Preparation of hundred-micron carbon spheres using solvent extraction in a simple microchannel device

Carbon microspheres with a uniform size of about 170 μm were prepared in a simple co-flow microfluidic device using solvent extraction method. An ethanol solution of colloidal silica and phenol formaldehyde (PF) resol was used as the dispersion phase, and a mixture of hexane and diisopropylamine was used as the continuous phase. The droplets of PF resol resin/silica were generated in the continuous phase.

Available online 20 August 2022

1387-1811/© 2022 The Authors Published by Elsevier Inc This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/)

Preparation of hundred-micron carbon spheres using solvent extraction in a

simple microchannel device

aState Key Laboratory of Materials-Oriented Chemical Engineering, College of Chemistry and Chemical Engineering, Nanjing Tech University, Nanjing, 211816, China

bChemical Technology, Luleå University of Technology, SE-971 87, Luleå, Sweden

A R T I C L E I N F O

Keywords:

Hundred-micron carbon spheres

Porous carbon microspheres

Solvent extraction

Microfluidics

Phenol phenolic resin

A B S T R A C T Carbon microspheres with a uniform size of about 170 μm were prepared in a simple co-flow microfluidic device using solvent extraction method An ethanol solution of colloidal silica and phenol formaldehyde (PF) resol was used as the dispersion phase, and a mixture of hexane and diisopropylamine was used as the continuous phase The droplets of PF resol resin/silica were generated in the continuous phase Colloidal silica assisted the for-mation of the spherical structure and worked as a pore generator The continuous phase was also used as extractant and catalyst for PF resin/silica microspheres formation Curing, drying, carbonization and leaching were used for the post-treatment of the PF resin/silica microspheres to obtain porous carbon microspheres The carbon microspheres displayed a narrow size distribution and a high surface area of 679 m2/g coupled with adjustable mesopores and large mesopore volume Carbon microspheres prepared from the dispersion phase with different PF/silica ratios (denoted as carbon/silica (C/Si) ratios) were studied and the formation mechanism of the PF/silica microspheres was deeply explored

1 Introduction

Porous microspheres with size ranging from 100 to 1000 μm are

widely used in various practical applications due to their suitable size for

transportation and recovery [1] Because of the low density, high

chemical stability and thermal conductivity, hundred-micron porous

carbon spheres have been used in air and water purification, blood

pu-rification, CO2 adsorption, and electronic and energy storage devices

[2–11]

So far, polymerization is the most popular method for the

prepara-tion of hundred-micron carbon microspheres [11] and carbon spheres

synthesized from polymers displayed higher mechanical strength [8]

Divinylbenzene-based spherical activated carbon with size between 200

and 1200 μm were used for water purification, i.e removal of organic

pollutants from water [6] The spherical activated carbon showed two

times higher methylene blue adsorption capacity compared to the

commercially available spherical activated carbon However, due to the

low mesopore volume, the highest observed methylene blue adsorption

capacity was only 32 mg/g Yang et al synthesized phenolic resin-based

activated carbon spheres with different pore size distributions by using

polyethylene glycol and polyvinyl butyral as pore-forming agents [7] The size of the mesopores was between 3 and 5 nm in the carbon spheres Therefore, they showed excellent adsorption capacity for large molecules e.g., creatinine and VB12 Activated carbon spheres with the diameter of 200–950 μm were prepared by carbonization of commer-cially available polystyrene-based ion-exchange resin spheres [8] The polystyrene-based activated carbon spheres were 3 times harder than the pitch-based activated carbons spheres Due to the large pore volume

of 1.35 cm3/g, the spheres displayed high adsorption capacity of 153 mg/g for dibenzothiophene Polystyrene-based microporous activated carbon spheres with a narrower size distribution between 500 and 800

