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Figure 6. (a) Absorption of floating oil on the surface of water and (b) oil/water 42 4

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separation using the PSC aerogel. (c) Absorbency of the PSC aerogel for various oils 46

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and organic liquids, and (d) variation of absorbency of the PSC aerogel for toluene 47 49

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with absorption cycles. (e) Burning the PSC aerogel with absorbed oil using an open 50 52

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flame. The oil in (a, b) and water in (b) were dyed with oil red O and methylene blue, 54

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respectively. 5 57

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The porous 3D network and the tubular structure of the PSC aerogel provide 58 60

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abundant space for the uptake of oils and organic liquids. As shown in Figure 6c, the 14 ACS Paragon Plus Environment

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PSC aerogel exhibits very high absorbency of 81 to 161 g g-1 for various oils and 6

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organic liquids including petroleum products and non-polar solvents. The oil 7 9

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absorbency is a bit lower than those of the carbon nanofiber aerogel from bacterial 10 1

cellulose (106-312 g g-1)13, the graphene aerogel (100-260 g g-1)41 and the assembled 14

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carbon aerogel (215-913 g g-1)42. However, the absorbency of the PSC aerogel is 15 17

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considerably superior to those of the carbon aerogel from winter melon (16~50 g 18 19

g-1)43, the carbon microbelt aerogel (~151 g g-1),11 and the carbon aerogels from 2

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graphene and carbon nanotubes34, 44-48 as well as other sponges49 37, 39, 50-53 (Table S2 23 25

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and Figure 7). Above all, the fabrication method of the PSC aerogel is simpler and the 26 27

precursor is the most cost-effective among all these aerogels. 29

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Figure 7. Density and oil absorbency of the PSC aerogel and the carbon aerogels 47 49

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from cellulose11, 50

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and CNTs and graphene,1,

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and silicone

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sponges.37, 53-54 54

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The recyclability of aerogels is one of the key criteria for oil cleaning-up 5 57

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applications. The PSC aerogel can be reused for absorbing organic liquids after dried 58 60

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in an oven directly. The absorbency of the PSC aerogel is very stable, and remains 15 ACS Paragon Plus Environment


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about 80 g g-1 of toluene after repeatedly used for 10 cycles as shown in Figure 6d. 6

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Moreover, combustion was also employed as an alternative method for treating the 7 9

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oil-loaded PSC aerogel. When ignited using an open flame, the PSC aerogel still kept 10 1

its skeleton intact after complete combustion of the oil in 45 s, indicating excellent 14

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retardant property of the PSC aerogel (Figure 6e). The absorbency of the PSC aerogel 15 17

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slightly decreased with increasing the absorption-combustion cycles (Figure S10a), 18 19

because the volume of the PSC aerogels gradually decreased in the combustion 2

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process (Figure S10b). The PSC aerogel was ignited for 45 s per cycle. In addition, 23 25

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the density of the PSC aerogel slightly increased to 4.42 mg cm-3 after 10 26 27

absorption-combustion cycles (Figure S10c). Therefore, the PSC aerogel can be 30

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recycled and repeatedly used via evaporation or combustion of the absorbed oils. 31 32 3 34 36

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CONCLUSIONS 38

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In summary, we have report fabrication of ultralight and versatile pressure-sensitive 39 41

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carbon aerogels based on low-cost natural biomass, PC fibers, through a simple 42 4

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approach. The wet SC-PC gels can be dried directly in an oven without any 46

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deformation, in marked contrast to the preparation of traditional carbon aerogels. The 47 49

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PSC aerogels possess ultralow density, high compressibility, high electrical 50 52

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conductivity, high oil absorbency and excellent fire resistance. By exploiting the 54

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excellent mechanical properties and electrical conductivity of the PSC aerogel, we 5 57

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have demonstrated the great potential of the PSC aerogels as pressure sensors. 58 60

