Hierarchically Porous Carbons Derived from Biomasses with Excellent

Subscriber access provided by UNIV OF DURHAM

Functional Nanostructured Materials (including low-D carbon)

Hierarchically Porous Carbons Derived from Biomasses with Excellent Microwave Absorption Performance Zhengchen Wu, Ke Tian, Ting Huang, Wei Hu, Feifei Xie, Jingjing Wang, Mengxing Su, and Lei Li ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b17264 • Publication Date (Web): 07 Mar 2018 Downloaded from http://pubs.acs.org on March 9, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Materials & Interfaces

Hierarchically Porous Carbons Derived from Biomasses with Excellent Microwave Absorption Performance Zhengchen Wu,a Ke Tian,a Ting Huang,a Wei Hu,a Feifei Xie,a Jingjing Wang,b, c Mengxing Su,b, c and Lei Li a,* a

College of Materials and Fujian Provincial Key Laboratory of Materials Genome, Xiamen University, Xiamen 361005, China

b

Advanced Materials Academy, Luoyang Ship Material Research Institute, Xiamen 361001, China.

c

State Key Laboratory for Marine Corrosion and Protection, Luoyang Ship Material Research Institute, Qingdao 266101, China.

KEYWORDS: biomass, in-suit activation, hierarchically porous structure, carbon, microwave absorption

ABSTRACT: A variety of biomass-based carbon materials with two-level porous structure have been successfully prepared by one-step carbonization process. The first level of micro-scale pores templates from the inherent porous tissues, while the second one of nanopores is produced by the in-suit etching by the embedded alkaline metal elements. The superimposed effect of nano and micro-scale pores endows the 1 ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 2 of 29

hierarchically porous carbons (HPCs) with excellent microwave absorption (MA) performance. Among them, the spinach-derived HPC exhibits a maximum reflection loss of -62.2 dB and a broad effective absorption bandwidth of 7.3 GHz. Particularly, this excellent MA performance can be reproduced using the biomass materials belonging to different families, harvested seasons, and origins, indicating a green and sustainable process. These encouraging findings shed the insights on the preparation of biomass-derived microwave absorbents with promising practical applications.

INTRODUCTION

In the past decades, tremendous efforts dedicated to the fabrication of microwave absorbents have revealed that the superb microwave absorption (MA) performance benefits from the both rationally chosen composition and delicately designed structure.1-5 Conventional metal and metal oxide materials such as Co, Fe3O4, and NiO demonstrate impressive properties for MA applications.6-11 However, they severely suffer from the inherent drawbacks including high density, poor chemical stability, and high loading content. By contrast, carbonaceous materials are believed to be another promising MA candidates, owing to their lightweight, favorable physicochemistry stability, and tunable dielectric loss, which have attracted both industrial and academic interests.12-14 Recently, vast advances in MA theory and fabrication technology have demonstrated that the porous structure brings about considerable enhancement in the MA performance. The nano-scale pores will not induce the scattering of incident microwave and thus act as “effective medium” to 2 ACS Paragon Plus Environment

Page 3 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


satisfy impedance matching.15-17 The presence of micro-scale pores can act as dihedral angles for the microwave reflection. The microwave reflects many times among the dihedral angles, which increases the propagation path of microwave in the absorber and leads to the loss of electromagnetic energy.18, 19 By right of superimposed positive effects of multi-scale pores, hierarchically porous structure will significantly contribute to the MA performance. For example, the MA performance of activated carbon with micro-scale porous structure was proved to be much better than that of most carbonaceous materials with uniform pores.20 In addition, it was found that carbon hollow microspheres with mesopores could achieve a maximum reflection loss (RL) of -84 dB, almost four times as high as that of carbon hollow microspheres without mesopores and nine times higher than that of compacted carbon microspheres.21 Inspired by the concept, more and more hierarchically porous carbons (HPCs) for MA applications are now designed on the basis of the synergism between composition and structure. Extensively used strategies for the generation of hierarchically porous structure involve templating approaches and etching methods.22, 23 However, these processes severely suffer from expensive raw materials and environmentally hazardous preparation technologies. The biomasses possess naturally micro-scale porous vascular bundles that can work as paths for water and ion transport. Additionally, these biomasses also contain various alkaline metal elements, promoting the photosynthesis, metabolism and translocation of carbohydrates, and synthesis of protein. Therefore, not only can the inherent micro-scale porous structure be well 3 ACS Paragon Plus Environment


Page 4 of 29

preserved without templates after carbonization process, but also the embedded alkaline metal elements can activate the biomass-derived carbon in suit through etching reaction without the need of external activator, producing abundant microporous structure. Thus HPCs with high specific surface areas are formed.24, 25 In comparison with the widely used template and etching strategies, the template-free technique is an environmental friendly and sustainable choice, which is hardly applied for the MA material preparation to our best knowledge. Herein, we reported a variety of biomass-derived HPCs prepared via the one-step carbonization process and the investigation of their MA performance. By adjusting the carbonization temperature and absorbent loading in the paraffin matrix, the obtained HPCs achieve the maximum MA capacity with a RL value of as much as -62.2 dB and a broad effective absorption bandwidth (EAB) of 7.3 GHz. Particularly, the excellent MA performance can be reproduced using the same kind of biomass with different harvested seasons and origins. In addition, the MA performance of HPCs templating from different biomasses is also estimated, which is superior to those of most of reported carbonaceous materials. Detailed investigation reveals that high conduction loss originated from components together with multi-reflection of microwave and strong interfacial polarization promoted by structure results in such remarkable MA performance. These achievements light the way to large-scale preparation of excellent MA absorbents utilizing the biomasses as precursors. EXPERIMENTAL SECTION

