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Nano Res
1
Controlled synthesis of sustainable n-doped hollow
core mesoporous shell carbonaceous nanospheres
from biomass
Chuanlong Han, Shiping Wang, Jing Wang, Mingming Li, Jiang Deng, Haoran Li and Yong Wang()
Nano Res., Just Accepted Manuscript • DOI: 10.1007/s12274-014-0540-x
http://www.thenanoresearch.com on July 9, 2014
© Tsinghua University Press 2014
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Nano Research
DOI 10.1007/s12274-014-0540-x
TABLE OF CONTENTS (TOC)
Controlled Synthesis of Sustainable N-doped Hollow
Core Mesoporous Shell Carbonaceous nanospheres
from Biomass
Chuanlong Han, Shiping Wang, Jing Wang, Mingming
Li, Jiang Deng, Haoran Li and Yong Wang*
Carbon Nano Materials Group, Center for Chemistry of
High-performance and Novel Materials, Department of
Chemistry, Zhejiang University, Hangzhou 310028, P. R.
China.
N-doped hollow core disordered mesoporous shell carbonaceous
nanospheres (HCDMSs) are synthesized from a sustainable biomass
(glucosamine hydrochloride). The obtained materials possess suitable
nitrogen contents (~6.7-4.4 wt %), high specific surface areas (770 m2
g-1), controlled size (~450-50 nm), and tunable shell thickness (~70-10
nm). To our excitement, these HCDMSs exhibited striking
electrocatalytic activity, which was free from the crossover effect, and
its long-term durability was superior to that of commercial Pt/C (20
wt%).
http://mypage.zju.edu.cn/chemwy
Controlled synthesis of sustainable n-doped hollow
core mesoporous shell carbonaceous nanospheres
from biomass
Chuanlong Han, Shiping Wang, Jing Wang, Mingming Li, Jiang Deng, Haoran Li and Yong Wang()
Received: day month year
Revised: day month year
Accepted: day month year
(automatically inserted by the
publisher)
© Tsinghua University Press
and Springer-Verlag Berlin
Heidelberg 2014
KEYWORDS
n-doped,
biomass,
hollow nanospheres,
oxygen reduction reaction
ABSTRACT
Encompassing ecological and economic concerns, the utilization of biomass to
produce carbonaceous materials has attracted intensive research and industrial
interest. Using nitrogen containing precursors could realize an in situ and
homogeneous incorporation of nitrogen into the carbonaceous materials with a
controlled process. Herein, N-doped hollow core disordered mesoporous shell
carbonaceous nanospheres (HCDMSs) were synthesized from glucosamine
hydrochloride (GAH), an applicable carbohydrate-based derivative. The
obtained HCDMSs possessed controlled size (~450-50 nm) and shell thickness
(~70-10 nm), suitable nitrogen contents (~6.7-4.4 wt %), and BET surface areas
up to 770 m2 g-1. These materials show excellent electrocatalytic activity as
metal-free catalyst for the oxygen reduction reaction (ORR) in both alkaline and
acidic media. Specifically, the prepared HCDMS-1 exhibits a high
diffusion-limited current, superior durability, and wonderful immunity
towards methanol crossover and CO poisoning for ORR in alkaline solution,
compared with those of commercial 20 wt % Pt/C catalyst.
1 Introduction 1
2
The synthesis of hollow carbonaceous spheres 3
(HCSs) has attracted a lot of attention due to their 4
unique properties, such as high surface-to-volume 5
ratios, low density and excellent thermal and 6
chemical stability [1-6]. Therefore, HCSs are 7
promising materials with diverse applications such 8
as fuel cells [7-10], lithium-ion batteries [11-14], 9
capacitor [15], adsorbent [16], catalyst supports 10
[17-20] and so on. Many efforts have been devoted 11
to the synthesis of HCSs by a nanocasting approach 12
which is considered to be the most straightforward 13
Nano Research
DOI (automatically inserted by the publisher)
Research Article
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2 Nano Res.