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Moreover, the PSC aerogels are a kind of very good materials for the cleaning-up of 16 ACS Paragon Plus Environment

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oily water. Distillation and combustion can be used for the recycling of the PSC 6

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aerogel after absorption of oils owing to its good thermal stability and fire resistance. 7 9

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We believe that the PSC aerogel should find a broad range of applications including 10 1

sensors, environmental remediation and 3D electrodes, as the PSC aerogels with 14

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excellent properties can be prepared using low-cost natural biomass through a simple 15 17

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approach. 18 19 20 21 2

MATERIALS AND METHODS 23 24 26

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Materials. Raw PC fibers were collected from Lanzhou, China. Anhydrous ethanol, 27 28

sodium chlorite, acetic acid, methylene blue, oil red O, toluene, n-hexane, petroleum 29 31

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ether, dichloromethane and chloroform were purchased from China National 32 34

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Medicines Co., Ltd., China. Other reagents used were all of analytical grade. 35 36

Deionized water was used throughout the experiment. All chemicals were used as 39

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received without further purification. 40 42

41

Preparation of Suspensions of SC-PC Fibers. 2.0 g of the raw PC fibers were 43 4

washed in turn with 40 mL of water and 40 mL of ethanol. SC (1.0 g) was dissolved 47

46

45

in 100 mL of deionized water in a flask equipped with a mechanical stirrer and a 48 50

49

thermometer. The pH of the SC solution was adjusted to 4.5 using 0.3 mL of acetic 51 52

acid. Afterwards, 2.0 g of the PC fibers were added into the SC solution and stirred at 5

54

53

1000 rpm and 80 °C. The as-prepared SC-PC fibers were washed with deionized 56 58

57

water until pH 6, and then washed with anhydrous ethanol for three times to remove 59 60



Page 18 of 37

1 2 3

the residual water. Finally, the SC-PC fibers were re-dispersed in 150 mL of 6

5

4

anhydrous ethanol to form the homogeneous suspensions of the SC-PC fibers. 7 9

8

Fabrication of PSC Aerogels. The suspension of the SC-PC fibers in ethanol was 10 1

homogenized at 12000 rpm for 20 min. After that, the suspension was poured into the 14

13

12

desired mould, filtered to yield the wet SC-PC gels with diverse shapes, and then 15 17

16

dried directly in an oven at 60 °C. Finally, the dried SC-PC aerogels were carbonized 18 19

in N2 atmosphere at 1000 °C for 4 h with a ramp rate of 5 °C min-1, and then cooled 2

21

20

down naturally to room temperature. 23 25

24

Characterization. The micrographs of the samples were taken using a field 26 27

emission scanning electron microscope (SU8020, Hitachi Limited, Japan). Before 30

29

28

SEM observation, all samples were fixed on aluminum stubs and coated with gold (~7 31 3

32

nm). Digital micrographs of samples were taken using a Leica DM1000 microsystem 34 36

35

(CMC GmbH, Germany). The XRD patterns of the samples were obtained on an 38

37

X’pert PRO diffractometer with working conditions of Cu Kα, 30 mA and 40 kV (λ = 39 41

40

1.54060 Å). The scanning was made at room temperature between 10°and 80°in 2θ 42 4

43

with a scanning speed of 0.02°per second. FTIR spectra of the samples were recorded 46

45

on a Nicolet NEXUS FTIR spectrometer using potassium bromide pellets. XPS 47 49

48

spectra of the samples were obtained using a VG ESCALAB 250 Xi spectrometer 50 52

51

equipped with a monochromated Al Kα X-ray radiation source and a hemispherical 54

53

electron analyzer. The spectra were recorded in the constant pass energy mode with a 5 57

56

value of 100 eV, and all binding energies were calibrated using the C 1s peak at 284.6 58 60

59

eV as the reference. The TGA curves were obtained using a STA 6000 (PerkinElmer 18 ACS Paragon Plus Environment