4 ACS Paragon Plus Environment

Page 5 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Preparation of biomass-derived HPCs. Spinach stem was cleaned, dried, and finally heated at 600 °C for 2 h with a heating rate of 5 °C/min. The resulting sample was washed with distilled water until the filtrate appeared neutral. After being dried under vacuum, the final product was obtained and named HPC-S. For comparison, the samples were carbonized at 500, 700, and 800 °C, respectively. In addition, two kinds of spinach stem bought in different seasons were also used to prepare the HPCs. The other HPCs starting from different biomass precursors were prepared with the same procedures. Microwave absorption measurements. The test sample was prepared by pressing the homogeneous HPCs/paraffin mixture into a toroidal-shaped pipe with an outer diameter of 7.0 mm and an inner diameter of 3.0 mm. The loadings of HPC-S in test samples were 20, 30, and 40 wt%, respectively. The electromagnetic parameters were measured by an Agilent N5222A vector network analyser using the coaxial-line method. Subsequently, the relative complex permeability ( = − ′′ ) and permeability ( = − ′′) in the frequency range of 2-18 GHz could be obtained. The RL values were calculated based on the transmission line theory: = ⁄ ℎ−(2 ⁄) () = −20 | − 1⁄ + 1|

where f represents the frequency, c means the velocity of light, d is the thickness, and refers to the normalized input impedance of a metal-backed microwave absorbing layer. Detail preparation process of the test sample is schematically shown in Scheme S1. 5 ACS Paragon Plus Environment


Page 6 of 29

Characterization. The morphology was observed by scanning electron microscope (SEM, Hitachi SU-70). The X-ray diffraction (XRD) patterns were carried out on a Bruker-Axe x-ray diffractometer with Cu Kα radiation source (40.0 kV, 40.0 mA). The Raman spectra were obtained on a Renishaw inVia spectrometer using laser excitation at 532 nm. Elemental analysis was recorded using CHNOS Elemental Analyzer Vario EL III (Elementar Analysensysteme GmbH, Germany). N2 adsorption/desorption isotherms were measured at 77 K using a Micromeritics TriStar II 3020 static volumetric analyzer. The Brunauer-Emmett-Teller (BET) surface area was calculated within the relative pressure range of 0.05 to 0.20. Pore size distribution was deduced from the absorption isotherms by nonlocal density functional theory.26 The mercury intrusion porosimetry measurement was carried out using a MicroActive Autopore V 9600 porosimeter. Sample was subjected to a pressure cycle starting at approximately 0.49 psi, increasing to 60,000 psi in predefined steps, and the pore size is calculated on the basis of Washborn-Laplace equation: $ = −4& cos *⁄, where P is the pressure, d is the diameter of the pore, & and * are the surface tension and contact angle of the liquid, respectively.27 Conductivity of the samples was determined using a RTS-9 four-point probe instrument. Sample was pressured into sheet before test, and the sheet resistivity was calculated by measuring the potential difference between the two inner points at a given current. RESULTS AND DISCUSSION


Page 7 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1. Digital photos of spinach stem harvested in January, 2017, HPC-S, and the test sample (a); RL curves of the test sample with 30 wt% HPC-S carbonized at 600 °C (b); the comparison of the optimal MA performance of HPC-S with those of the representative carbonaceous materials reported previously (c).

The spinach, a common plant, was selected as the precursor for investigating the MA performance of biomass-derived HPCs (Figure 1a). The additive-free HPC-S was prepared by directly carbonizing spinach stem, followed by washing and drying treatment. Twelve test samples (absorbent/paraffin composite) were fabricated in accordance with the established experimental program, which was combinations of four carbonization temperatures ranging from 500 to 800 °C and three filler loadings of absorbent ranging from 20 to 40 wt% (Figure S1). Among them, the sample with 30 wt% HPC-S that is carbonized at 600 °C exhibits the optimal MA performance. The maximum value of RL (RLmax) attains as much as -62.2 dB at 12.5 GHz with a thickness of 2.71 mm, while the EAB is up to 7.3 GHz, which is almost a half the frequency band of 2.0–18.0 GHz (Figure 1b). To our best knowledge, these values are superior to those of most MA materials reported previously, as summarized in Figure



1c.19-21,

28-34

Page 8 of 29

With such outstanding MA performance, the HPC-S can be applied

widely in anti-electromagnetic radiation textiles and the radar absorbing coatings. The mechanisms behind the impressive MA performance are described as follows.

Figure 2. SEM figures of dried (a) and carbonized (b) spinach stem; the pore size distribution obtained by mercury intrusion porosimetry (c), and the N2 absorption-desorption isotherm (d) of HPC-S carbonized at 600 °C.