μm have been prepared by suspension polymerization of styrene monomer and followed by some post-treatment processes including sulfonation, oxidation, carbonization, and activation The obtained carbon spheres displayed a high surface area (1526 m2/g) and a large pore volume (0.73 cm3/g) The adsorption capacity for CO2 was also high about 4.21 mmol/g at 25 ◦C and ambient pressure [9] A so-called inverse-microemulsion-polymerization-phase-separation method has been developed for the preparation of carbon spheres using phenolic resin [10] The carbon spheres with the size of about 100 μm were

* Corresponding author

** Corresponding author

E-mail addresses: liang.yu@ltu.se (L Yu), lixiongzhang@yahoo.com (L Zhang)

Contents lists available at ScienceDirect Microporous and Mesoporous Materials journal homepage: www.elsevier.com/locate/micromeso

https://doi.org/10.1016/j.micromeso.2022.112186

Received 4 April 2022; Received in revised form 29 July 2022; Accepted 12 August 2022

composed of carbon nanoparticles with the size smaller than 100 nm

Therefore, the carbon spheres displayed a hierarchical structure and

high total pore volume of 2.78 cm3/g Due to the unique structure, the

carbon spheres showed a rapid transport of electrolyte ions, and

there-fore displayed high potential in superior rate performance carbon-based

supercapacitors Polymerization method is easy to scale up However,

the wide size distribution of the spheres products is always a drawback

of the method

Phenolic resin is a decent carbon source for the synthesis of high-

quality carbon microspheres due to the high carbon content However,

the polymerization of phenol and formaldehyde is a relatively slow

process due to the high viscosity of the mixture of phenol and

formal-dehyde [12] Normally, a reaction time of 5 h at 95 ◦C is needed for the

polymerization process [12] Singh et al., prepared macrosize phenolic

beads (100–200 μm) by a suspension polymerization method with the

reaction temperature of 96 ◦C and reaction time of 4 h [13] The

phenolic beads can be used as precursors for the preparation of carbon

sphere However, the beads showed a broad size distribution and poor

structural properties, e.g., low porosity In some cases, additives are

added to improve the formation process and reduce the polymerization

time as well as improve the porosity of the obtained microspheres

[14–16] However, the issue of the broad size distribution of

micro-spheres prepared from the conventional polymerization remains

Therefore, a new method is necessary

As it is well known, microchannel technique could reduce the

reac-tion time and temperature for time consuming and high temperature

demanding systems [17] In addition, microchannel technique could

prepare microspheres with more uniform size compared to the

con-ventional polymerization method [18–20] Steinbacher et al.,

summa-rized the application of microchannel technique for the preparation of

even size microdroplets and microspheres [17] Our group also has

developed several microchannel devices for the preparation of

nano-particles, microspheres, and microcapsule materials in the last 15 years

[18,21–23] Silica microspheres with the uniform size of 100 μm and

various structures including solid, hollow, hollow with a hole and

filbert-like solid structures were prepared in a simple T-type

micro-channel device [21] Monodisperse carbon hollow spheres were also

prepared in such device [18] To improve the textural properties of the

obtained carbon spheres, colloidal silica is often used as additive for the

preparation of porous carbon Our previous report showed that the pore

size of carbon spheres increased from 0.6 to 6.2 nm after removal of

silica nanoparticles from poly (furfuryl alcohol)-silica composite

mi-crospheres [22] Therefore, the adsorption capacity for dye increased

significantly Silica nanoparticles also have been employed to tailor

porosity in carbon spheres using a modified St¨ober method [24] The