way to create hollow structure [21, 22]. In addition, 1
the hollow core mesoporous shell carbonaceous 2
spheres (HCMSs) or capsules with tailorable 3
diameter, shell thickness and surface properties are 4
novel and promising nanomaterials [23, 24]. The 5
HCMSs have bimodal pore systems of tunable 6
hollow macroscopic core and mesoporous shell. As 7
the hollow cavity can act as a nanoreactor and the 8
shell provides controlled release pathways for the 9
encapsulated substances and vast surface area for 10
reactions, they have a wide range of applications 11
[25]. 12
Carbon precursors have a pivotal effect on the 13
preparation and final physical and chemical 14
properties of the obtained carbonaceous materials 15
[19, 26, 27]. In most cases, the surface of the 16
template is incompatible with the carbon source. 17
Fortunately, this can be solved by selectively 18
functionalizing the surface of the template with 19
prospective functional groups or electrostatic 20
charges. Usually, the precursors are phenol 21
formaldehyde resin [28-31], polyaniline [32], 22
polyacrylonitrile [33, 34], styrene [35], acetonitrile 23
[36], benzene [37, 38] and ethylene [39], all of which 24
are easy to be coated on the surfaces of the 25
templates. In recent years, the utilization of biomass 26
to synthesize carbonaceous materials has attracted 27
much research and industrial interest because of the 28
ecological and economic concerns [40-44]. Glucose 29
[3, 45, 46], sucrose [47], fructose [48], starch [49], 30
furfural [50, 51], dopamine [19], and grass [52, 53] 31
have been used as renewable and inexpensive 32
carbon sources with suitable carbon yield. This is a 33
dramatic and exciting development in the 34
production of carbonaceous materials. However, 35
the majority of the resulted carbonaceous materials 36
are bulk carbon without functional atoms or groups 37
in the matrix or on the surface [54]. 38
It is well known that the nitrogen dopant can 39
improve the properties of bulk carbon, such as the 40
conductivity, oxidation stability, basicity and 41
catalytic activity [55-59]. Nitrogen-doping into 42
carbonaceous materials can be realized either in situ 43
doping during the synthesis or by post-treatment 44
after the synthesis. In fact, using nitrogen 45
containing precursors can achieve a homogeneous 46
incorporation of nitrogen into the bulk 47
carbonaceous materials via the in situ doping 48
method. Herein, we developed a straightforward 49
and versatile method to prepare N-doped hollow 50
core disordered mesoporous shell carbonaceous 51
nanospheres (HCDMSs) using cheap and easy 52
available carbohydrate-based derivative, i.e. 53
glucosamine hydrochloride (GAH) as both carbon 54
and nitrogen precursor. The approach produced 55
N-doped HCDMSs with high surface areas (770 m2 56
g-1), controlled size and shell thickness, and nice 57
degree of graphitization. Furthermore, these 58
functional materials exhibited practical applications 59
in catalysis and electrochemistry. Here, they served 60
as metal-free catalysts for the oxygen reduction 61
reaction (ORR) with excellent electrocatalytic 62
activity in both alkaline and acidic solution. 63
64
2 Experimental 65
66
2.1 Materials 67
68
Ammonium hydroxide (NH4OH, 25-28 wt%), 69
potassium hydroxide (KOH, AR), perchloric acid 70
(HClO4, AR), ethanol (AR) were used as received 71
from Sinopharm Chemical Reagent Co., Ltd. 72
Tetraethyl orthosilicate (TEOS, AR), 73
trimethoxy(octadecyl)silane(90%, C18-TMS), 74
D(+)-Glucosamine hydrochloride (GAH, ≥99%), 75
NH4HF2 (AR, >98.5%) were used as received from 76
Aladdin Chemistry Co., Ltd. Nafion 117 solution (5 77
wt%) was obtained from Aldrich Chemistry Co., 78
Ltd. 20 wt% Pt/C was used as received from Alfa 79
Aesar Chemistry Co., Ltd. All the chemicals were 80
used as delivered without further treatment. 81
82
2.2 Synthesis of solid core disordered 83
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3 Nano Res.