As shown in Figure 2a, pristine spinach stem is mainly made of the epidermis protecting inside tissues and the vascular bundles conducting water and inorganic salts. After carbonization, the obtained carbon material principally inherits the porous structure with pore size ranging from 2 to 30 µm (Figure 2b and Figure S2). The statistical micro-scale pore size distribution and porosity are characterized by mercury intrusion porosimetry (Figure 2c). The microstructure of HPC-S is further explored by N2 adsorption/desorption experiment performed at 77 K. The isotherm curve exhibits a rapid N2 uptake at a very low pressure region (P/P0 < 0.01), followed by a continuous increase in

the rest of P/P0 range and

a mesopore-caused

adsorption-desorption hysteresis loop (Figure 2d), indicative of the presence of 8 ACS Paragon Plus Environment

Page 9 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


micro-/meso-/macro pores,35 as plotted in the Figure S3. The large micropore volume of 0.16 cm3 g-1 and high specific surface area of 345.3 m2 g-1 are believed to be produced by alkaline metal element activation process. In comparison with KOH activated biomass materials, the HPCs in our case are obtained without external activator, suggesting a green carbonization process. Thanks to the superimposed effects of both nano and micro-scale pores, hierarchically porous structure contributes to the MA performance of the biomass-based HPCs. The micro-sized cavities will act as dihedral angles to promote the reflection of microwave inside the absorber and lead to the loss of electromagnetic energy by increasing the propagation path of microwave (Figure S4).18, 19 It is well known that an incident wave is not sensitive to the particles and structure that are smaller than a sensing wavelength, thus the nano-sized pores can work as an “effective medium”.15 The effective permittivity of HPC-S can be calculated using Maxwell-Garnet model:

(20 + 1 ) + 22(1 − 0 ) -. +,, =/ 3 (20 + 1 ) − 2(1 − 0 ) 0 where 0 and 1 are the permittivity of matrix material and air in the pores, respectively, and 2 represents the volume fraction of the pore.16, 17, 36 The larger the volume of air is, the lower the value of effective permittivity is, because the value of permittivity of dielectric matrix is much higher than that of air. Therefore, the presence of nano-sized pores in HPC-S can decrease the permittivity and optimize the

4 matching, as explained in the following. It is well known that the closer the values of characteristic impedance ( 4 = 5 ⁄5 ⁄ ) of absorbent are to 1 (the

values of air’s 4 ), the more the microwave can propagate into the absorbent, which 9 ACS Paragon Plus Environment


Page 10 of 29

also means more matched 4 .28 For the carbonaceous material, the values of are much lower than those of in the microwave frequency. Therefore, the decrease in the values of leads to the increase in the values of ⁄ , which makes the

values of 4 closer to 1.

Figure 3. The dependence of carbonization temperature on XRD patterns (a), Raman spectra (b), elemental components (c), real (d) and imaginary (e) parts of the complex permittivity, dielectric loss tangent and characteristic impedance (f), and RL curves (g to i) of HPC-S when the absorbent loading is 30 wt%. The RL curves of HPC-S carbonized at 600 °C are shown in Figure 1b.


Page 11 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In addition, the chemical composition (degree of graphitization) of HPC-S can also be adjusted by carbonization temperature, in order to obtain the optimal MA performance collocating hierarchically porous structure. As shown in Figure 3a, two broad diffraction peaks centered at 24.3° and 43.3° can be observed in all patterns, indicating the formation of graphitic carbon, albeit with disorder.37 The Raman spectra of HPC-Ses obtained at different carbonization temperatures are shown in Figure 3b. All the samples display two peaks at 1351 cm-1 and 1590 cm-1, corresponding to the D and G bands, respectively.38 The integrated intensity ratio of D and G bands (ID/IG) increases from 0.91 to 0.99 with raising the annealing temperature from 500 to 700 °C. According to the phenomenological three-stage model proposed by Ferrari and Roberston, the gradually increased ID/IG value of HPC-S is exactly in the transitional stage from amorphous carbon to nanocrystalline graphite.39 When increasing carbonization temperature to 800 °C, the ID/IG value reduces to 0.96 because of the enlarged sp2 carbon domain, demonstrating the transformation from nanocrystalline graphite to graphite. The dependence of carbonization temperature on elemental components of HPC-Ses is shown in Figure 3c. The carbon content grows continuously with the increase of carbonization temperature. While the tendency is opposite for the oxygen and nitrogen contents, suggesting the decrease of defects.40 Moreover, free conduction electrons will appear in great numbers at the time when the carbonization temperature is high enough to drive most of the heteroatoms out of the carbon, which in conjunction with a gradual replacement of the high opaque



Page 12 of 29

intermolecular barriers by low resistance C─C contacts (enlarged nanocrystalline graphite domain) leads to the enhancement in conductivity.41 The complex permittivity plots of HPC-Ses carbonized at different temperatures are collected in Figure 3d and e for comparison. It is evident that both the values of and increase with the increasing of carbonization temperature, which may be explained as following. Four kinds of polarization including electronic, atomic, Debye (dipolar) and interfacial polarization can exist in a heterogeneous system.42 Usually, the former two kinds occur at higher frequencies,43 which can be excluded from the following discussion. On the basis of Debye polarization theory,44 the complex permittivity can be deduced as 6 −