obtained carbon spheres showed both microporous and mesoporous

structure with surface areas between 326 and 1500 m2/g and total pore

volumes between 0.26 and 1.22 cm3/g Meanwhile, a high adsorption

capacity of 7.8 mmol/g for CO2 were observed at 0 ◦C and 1 bar [24] So

far, large size (hundred-micron meters) mesoporous carbon spheres with

an even size distribution have rarely been reported

In the present work, hundred-micron carbon spheres with

control-lable porous structure were prepared using a simple microchannel

de-vice in combination with a solvent extraction method PF resin/silica

microspheres were first prepared in the simple microchannel device

The microspheres were carbonized to obtained carbon/silica spheres

Subsequently, porous carbon spheres were prepared after removal of

silica The synthesized time was much shorter and the obtained carbon

spheres were more even compared to the conventional polymerization

method The conditions for the formation of PF resin/silica

micro-spheres in the microchannel device were optimized and the effect of

carbon/silica ratio on the textural properties of the porous carbon

spheres was investigated In addition, the mechanism of the formation of

the microspheres in the microchannel was discussed

2 Experimental

2.1 Preparation of colloidal silica

Colloidal silica with the concentration of about 10 wt% was prepared

by mixing 2.6 g TEOS with 3.0 g ethanol and followed by slowly adding 1.35 g HCl (4 × 10− 3 M) The mixture was stirred for 2 h at room temperature

2.2 Preparation of phenol formaldehyde resol

Phenol formaldehyde resol with a solids content of about 80 wt% was prepared using phenol and formaldehyde (37 wt%) as precursors and 20 wt% NaOH aqueous solution as catalyst as described in previous work [25] A mixture was first prepared by melting 12.2 g phenol at

42 ◦C and subsequently adding 2.6 g 20 wt% NaOH under stirring Af-terwards, formaldehyde solution (21 g) was added to the mixture The mixture was heated to 75 ◦C and maintained for 60 min until the mixture became red The mixture was then cooled down to room temperature and neutralized to pH of 7 using 7 × 10− 2 M HCl The water in the mixture was removed by drying at 45 ◦C for about 2 days The obtained product was dissolved into ethanol to remove the NaCl precipitation Finally, the phenol formaldehyde resol resin was obtained after drying

at 45 ◦C to remove ethanol

2.3 Preparation of carbon microspheres

Fig 1 shows the microchannel device that used in the present work for the preparation of carbon microspheres precursors, i.e phenol formaldehyde resin microspheres The device has been described in our previous work [26]

Briefly, two PTFE tubes (red pipes in Fig 1a) with the inner diameter

of 0.56 mm were fixed in a T-type microchannel for continuous phase The length of the PTFE tube for the outlet of the T-type microchannel was 100 mm A needle with the inner diameter of 0.26 mm was inserted into the other inlet of the T-type microchannel The head of the needle should be placed at 2 mm after the joint point of T as shown in Fig 1a The needle inlet will be used for dispersed phase

The dispersed phase was a mixture of the colloidal silica, phenol formaldehyde resol, and ethanol The ethanol was used to control the solid concentration in the dispersed phase Continuous phase, i.e., the oil phase was a mixture of n-hexane, liquid paraffin, and diisopropylamine The dispersed phase and continuous phase were fed into the T-type microchannel at flowrates of 0.2 and 6.0 ml/h, respectively Liquid microdroplets were formed at the outlet of the needle due to the shearing force of the continuous phase A condenser column with the length of 750 mm and inner diameter of 20 mm connected to a flask was placed under the outlet of the T-type microchannel to collect the generated microspheres (Fig 1b) The composition of the liquid mixture

in the column was the same as the continuous phase The microspheres were maintained in the oil phase for extraction PF resin/silica