mesoporous shell silica spheres (SCDMSs) 1
2
Typically, taking the synthesis of SCDMS-1 as an 3
example: Firstly, 3.14 ml of ammonia hydroxide was 4
added into a solution containing 74 ml of ethanol 5
and 10 ml of deionized water, and then the mixed 6
solution was stirred at 30 oC for 0.5 h. Secondly, 6 ml 7
of TEOS was added into the above-prepared 8
mixture quickly under vigorous stirring and the 9
reaction mixture was kept stirring for 1 h to yield 10
uniform silica spheres (Stöber silica sol [60]). Then, 11
a mixture of 2 ml C18-TMS and 5 ml TEOS was 12
added dropwise to the above solution with 13
magnetic stirring to create a thin mesoporous silica 14
shell around the dense silica core [61]. The mixed 15
solution was then kept at 30 oC for 1h without 16
stirring to promote the cohydrolysis and 17
condensation of the C18-TMS and TEOS on the silica 18
core. Finally, the nanostructured silica was 19
centrifuged, dried at 70 oC overnight and calcined at 20
550 oC for 6 h in air. 21
22
2.3 Synthesis of hollow core disordered 23
mesoporous shell carbonaceous nanospheres 24
(HCDMSs) 25
26
Taking the synthesis of HCDMS-1 as an example: 27
Firstly, a solution of SCDMS-1 (1.0 g) and GAH (1.0 28
g) was mixed together adequately and then dried at 29
60 oC under magnetic stirring. The mixture was then 30
transferred into a 25 ml-crucible which was placed 31
in 100 ml-Teflon-lined autoclave with 10 ml 32
deionized water inside. Hydrothermal 33
carbonization was performed in a standard 34
laboratory oven, heated at 180 oC for 24 h. Then, the 35
composite material was calcined to the desired 36
temperature over a ramp stage of 90 minutes (10 oC 37
min-1 for HCDMS-1) followed by an isothermal hold 38
period of 1 h in a Muffle furnace in N2 flow (400 39
mL/min). After it cooled down to room 40
temperature, loose black solid was gained. Then the 41
black solid was ground into black powder and 42
transferred into a plastic bottle, 40 g NH4HF2 and 43
160 g deionized water were also added into the 44
bottle. The mixtures were stirred for 48 hours at 45
room temperature. After filtering the solution, the 46
black solid residue was dried at 70 oC in an oven 47
overnight. The obtained SCDMSs and HCDMSs 48
were denoted as SCDMS-X and HCDMS-X 49
respectively, where X was a sample number that 50
represent the different diameters (Table S1 in the 51
Electronic Supplementary Material (ESM)). And 52
HCDMS-2 (3, 4, 5) was prepared with the same 53
process except different template SCDMS-2 (3, 4, 5). 54
55
2.4 Characterization: 56
57
SEM images were obtained on a Sirion-100 58
microscope. TEM studies were performed on a 59
Hitachi HT-7700 microscope. High-Solution TEM 60
(HRTEM), STEM-HAADF and STEM-EDX were 61
performed on Tecnai G2 F30 S-Twin at an 62
acceleration voltage of 300 kV. Powder X-ray 63
diffraction (XRD) patterns were measured on a 64
D/tex-Ultima TV wide angle X-ray diffractometer 65
equipped with Cu Kα radiation (1.54 Å). The X-ray 66
photoelectron spectra (XPS) were obtained by an 67
ESCALAB 250Xi spherical analyzer using an 68
aluminum node (Al 1486.6 eV) X-ray source. The 69
Raman spectra were collected on a Raman 70
spectrometer (JY, HR 800) using 514-nm laser. The 71
BET surfaces were determined by ASAP 2020 HD88, 72
BET equation was used to calculate the surface 73
areas and pore volume and samples were degassed 74
at 200 oC for 8 h until the residual pressure was less 75
than 10-4 Pa. The element analysis was carried out 76
on the Flash EA 1112, ThermoFinnigan. 77
78
2.5 Electrochemical characterization 79
80
Electrochemical measurements were performed 81
using a computer-controlled workstation (LK2005A, 82
China) with a typical three-electrode cell. Rotating 83
disk electrode (RDE) was used as working electrode, 84
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4 Nano Res.