7 + 8 1 5 − 8 1 9 + (ε′′)1 = ( ) 2 2

where 5 is the dielectric constant in vacuum, 7 is the static permittivity and 8 is relative dielectric permittivity at the high-frequency limit. When the plot of ε′′ versus (Cole-Cole plot) is a semicircle, it represents one Debye relaxation process.45 In our case, the Cole-Cole plots of these four samples only demonstrate slight fluctuations and have no evident Debye peak (Figure S5), suggesting that dipolar polarization is negligible while interfacial polarization may play a major role during polarization process. This result is consistance with the previous report that denied the existence of dipolar polarization in biomass-derived carbons carbonized above 500 °C.46 Usually, the interfacial polarization is caused by the aggregation of carriers at the interfaces.47 The increment of carbonization temperature facilitates not only the enlargement of specific surface area of HPC-S (Figure S6), but also the 12 ACS Paragon Plus Environment

Page 13 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


generation of free electrons. Eventually, the increase of values of may be the result of the enhanced interfacial polarization caused by more massive accumulation of electrons at larger interfaces; the increase of values of may arise from enhanced polarization loss and conduction loss induced by increased conductivity (Figure S7). The dependence of frequency on the complex permeability of HPC-S is shown in Figure S8. Despite with slight fluctuations, it can be found that the values of and are close to 1 and 0, respectively, suggesting the negligible magnetic loss. The fluctuations are thought to be induced by the micro-sized pores, as explained in the following. The micro-porous structure can cause the scattering of local electric field. As the electric and magnetic fields are mutually concomitant EM wave propagation, the direction of magnetic field will change when an electric field changes its direction. The varying magnitude and direction of magnetic field will induce electric currents on conductive circular paths according to Lenz’s law. The flowing currents decay in the micro-scale porous structure by converting into heat, resulting in partial energy attenuation of the scattered magnetic fields.48 Attenuation ability (dielectric loss for carbonaceous material, tan > = ⁄ ) and characteristic impedance ( 4 ) are two main factors that determine the MA capacity. Majority of microwave can enter into the absorbent when the 4 is well matched with that of the air, and the incident microwave can be dissipated as much as possible when the absorbent has strong attenuation ability.49 The values of tan > and 4 of HPC-Ses carbonized at different carbonization temperatures were measured and plotted in Figure 3f. With the increasing of carbonization temperature, the values of 13 ACS Paragon Plus Environment


Page 14 of 29

tan > evidently increase while the values of 4 decrease, suggesting the enhanced dielectric loss and mismatched 4 . On the basis of the balance between tan > and 4 , HPC-S carbonized at 600 °C demonstrates the optimum MA performance. Moreover, it can be found that dried spinach stem exhibits poor MA performance because of the negligible dielectric loss (Figure S9), highlighting the importance of carbonization process.

Figure 4. The dependence of filler loading on the complex permittivity (a and b), dielectric loss tangent and characteristic impedance (c), and RL (d and e) of HPC-S/paraffin composites when the carbonization temperature of HPC-S is 600 °C. The RL curves of composite with 30 wt% HPC-S are shown in Figure 1b.

In addition to the carbonization temperature, another parameter, the absorbent loading in paraffin, also has significant influence on the MA performance.50 The correlation between the complex permittivity of as-prepared HPC-S/paraffin composite and different absorbent loading is shown in Figure 4a and b when the 14 ACS Paragon Plus Environment

Page 15 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


carbonization temperature of HPC-S is 600 °C. Since the values of ε′ of paraffin are close to those of the air (Figure S10), the values of ε′ of the test samples increase along with the HPC-S content, according to the effective medium theory.44 The similar tendency of the values of ε′′ versus absorbent loading can be ascribed that the aggregation of HPC-S particles enhances the conduction loss. According to the aggregation-induced charge transport mechanism and conducting network model proposed by Cao et al,44,

51, 52

migrating electrons move directionally or hopping

electrons jump across the interfaces between absorbent particles respectively, when the microwave propagates into the composites. Higher absorbent content leads to a decrease in the energy barrier for hopping electrons and causes a dense micro-current interconnected network (Figure S11), which promotes the conduction loss of the test samples. The dependence of HPC-S loading on tan > and 4 of test sample is shown in Figure 4c, respectively. Similarly, the values of tan > increase with the increasing absorbent loading while the values of 4 decrease, indicating the enhancement of dielectric loss and mismatching of 4 . The optimum MA capacity can be obtained by tuning the the absorbent loading to achieve the best match between tan > and 4 . Eventually, the best MA performance is obtained when using a 30 wt% absorbent loading (Figure 1b). With the guidance of above results, the other biomass-derived carbonaceous materials with excellent MA performance can be obtained according to the following criterions. First, biomass precursors with abundant micro-sized porous structure and the embedded alkaline metal elements are essential. Second, the optimal match 15 ACS Paragon Plus Environment


Page 16 of 29

between tan > and 4 can be achieved by adjusting carbonization temperature and filler loading of absorbent.

Figure 5. The dependence of the frequency on the complex permittivity (a) and RL of HPCs prepared using spinach stems harvested in July, 2016 (b) and in July, 2017 (c), respectively.