Fig 1 Experimental device diagram

microspheres were obtained in the flask after ethanol and water were

extracted The microspheres were cured at 100 ◦C for 12 h and washed

by n-hexane for three times to obtain the solid PF resin/silica

micro-spheres For comparison, solid phenol formaldehyde resin was prepared

by mixing 1.0 g 80 wt% phenol formaldehyde resol with 0.1 g

diiso-propylamine, and subsequently curing at 100 ◦C oven for 12 h The

obtained solid phenol formaldehyde resin was washed by n-hexane for

three times

A tubular furnace was used to carbonize the PF resin/silica

micro-spheres under nitrogen atmosphere The temperature was first increased

to 350 ◦C and maintained for 3 h, followed by increasing to 700 ◦C and

maintained for 7 h Porous carbon microspheres were eventually

ob-tained by immersing the carbon/silica spheres in 10 wt% HF for 2 h to

remove silica nanoparticles Solid phenol formaldehyde resin was

carbonized at the same conditions to prepare carbon for comparison

2.4 Characterizations

An optical microscope (Olympus CX31) and SEM instruments

(Phi-lips Quanta 200 and Hitachi− S4800) were used to observe the

morphology of the obtained products N2 adsorption –desorption

iso-therms were determined at liquid nitrogen temperature using

BEL-SORPII instrument Prior the measurement, the samples were degassed

at 120 ◦C for 6 h to remove any impurity The total pore volume was

calculated at p/p0 of 0.99 and the BET method was used to estimate the

surface area Pore size distributions were analyzed using the non-local

density functional theory (NLDFT) A miniature double-frequency

nu-merical control ultrasonic cleaning machine (KQ-100VDV) was used to

evaluate the mechanical strength of the carbon microspheres The

mi-crospheres were dispersed in water and treated in the ultrasonic

clean-ing machine under a frequency of 45 kHz for 30 min The particles size

distribution of the synthesized colloidal silica was measured using a

Malvern Zetasizer (Nano-ZS) instrument

3 Results and discussion

3.1 Effect of silica contents

Fig 2 shows the photographs of the microspheres prepared using

dispersed phases with different ratios of colloidal silica, phenol

form-aldehyde resol resin, and ethanol The mass ratios of carbon to silicon (m

(C/Si)) in the dispersed phases were ∞, 17 and 15 However, the total

content of solid in the dispersed phase was maintained constant at 35 wt

% The continuous phase was comprised of n-hexane, liquid paraffin,

and diisopropylamine with the volume ratio of 2:2:1

Fig 2 shows that a large liquid droplet was generated from the small

droplets prepared without colloidal silica, i.e., the droplets

agglomer-ated when the m (C/Si) was infinity This was due to the condensation

polymerization of phenol formaldehyde resol is a slow process and an

alkaline catalyst is needed, otherwise, the short residence time in the

condensation column was not sufficient for the formation of stable

phenol formaldehyde resin microspheres Therefore, a large liquid

droplet was obtained in the flask However, stable PF/silica

micro-spheres could be formed in the column due to the gelation of colloidal

silica Spherical product could be obtained when m (C/Si) was 17, but the microspheres agglomerated slightly, see Fig 2b This resulted from the low colloidal silica concentrations Monodispersing microspheres were obtained when m (C/Si) decreased to 15, i.e., when the concen-tration of colloidal silica increased The well dispersing microspheres formed in the column provided promising microspheres precursors for the late high temperature curing and carbonization

Fig 3 shows the SEM images of the PF/silica microspheres prepared from a mixture with m (C/Si) of 15 The microspheres have a uniform size of about 150 μm, which is much smaller than the liquid micro-spheres generated from the microchannel due to the contraction during extraction To investigate the formation process of the PF/silica micro-spheres, more experiments were carried out using dispersed phase with different m (C/Si) Different amounts of ethanol were used to maintain a constant solid concentration in the dispersed phase The size of the microdroplets at the outlet of the needle was 400 μm Fig 4 shows the variations of the microdroplets in the extract as a function of extracting time, which prepared from the m (C/Si) of 15, 13, 11, 8.5, and 6.5, respectively

Fig 4 shows that the freshly generated microdroplets are trans-parent, no matter with the ratio of m (C/Si), and the microdroplets became dark with the increase of the extracting time due to the gelation

of colloidal silica and the polymerization of phenol formaldehyde resol The color of the microdroplets changed evenly when m (C/Si) ≥11 However, with the decrease of m (C/Si), i.e., increased the colloidal silica content, a transparent shell and a dark core were observed, which