a platinum sheet as counter electrode and saturated 1
calomel electrode (SCE) as reference electrode. The 2
activity of the materials was evaluated by the CV 3
and LSV techniques. Fabrication of the working 4
electrode was done by pasting catalyst inks on a 5
glassy carbon electrode (5 mm in diameter, from 6
Pine). The carbon ink was formed by mixing 10 mg 7
of HCDMS catalyst, 50 µL 5 wt% Nafion solution 8
and 500 µL ethanol in a plastic vial under 9
ultra-sonication for 20 min. A 5 µL aliquot of the 10
carbon ink was dropped on the surface of the glassy 11
carbon electrode, yielding the final catalyst loading 12
of approximate 0.46 mg/cm2. For comparison, the 13
commercial 20 wt% Pt/C catalyst ink was dealt with 14
in the same method. All the experiments were 15
conducted at room temperature. 16
17
3 Results and discussion 18
19
The overall synthetic procedure was shown in Fig. 1. 20
In the synthesis, SCDMSs were applied as sacrificial 21
templates and GAH was used as the carbon source 22
and nitrogen source. The SiO2 solid core was 23
synthesized according to the Stöber method using 24
TEOS as the precursor. To obtain the mesoporous 25
silica shell, another batch of TEOS was added with 26
C18-TMS as a porogen and calcined at 550 oC. 27
Through the screening of various synthetic 28
conditions such as the amount of NH4OH, TEOS 29
and C18-TMS, the diameter and the thickness of 30
mesoporous silica shell can be controlled (Table S1 31
in the Electronic Supplementary Material (ESM)). 32
These monodisperse SCDMSs were then used as 33
templates to synthesize HCDMSs. Briefly, GAH 34
was adsorbed on the surface of the SCDMSs and 35
partly incorporated into the mesoporous silica shell 36
to gain GAH/silica hybrids during the water 37
evaporation process. Then the GAH/silica hybrids 38
were subsequently converted to polymer/silica 39
composites via the self-condensation and 40
polymerization of GAH at 180 oC during the HTC 41
procedure. The polymer/silica nanocomposites 42
obtained were then carbonized at elevated 43
temperature (900 oC) to convert the coated polymer 44
into carbonaceous materials, followed by washing 45
the carbon/silica composite in NH4HF2 to remove 46
the silica template to gain HCDMSs. The detailed 47
synthetic process was presented in the experimental 48
section. 49
50
Figure 1 Schematic illustration for the synthesis of HCDMSs. 51
52
The diameter and shell thickness of HCDMSs 53
were tailorable concurrently by tuning the synthesis 54
conditions, using hard template method. This 55
56
Figure 2 Characterization results of the HCDMSs with tunable 57
diameters and shell thicknesses. (A, C and E) SEM images of 58
HCDMS-1, HCDMS-2 and HCDMS-3; (B, D and F) TEM 59
images of HCDMS-1, HCDMS-2 and HCDMS-3, separately. 60
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5 Nano Res.