The reproducibility of the MA performance of biomass-based HPCs is confirmed using spinach stems harvested in different seasons (July 2016 and July 2017, respectively) and at different origins. As shown in Figure S12, the harvest season and origin hardly have affection to the hierarchical characteristic of the HPC. By adjusting carbonization temperature and absorbent loading, HPCs templating from these spinach stems achieve the similar complex permittivity and MA performance. Table 1. The MA performance of HPCs derived from different biomass precursors. Precursor

Organ Tc

(Family)

FL

RLmax

EAB

Thickness

(°C)a

(wt%)b

(dB)

(GHz)

(mm)

Pakchoi

stem

600

50

-51.5

5.1

2.15

(Brassicaceae)

leaf

600

30

-53.6

4.8

2.10

Cabbage

stem

700

50

-52.8

5.1

2.52

(Brassicaceae)

leaf

600

30

-41.4

5.1

2.40


Page 17 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Celery stem

600

30

-51.7

1.5

4.64

/

600

30

-25.6

6.6

2.20

stem

600

30

-62.2

7.3

2.71

700

30

-41.2

4.6

1.50

600

50

-22.6

7.8

2.50

(Apiaceae) Kelp (Laminariaceae)

Spinach stem (Chenopodiaceae) leaf a

Carbonization temperature; b filler loading of absorbent.

The other four kinds of biomasses, including pakchoi (Brassicaceae), cabbage (Brassicaceae), celery (Apiaceae), kelp (Laminariaceae) were chosen to investigate the influence of family difference on the biomass-derived MA materials. After the same washing, drying and carbonization process, all the biomass-derived HCPs demonstrate the hierarchically porous structure and high porosity (Figure S13). Their MA performance is measured and summarized in Table 1. It is found that the MA performance of these absorbents are superior to those of most carbonaceous absorbents reported previously though they are classified as different families. For instance, the HPCs derived from the stems of pakchoi and cabbage have the RLmax over -50 dB and the EAB wider than 5.0 GHz; the HPC derived from the spinach leaf exhibits an ultra-wide EAB of 7.8 GHz with the thickness of 2.50 mm. These facts reveal that the MA performance of biomass-based HPCs is predominantly by their porous structure and chemical composition.

CONCLUSION 17 ACS Paragon Plus Environment


Page 18 of 29

In conclusion, a new kind of biomass-based MA materials has been successfully prepared using biomasses belonging to different families. Templating from the inherently their micro-scale porous tissue structure and activated by the embedded alkaline metal elements, carbon materials with hierarchically porous structure and high surface areas are formed after one-step carbonization process without the need of external activator. The obtained HPCs demonstrate excellent MA performance superior to those of most carbonaceous absorbents reported previously. Such outstanding MA performance results from the strong conduction loss, interfacial polarization and multiple reflections of microwave induced by highly conductivity components and hierarchically porous structure. The detailed investigation also indicates that the harvesting seasons and origins have no influence on the MA performance of the biomass-based HPCs. These accomplishments indicate the promising MA application values of the green and sustainable biomass-based HPCs. Furthermore, it is believed that the investigation on the hierarchically porous structure in this work provides new inspirations and insights for the preparation of novel porous microwave absorbents with the stronger reflection loss in the wider frequency band. ASSOCIATED CONTENT

Supporting Information.

SEM images and Cole-Cole plots of HPC-S; SEM images, N2 absorption-desorption isotherms, and RL curves of other biomass-derived HPCs; complex permittivity and RL curves of paraffin and dried spinach; the dependence of carbonization temperature 18 ACS Paragon Plus Environment

Page 19 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


on the conductivity and complex permeability of HPC-S, RL curves of HPCs; schematic models of conductive networks and multiple reflections of microwave; the schematic illustration of experimental conditions. These materials are available free of charge via the Internet at http://pubs.acs.org

AUTHOR INFORMATION Corresponding Author *Tel: +86-592-2186296. Fax: +86-592-2183937. E-mail: [email protected].

Author Contributions All authors contributed to the experimental design and data analyses. The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Notes The authors declare no competing financial interest.

ACKNOWLEDGMENT

This work was supported by the National Natural Science Foundation of China (Nos. 51373143 and 21674087) and the Natural Science Foundation of Fujian Province (No. 2014J07002).

REFERENCES



1.

Page 20 of 29

Wen, B.; Cao, M. S.; Lu, M. M.; Cao, W. Q.; Shi, H. L.; Liu, J.; Wang, X. X.;

Jin, H. B.; Fang, X. Y.; Wang, W. Z.; Yuan, J. Reduced Graphene Oxides: Light-Weight and High-Efficiency Electromagnetic Interference Shielding at Elevated Temperatures. Adv. Mater. 2014, 26, 3484-3489.

2.

Che, R. C.; Peng, L. M.; Duan, X. F.; Chen, Q.; Liang, X. L. Microwave

Absorption Enhancement and Complex Permittivity and Permeability of Fe Encapsulated within Carbon Nanotubes. Adv. Mater. 2004, 16, 401-405.

3.

Liu, Q. H.; Cao, Q.; Bi, H.; Liang, C. Y.; Yuan, K. P.; She, W.; Yang, Y. J.; Che,

R. C. CoNi@SiO2@TiO2 and CoNi@Air@TiO2 Microspheres with Strong Wideband Microwave Absorption. Adv. Mater. 2016, 28, 486-490.

4.