Page 19 of 37


1 2 3

Instrument Co., Ltd. USA) to investigate thermal stability of the samples over a 6

5

4

temperature range of 0 to 1000 °C at a rate of 10 °C min-1 in N2 atmosphere. The 7 9

8

mechanical properties of the samples were measured using a universal testing 10 1

machine (CMT4304, Shenzhen SANS Test Machine Co. Ltd., Shenzhen, China) 14

13

12

equipped with a 50 N load cell at room temperature. The strain ramp rate was 20 mm 15 17

16

min-1. The electric resistance of the samples was measured using a digital multimeter. 18 19

Measurement of contact angles was performed at 25 °C using water drops of 5 μL on 2

21

20

a Contact Angle System OCA 20 (Dataphysics, Germany). 23

For the contact angle

25

24

measurement, the syringe was positioned in a way that the droplet of water could 26 27

contact surface of the samples before leaving the needle. All the measurements of 30

29

28

compressive stress-strain curves, variation of R/R0 with compressive strain, oil 31 3

32

absorbency as well as contact angles of the samples were carried out for six times and 34 36

35

the average values were presented. 37 38 39 41

40

Conflict of Interest: The authors declare no competing financial interest. 42 4

43

Acknowledgement. This work is supported by the "Hundred Talents Program" of the 46

45

Chinese Academy of Sciences. 47 49

48

Supporting Information Available: SEM, TGA, FTIR spectra, XPS spectra, digital 50 52

51

images and videos. This material is available free of charge via the Internet at 54

53

http://pubs.acs.org. 5 56 57 58 60

59

REFERENCES 19 ACS Paragon Plus Environment


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Carbon Aerogel from Winter Melon for Highly Efficient and Recyclable Oils and 21 2

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(RGO) 29

Modified

Spongelike

Polypyrrole

(PPy)

Aerogel

for

Excellent

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24

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32

Carbon Aerogels for the Removal of Oil Contaminants from Water. ACS Appl. Mater. 34 36

35

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40

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43

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48

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Superhydrophobic Bridged Silsesquioxane Aerogels with Tunable Performances and 53 54

Their Applications. ACS Appl. Mater. Interfaces 2015, 7, 2016-2024. 5 56 57 58 59 60



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3

(54) Pham, V. H.; Dickerson, J. H. Superhydrophobic Silanized Melamine 5 6

Sponges as High Efficiency Oil Absorbent Materials. ACS Appl. Mater. Interfaces 7 9

8

2014, 6, 14181-1418. 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 3 34 35 36 37 38 39 40 41 42 43 4 45 46 47 48 49 50 51 52 53 54 5 56 57 58 59 60


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Table of Contents Graphic and Synopsis 5

4 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 3 34 35 36 37 38 39 40 41 42 43 4 45 46 47 48 49 50 51 52 53 54 5 56 57 58 59 60



1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 31

30 80x53mm (300 x 300 DPI)

32 3 34 35 36 37 38 39 40 41 42 43 4 45 46 47 48 49 50 51 52 53 54 5 56 57 58 59 60

ACS Paragon Plus Environment

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1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 3 34 35 37

36 101x85mm (300 x 300 DPI)

38 39 40 41 42 43 4 45 46 47 48 49 50 51 52 53 54 5 56 57 58 59 60 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 3 34 35 36 37 38 39 40 41 42 43 4 45 46 48

47 130x209mm (300 x 300 DPI)

49 50 51 52 53 54 5 56 57 58 59 60


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1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 3

32 60x45mm (300 x 300 DPI)

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1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 34

3 92x71mm (300 x 300 DPI)

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37 107x95mm (300 x 300 DPI)

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1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 34

3 61x46mm (300 x 300 DPI)

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1 2 3 4 5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 2 23 24 25 26 27 28 29 30 31 32 3 34 35 44x35mm (300 x 300 DPI)

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Pressure-Sensitive and Conductive Carbon Aerogels from Poplars

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