Fig 2 Photographs of the obtained PF/silica microspheres with different m

(C/Si), (a) ∞; (b) 17; (c) 15 Fig 3 SEM images of (a) the overall morphology and (b) the surface of PF/ silica microspheres with m (C/Si) = 15

Fig 4 Optical micrograph of the process of extraction of microdroplets

pre-pared from m (C/Si) of 15 (a), 13 (b), 11 (c), 8.5 (d), and 6.5 (e) The size of the scale is 400 μm

probably resulted from the phase separation during the gelation of

colloidal silica (water phase) and the polymerization of phenol

formal-dehyde resol (oil phase)

Meanwhile, the particle size of the obtained PF/silica microspheres decreased with the increase of the m (C/Si) as shown in Fig 5, which showed that the content of colloidal silica has a significant effect on the microsphere size It is important to note that the total solids content in the dispersed phase was maintained constant at 35 wt% as mentioned above when m (C/Si) was changed More information about shell and core is explored as below

Fig 6 shows the PF/silica microspheres prepared from different ra-tios of m (C/Si) Silica gel, i.e., a hydrogel with three-dimension struc-ture will generate in the microdroplets when the content of colloidal silica was high Therefore, a more porous structure was obtained in the microspheres, see Fig 6b Microspheres with more compact structure was observed when the content of colloidal silica decreased, i.e., the content of phenol formaldehyde resol increased Since diisopropylamine

in the extract catalysed the polymerization of phenol formaldehyde resol, the compact structures, mainly the compact shells were generated

in the microsphere Therefore, the PF/silica microspheres with shells thickness of about 4 μm, 15 μm and 18 μm were observed, when m (C/Si) increased from 6.5 to 15, see Fig 6 We, therefore, can conclude that the core and the shell of PF/silica microspheres were mainly silica and phenol formaldehyde resin, respectively

3.2 Effect of diisopropylamine concentration

Diisopropylamine was selected as catalyst for the polymerization of

Fig 5 Size of PF/silica microspheres as a function of m (C/Si)

Fig 6 SEM images of the whole, surface, cross-section and edge of the cross-section of the PF/silica microspheres prepared at m (C/Si) = 6.5 (˜ad), m (C/Si) = 13 (e

~ h), and m (C/Si) = 15 (i ~ l)

Fig 7 SEM images of cross-section of PF/silica microsphere prepared at m (C/Si) = 15 and different diisopropylamine concentrations, (a) 10 wt%; (b) 40 wt%; (c)

60 wt%, and the cross-section edge of (d) 10 wt%, (e) 40 wt%, (f) 60 wt%

phenol formaldehyde resol Meanwhile, it could enhance the gelation of

colloidal silica The advantages of diisopropylamine catalyst are the

lower reaction temperature, and high solubility in n-hexane and liquid

paraffin

Since the pH of the colloidal silica used in the present work was

about 5, silica gel was formed when the microspheres interacted with

diisopropylamine The concentration of diisopropylamine will affect the

gelation rate of colloidal silica and the polymerization rate of phenol

formaldehyde At low diisopropylamine concentration, the gelation and

polymerization rate were low Diisopropylamine could diffuse into the

microspheres before polymerization completed, therefore the elements

distribution was quite even However, when the diisopropylamine

concentration was high, phenol formaldehyde will be polymerized at the

surface of the microspheres quickly, and more phenol formaldehyde

resol will diffuse to the surface for polymerization Meanwhile, some

diisopropylamine will diffuse into the microsphere and therefore silica

gel formed inside the microspheres This process is similar to phase

separation In addition, silicate could be generated when the pH is high enough, i.e., at high diisopropylamine concentration, which could be easily rinsed away Therefore, the carbon content will be high and silica content will be much lower at the surface These explain the formation

of shell on the surface of the microspheres (see Fig 7c, f) and the lower

silicon in the shell when the concentration of diisopropylamine increased to 60 wt% Table 1 summarizes the elements distribution in the microspheres