Wang, X. X.; Ma, T.; Shu, J. C.; Cao, M. S. Confinedly Tailoring Fe3O4

Clusters-NG to Tune Electromagnetic Parameters and Microwave Absorption with Broadened Bandwidth. Chem. Eng. J. 2018, 332, 321-330.

5.

Wu, Z. C.; Tan, D. G.; Tian, K.; Hu, W.; Wang. J. J.; Su, M. X. Li, L. Facile

Preparation

of

Core−Shell

Fe3O4@Polypyrrole

Composites

with

Superior

Electromagnetic Wave Absorption Properties. J. Phys. Chem. C 2017, 121, 15784-15792

6.

Du, Y. C.; Liu, W. W.; Qiang, R.; Wang, Y.; Han, X. J.; Ma, J.; Xu, P. Shell

Thickness-Dependent Microwave Absorption of Core-Shell Fe3O4@C Composites. ACS Appl. Mater. Interfaces 2014, 6, 12997-13006.


Page 21 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


7.

Jian, X.; Wu, B.; Wei, Y. F.; Dou, S. X.; Wang, X. L.; He, W. D.; Mahmood, N.

Facile Synthesis of Fe3O4/GCs Composites and Their Enhanced Microwave Absorption Properties. ACS Appl. Mater. Interfaces 2016, 8, 6101-6109.

8.

Lu, Y. Y.; Wang, Y. T.; Li, H. L.; Lin, Y.; Jiang, Z. Y.; Xie, Z. X.; Kuang, Q.;

Zheng, L. S. MOF-Derived Porous Co/C Nanocomposites with Excellent Electromagnetic Wave Absorption Properties. ACS Appl. Mater. Interfaces 2015, 7, 13604-13611.

9.

Yang, H. J.; Cao, W. Q.; Zhang, D. Q.; Su, T. J.; Shi, H. L.; Wang, W. Z.; Yuan,

J.; Cao, M. S. NiO Hierarchical Nanorings on SiC: Enhancing Relaxation to Tune Microwave Absorption at Elevated Temperature. ACS Appl. Mater. Interfaces 2015, 7, 7073-7077.

10. Lu, M. M.; Cao, M. S.; Chen, Y. H.; Cao, W. Q.; Liu, J.; Shi, H. L.; Zhang, D. Q.; Wang, W. Z.; Yuan, J. Multiscale Assembly of Grape-Like Ferroferric Oxide and Carbon Nanotubes: A Smart Absorber Prototype Varying Temperature to Tune Intensities. ACS Appl. Mater. Interfaces 2015, 7, 19408-19415.

11. Liu, J.; Cao, M. S.; Luo, Q.; Shi, H. L.; Wang, W. Z.; Yuan, J. Electromagnetic Property and Tunable Microwave Absorption of 3D Nets from Nickel Chains at Elevated Temperature. ACS Appl. Mater. Interfaces 2016, 8, 22615-22622.

12. Zhang, Y.; Huang, Y.; Zhang, T. F.; Chang, H. C.; Xiao, P. S.; Chen, H. H.; Huang, Z. Y.; Chen, Y. S. Broadband and Tunable High-Performance Microwave



Page 22 of 29

Absorption of an Ultralight and Highly Compressible Graphene Foam. Adv. Mater. 2015, 27, 2049-2053.

13. Wang, G. Z.; Gao, Z.; Tang, S. W.; Chen, C. Q.; Duan, F. F.; Zhao, S. C.; Lin, S. W.; Feng, Y. H.; Zhou, L.; Qin, Y. Microwave Absorption Properties of Carbon Nanocoils Coated with Highly Controlled Magnetic Materials by Atomic Layer Deposition. ACS Nano 2012, 6, 11009-11017.

14. Cao, W. Q.; Wang, X. X.; Yuan, J.; Wang, W. Z.; Cao, M. S. Temperature Dependent Microwave Absorption of Ultrathin Graphene Composites. J. Mater. Chem. C 2015, 3, 10017-10022.

15. Quan, B.; Liang, X. H.; Ji, G. B.; Zhang, Y. A.; Xu, G. Y.; Du, Y. W. Cross-Linking-Derived Synthesis of Porous CoxNiy/C Nanocomposites for Excellent Electromagnetic Behaviors. ACS Appl. Mater. Interfaces 2017, 9, 38814-38823.

16. Wing, Z. N.; Wang, B.; Halloran, J. W. Permittivity of Porous Titanate Dielectrics. J. Am. Ceram. Soc. 2006, 89, 3696-3700.

17. Garnett, J. C. M. Colours in Metal Glasses, in Metallic Films, and in Metallic Solutions. II. Philos. Trans. R. Soc. London Ser. A 1906, 205, 237-288.

18. Fan, Y. X.; Yang, H. B.; Li, M. H.; Zou, G. T. Evaluation of the Microwave Absorption Property of Flake Graphite. Mate. Chem. Phys. 2009, 115, 696-698.


Page 23 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


19. Li, G.; Xie, T. S.; Yang, S. L.; Jin, J. H.; Jiang, J. M. Microwave Absorption Enhancement of Porous Carbon Fibers Compared with Carbon Nanofibers. J. Phys. Chem. C 2012, 116, 9196-9201.

20. Qiu, X.; Wang, L. X.; Zhu, H. L.; Guan, Y. K.; Zhang, Q. T. Lightweight and Efficient Microwave Absorbing Materials Based on Walnut Shell-Derived Nano-Porous Carbon. Nanoscale 2017, 9, 7408-7418.

21. Xu, H. L.; Yin, X. W.; Zhu, M.; Han, M. K.; Hou, Z. X.; Li, X. L.; Zhang, L. T.; Cheng, L. F. Carbon Hollow Microspheres with a Designable Mesoporous Shell for High-Performance Electromagnetic Wave Absorption. ACS Appl. Mater. Interfaces 2017, 9, 6332-6341.

22. Deng, Y. H.; Liu, C.; Yu, T.; Liu, F.; Zhang, F. Q.; Wan, Y.; Zhang, L. J.; Wang, C. C.; Tu, B.; Webley, P. A.; Wang, H. T.; Zhao, D. Y. Facile Synthesis of Hierarchically Porous Carbons from Dual Colloidal Crystal/Block Copolymer Template Approach. Chem. Mater. 2007, 19, 3271-3277.

23. Joo, S. H.; Choi, S. J.; Oh, I.; Kwak, J.; Liu, Z.; Terasaki, O.; Ryoo, R. Ordered Nanoporous Arrays of Carbon Supporting High Dispersions of Platinum Nanoparticles. Nature 2001, 412, 169-172.

24. Zhang, Y.; Liu, S. S.; Zheng, X. Y.; Wang, X.; Xu, Y.; Tang, H. Q.; Kang, F. Y.; Yang, Q. H.; Luo, J. Y. Biomass Organs Control the Porosity of Their Pyrolyzed Carbon. Adv. Funct. Mater. 2017, 27, 1604687.



Page 24 of 29

25. Biswal, M.; Banerjee, A.; Deo, M.; Ogale, S. From Dead Leaves to High Energy Density Supercapacitors. Energy Environ. Sci. 2013, 6, 1249-1259.

26. Lastoskie, C.; Gubbins, K. E.; Quirke, N. Pore Size Distribution Analysis of Microporous Carbons: A Density Functional Theory Approach. J. Phys. Chem. 1993, 97, 4786-4796.

27. Abell, A. B.; Willis, K. L.; Lange, D. A. Mercury Intrusion Porosimetry and Image Analysis of Cement-Based Materials. J. Colloid Interf. Sci. 1999, 211, 39-44.

28. Pan, H. X.; Yin, X. W.; Xue, J. M.; Cheng, L. F.; Zhang, L. T. In-Situ Synthesis of Hierarchically Porous and Polycrystalline Carbon Nanowires with Excellent Microwave Absorption Performance. Carbon 2016, 107, 36-45.

29. Qiang, R.; Du, Y. C.; Wang, Y.; Wang, N.; Tian, C. H.; Ma, J.; Xu, P.; Han, X. J. Rational Design of Yolk-Shell C@C Microspheres for the Effective Enhancement in Microwave Absorption. Carbon 2016, 98, 599-606.

30. Wen, F. S.; Hou, H.; Xiang, J. Y.; Zhang, X. Y.; Su, Z. B.; Yuan, S. J.; Liu, Z. Y. Fabrication of Carbon Encapsulated Co3O4 Nanoparticles Embedded in Porous Graphitic Carbon Nanosheets for Microwave Absorber. Carbon 2015, 89, 372-377.

31. Yuan, K. P.; Che, R. C.; Cao, Q.; Sun, Z. K.; Yue, Q.; Deng, Y. H. Designed Fabrication and Characterization of Three-Dimensionally Ordered Arrays of Core-Shell Magnetic Mesoporous Carbon Microspheres. ACS Appl. Mater. Interfaces 2015, 7, 5312-5319. 24 ACS Paragon Plus Environment

Page 25 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


32. Zhang, X. M.; Ji, G. B.; Liu, W.; Quan, B.; Liang, X. H.; Shang, C. M.; Cheng, Y.; Du, Y. W. Thermal Conversion of an Fe3O4@Metal-Organic Framework: A New Method for an Efficient Fe-Co/Nanoporous Carbon Microwave Absorbing Material. Nanoscale 2015, 7, 12932-12942.

33. Zhou, H.; Wang, J. C.; Zhuang, J. D.; Liu, Q. A Covalent Route for Efficient Surface Modification of Ordered Mesoporous Carbon as High Performance Microwave Absorbers. Nanoscale 2013, 5, 12502-12511.

34. Fang, J. Y.; Liu, T.; Chen, Z.; Wang, Y.; Wei, W.; Yue, X. G.; Jiang, Z. H. A Wormhole-Like Porous Carbon/Magnetic Particles Composite as an Efficient Broadband Electromagnetic Wave Absorber. Nanoscale 2016, 8, 8907-8917.

35. Gao, H.; Ding, L.; Bai, H.; Liu, A. H.; Li, S. Z.; Li, L. Pitch-Based Hyper-Cross-Linked Polymers with High Performance for Gas Adsorption. J. Mater. Chem. A 2016, 4, 16490-16498.