The effect of diisopropylamine concentration on the formation pro-cess of the microspheres were further explored by observing the change

of the microdroplets in the extract with different compositions Fig 8 shows the change of the colour of the microdroplets in the extract with low diisopropylamine concentration The microspheres became dark evenly However, the results in Fig 9, where the diisopropylamine concentration was higher, show a shell on the microsphere due to the fast polymerization of phenol formaldehyde on the surface and gelation

of colloidal silica in the centre These images show clear phase separation

3.3 Textural properties of the microspheres

Fig 10 shows the SEM images of the microspheres after curing, carbonization and removal of silica Moreover, the microspheres were prepared from a dispersed phase with m (C/Si) = 11 and solid content of

35 wt%

As it has been mentioned above, the microdroplets generated at the outlet of the needle were about 400 μm However, the size of the mi-crospheres was contracted to about 260 μm after polymerization and extraction The size of the microsphere further decreased to about 170

μm after carbonization, and the sizes before and after removal of silica were almost the same

Fig 11 shows the N2 adsorption-desorption isotherms of micro-spheres prepared at different conditions The adsorption solely occurred

at the initial pressure range for carbon/silica and carbon microspheres, which indicates only micropores generated in the microspheres The micropores similar with the activated carbon More micropores and mesopores were generated after removal of silica Fig 11 shows the pore size distributions of the obtained microsphere at different conditions The mesopores sizes of the carbon microspheres synthesized from C/Si

=6.5 was in the range of 5.7–8.3 nm Larger mesopores up to 12.3 nm were observed in the carbon microspheres prepared from C/Si = 11 Only micropores could be observed in C(PF) particles The micropo-rosity in the carbon microspheres also increased after silica removal, and the size of the micropores is much smaller than the size of the silica particles in the colloidal silica (Fig 11d) This indicated that even smaller silica particles were generated in the carbon/silica micro-spheres The smaller silica particles were probably developed from the dissolution of the TEOS-generated silica during the experiment [27,28] Table 2 summarizes the textural properties of the prepared micro-spheres at different conditions The surface area of pure carbon was only

126 m2/g, which was much smaller than the carbon/silica microspheres The surface area of carbon/silica microspheres increased significantly after removal of silica For instance, the surface area of carbon/silica microspheres prepared from a dispersed phase with m (C/Si) = 6.5 was

329 m2/g, and it increased to 679 m2/g after removal of silica, mean-while, the total pore volume increased from 0.15 to 0.50 cm3/g These results indicated that colloidal silica was used not only as the assistant for the formation of the spherical structure, but also for the generation of porous structure, especially for the mesoporous structure, which makes the microsphere a wide application at macromolecules adsorption, drug delivery, supercapacitors, and catalysis It is important to note that the microspheres well preserved the spherical morphology (Fig 10) after the treatment in an ultrasonic bath (45 kHz) for 30 min The results indicated a good mechanical strength of the carbon microspheres Porous carbon materials have been extensively studied in the last decades Macropore-rich activated carbon microspheres with size of

Table 1

Effect of diisopropylamine concentration on the distribution of elements in PF/

silica microspheres

Diisopropylamine

concentration (wt.%) Distribution of elements in core/shell of the microsphere (wt.%)