36. Du, Y. C.; Liu, T.; Yu, B.; Gao, H. B.; Xu, P.; Wang, J. Y.; Wang, X. H.; Han, X. J. The Electromagnetic Properties and Microwave Absorption of Mesoporous Carbon. Mater. Chem. Phys. 2012, 135, 884-891.

37. Guo, C. Z.; Liao, W. L.; Li, Z. B.; Chen, C. G. Exploration of the Catalytically Active Site Structures of Animal Biomass-Modified on Cheap Carbon Nanospheres for Oxygen Reduction Reaction with High Activity, Stability and Methanol-Tolerant Performance in Alkaline Medium. Carbon 2015, 85, 279-288.



Page 26 of 29

38. Qie, L.; Chen, W. M.; Wang, Z. H.; Shao, Q. G.; Li, X.; Yuan, L. X.; Hu, X. L.; Zhang, W. X.; Huang, Y. H. Nitrogen-Doped Porous Carbon Nanofiber Webs as Anodes for Lithium Ion Batteries with a Superhigh Capacity and Rate Capability. Adv. Mater. 2012, 24, 2047-2050.

39. Nemanich, R. J.; Solin, S. A. First- and Second-Order Raman Scattering from Finite-Size Crystals of Graphite. Phys. Rev. B 1979, 20, 392-401.

40. Zhang, Y.; Huang, Y.; Chen, H. H.; Huang, Z. Y.; Yang, Y.; Xiao, P. S.; Zhou, Y.; Chen, Y. S. Composition and Structure Control of Ultralight Graphene Foam for High-Performance Microwave Absorption. Carbon 2016, 105, 438-447.

41. Mrozowski, S. Semiconductivity and Diamagnetism of Polycrystalline Graphite and Condensed Ring Systems. Physical Review 1952, 85, 609-620.

42. Watts, P. C. P.; Hsu, W. K.; Barnes, A.; Chambers, B. High Permittivity from Defective Multiwalled Carbon Nanotubes in the X-Band. Adv. Mater. 2003, 15, 600-603.

43. Chen, Y. J.; Gao, P.; Zhu, C. L.; Wang, R. X.; Wang, L. J.; Cao, M. S.; Fang, X. Y. Synthesis, Magnetic and Electromagnetic Wave Absorption Properties of Porous Fe3O4/Fe/SiO2 Core/Shell Nanorods. J. Appl. Phys. 2009, 106, 054303. 44. Wen, B.; Cao, M. S.; Hou, Z. L.; Song, W. L.; Zhang, L.; Lu, M. M.; Jin, H. B.; Fang, X. Y.; Wang, W. Z.; Yuan, J. Temperature Dependent Microwave Attenuation Behavior for Carbon-Nanotube/Silica Composites. Carbon 2013, 65, 124-139. 26 ACS Paragon Plus Environment

Page 27 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


45. He, J. Z.; Wang, X. X.; Zhang, Y. L.; Cao, M. S. Small Magnetic Nanoparticles Decorating Reduced Graphene Oxides to Tune the Electromagnetic Attenuation Capacity. J. Mater. Chem. C 2016, 4, 7130-7140.

46. Sugimoto, H.; Norimoto, M. Dielectric Relaxation Due to Interfacial Polarization for Heat-Treated Wood. Carbon 2004, 42, 211-218.

47. Tsangaris, G. M.; Psarras, G. C.; Kouloumbi, N. Electric Modulus and Interfacial Polarization in Composite Polymeric Systems. J. Mater. Sci. 1998, 33, 2027-2037.

48. Fang, Z. G.; Li, C. S.; Sun, J. Y.; Zhang, H. T.; Zhang, J. S. The Electromagnetic Characteristics of Carbon Foams. Carbon 2007, 45, 2873-2879.

49. Tian, C. H.; Du, Y. C.; Xu, P.; Qiang, R.; Wang, Y.; Ding, D.; Xue, J. L.; Ma, J.; Zhao, H. T.; Han, X. J. Constructing Uniform Core-Shell PPy@PANI Composites with Tunable Shell Thickness toward Enhancement in Microwave Absorption. ACS Appl. Mater. Interfaces 2015, 7, 20090-20099.

50. Song, W. L.; Cao, M. S.; Fan, L. Z.; Lu, M. M.; Li, Y.; Wang, C. Y.; Ju, H. F. Highly Ordered Porous Carbon/Wax Composites for Effective Electromagnetic Attenuation and Shielding. Carbon 2014, 77, 130-142.

51. Song, W. L.; Cao, M. S.; Hou, Z. L.; Fang, X. Y.; Shi, X. L.; Yuan, J. High Dielectric Loss and Its Monotonic Dependence of Conducting-Dominated Multiwalled Carbon Nanotubes/Silica Nanocomposite on Temperature Ranging from 373 to 873 K in X-Band. Appl. Phys. Lett. 2009, 94, 233110. 27 ACS Paragon Plus Environment


Page 28 of 29

52. Cao, M. S.; Song, W. L.; Hou, Z. L.; Wen, B.; Yuan, J. The Effects of Temperature and Frequency on the Dielectric Properties, Electromagnetic Interference Shielding and Microwave-Absorption of Short Carbon Fiber/Silica Composites. Carbon 2010, 48, 788-796.


Page 29 of 29 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


TOC Figure


Hierarchically Porous Carbons Derived from Biomasses with Excellent

Recommend Documents