59.43 6.65/ 2.82 0.06/ 2.41 30.20/ 35.34

57.24 8.68/ 4.61 1.49/ 3.88 24.55/ 34.26

61.55 14.05/ 3.19 0.09/ 4.03 34.24/ 31.23

Fig 8 Optical micrographs of the extraction process of PF/silica microdroplets

in the extraction phase The PF/silica were prepared with C/Si = 15 and solid

content of 35 wt% The composition of extraction phase was liquid paraffin: n-

hexane: diisopropylamine = 8:9:3 The size of the scale is 400 μm

Fig 9 Optical micrographs of the extraction process of PF/silica microdroplets

in the extraction phase The PF/silica were prepared with C/Si = 15 and solid

content of 35 wt% The composition of extraction phase was liquid paraffin: n-

hexane: diisopropylamine = 8:3:9 The size of the scale is 300 μm

about 100 μm have been prepared using inverse-microemulsion-

polymerization-phase-separation coupling method The polymerization

was performed at 120 ◦C for 12 h Phenolic resin was used as carbon

source, ethylene glycol was used as pore generator and

hexamethy-lenetetramine was used as the hardener for polymerization The carbon

microspheres displayed a surface area as high as 1622 m2/g, but almost

no mesoporous was observed [10] In addition, the microemulsion

polymerization method is batch with complicated operation procedures,

i.e., mixing and temperature control, and the prepared microsphere

normally showed a wide particle size distribution The method using

microchannel technology can produce microspheres continuously with

narrow size distributions, and the temperature in microchannel is even

due to the enhanced heat transfer In addition, the microspheres are

formed in a much shorter time about 15 min in the microchannel at

room temperature Colloidal silica is more economical than the other

organic pore generators, and the microchannel method is easy to scale

up, which shows high potential for large applications

4 Conclusions

Carbon/silica microspheres and carbon microspheres with a size of hundred-micron have been successfully prepared using microchannel technique The process was quite economical due to the gentle reaction conditions, i.e., room temperature and short reaction time Colloidal silica can significantly reduce the time for the formation of microsphere due to the gelation The use of colloidal silica can also increase surface area and pore volume, both microporous and mesoporous, significantly The textural properties of the microspheres can be adjusted easily by colloidal silica content, which enables the microsphere material a great potential as macromolecules adsorbent, drug delivery material,

Fig 10 SEM images of microspheres after (a) aging; (b) carbonization; (c) removal of SiO2 by hydrofluoric acid The dispersed phase that used for the preparation of the microspheres had a m (C/Si) = 11 and solid content of 35 wt% SEM images with different magnifications (d) and (e) of the microspheres after treatment in an ultrasonic bath (45 kHz) for 30 min

Fig 11 (a) N2 adsorption-desorption isotherms; (b) and (c) NLDFT pore size distributions of carbon/silica microspheres and carbon microspheres after removal of SiO2; (d) particle size distribution of the colloidal silica prepared in the present work

stationary phase of chromatography, supercapacitor, and catalyst

carrier

Notes

The authors declare no confliction of interest

CRediT authorship contribution statement

Jie Li: Writing – original draft, Investigation, Formal analysis

Zhenheng Xu: Investigation, Formal analysis Liang Yu: Writing –

re-view & editing, Supervision, Formal analysis, Data curation Lixiong

Zhang: Writing – review & editing, Funding acquisition,

Conceptualization

Declaration of competing interest

The authors declare that they have no known competing financial

interests or personal relationships that could have appeared to influence

the work reported in this paper

Data availability

Data will be made available on request

Acknowledgment

The authors acknowledge the financial support from the Priority

Academic Program Development of Jiangsu Higher Education

Institutions

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Table 2

Summary of the textural properties of different mesoporous carbon

microspheres

Microspheres Particle

size (μm) Surface area (m 2 /

g)

Total pore volume (cm 3 /g)

d p

(nm) Ref

C(PF) particles n/a 126 0.07 1.57 This

work Carbon/silica

microspheres a 170 295 0.14 1.3 This

work Carbon

microspheres a 170 625 0.38 11.3 This

work Carbon/silica

microspheres b 174 329 0.15 1.4 This

work Carbon

microspheres b 174 679 0.50 6.2 This

work Activated carbon

microspheres ~100 1622 2.78

>10 [ 10 ] Macroporous

carbon spheres 0.4 451 0.28 n/a [29]

Ordered

mesoporous

carbon sphere

Phenolic resin-

based carbon

spheres

a and b microspheres prepared from dispersed phases with m(C/Si) = 11 and 6.5,

respectively