method has been widely adopted since it is 1
straightforward to apply and has obvious 2
advantages for controlling the size, shape and 3
structure of the products. Here, uniform HCDMSs 4
with varying diameters of HCDMS-1 (450±40 nm), 5
HCDMS-2 (220±20 nm), and HCDMS-3 (45±12 nm) 6
were synthesized (Fig. 2 and Fig. S4). The diameters 7
of the HCDMSs were strongly related to the 8
diameters of the SCDMSs which could be controlled 9
by tailoring the concentration of NH4OH and the 10
amount of TEOS and C18-TMS together (Fig. S1 and 11
Table S1 in the ESM). And the shell thicknesses 12
were (70±7), (35±5), and (9±3) nm for HCDMS-1, 13
HCDMS-2, and HCDMS-3, separately. The shell 14
thickness of the HCDMSs was turned by adjusting 15
the amount of TEOS and C18-TMS. As presented in 16
Fig. 3, SCDMS-1, SCDMS-4, and SCDMS-5 were 17
synthesized with the same silica core size but 18
different mesoporous SiO2 shell thickness (80±10), 19
(60±7), and (40±5), accordingly. When using them 20
(SCDMS-1, SCDMS-4, and SCDMS-5) as the seeds, 21
three different HCDMSs (HCDMS-1, HCDMS-4, 22
and HCDMS-5) can be prepared with the same core 23
size, but with different shell thicknesses of (70±7), 24
(60±7), and (35±5) nm, respectively. Hence, the 25
synthesis of HCDMSs with controlled diameter and 26
shell thickness has been successfully exhibited. The 27
details of the local structure of HCDMSs were 28
conducted by High-resolution transmission electron 29
microscopy (HRTEM). 30
Fig. 3 (G, G1 and G2) depicted the HRTEM 31
images of the edge and central views of HCMDS-1. 32
HRTEM studies of hollow carbonaceous 33
nanosphere suggested that the carbonaceous 34
materials contained a disordered mesoporous 35
structure. The combination of the nitrogen sorption 36
(Fig. 5) and HRTEM results clearly revealed that the 37
HCDMS-1 possessed uniform and disordered pore 38
channels. To verify the structural and compositional 39
details of HCDMS-1, STEM-HAADF imaging and 40
STEM-XEDX mapping analysis were carried out 41
upon it (Fig. 4). In agreement with expectations, 42
43
Figure 3 Characterization results of the SCDMSs and 44
HCDMSs with tunable shell thickness. TEM images of (A) 45
SCDMS-1, (B) SCDMS-4, (C) SCDMS-5, (D) HCDMS-1, (E) 46
HCDMS-4 and (F) HCDMS-5. HRTEM images of (G, G1, G2) 47
HCDMS-1. 48
49
element mapping illustrated a homogeneous 50
distribution of nitrogen, carbon and oxygen 51
throughout the sample. 52
53
Figure 4 A representative STEM-HAADF image of HCDMS-1 54
particle and the corresponding STEM-XEDX maps of the C-Kα, 55
N-Kα, O-Kα signals. 56
57
Typical nitrogen adsorption/desorption isotherms 58
at 77 K for the SCDMSs and HCDMSs were 59
investigated (Fig. 5). The isotherms for all the 60
samples synthesized in this work exhibited the type 61
IV isotherm characteristic of mesoporous materials 62
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6 Nano Res.
according to the IUPAC nomenclature. The BET 1
surface area, total pore volume and pore size for the 2
samples were listed (Table 1 and Table S2 in the 3
ESM). The synthesis procedure employed here 4
allowed HCDMSs, which retained the morphology 5
and size of the silica precursor, to be obtained. The 6
resulting pore size distribution of HCDMSs 7
calculated from the desorption branches of nitrogen 8
isotherms by the BJH method was consistent with 9
the size of SCDMSs (Fig. 5C and D). As the pore 10
size distribution was only weakly changed in the 11
carbonaceous materials, we could exclude a 12
homogeneous carbon “nanocoating” on the pore 13
walls. This is consistent with the TEM and 14
STEM-XEDX images discussed above, which 15
showed a wonderful incorporation of the 16
carbonaceous materials. 17
18
Figure 5 N2 adsorption/desorption isotherms of (A) SCDMS-1, 19
SCDMS-4 and SCDMS-5; (B) HCDMS-1, HCDMS-4 and 20
HCDMS-5. Corresponding desorption pore size distributions of 21
(C) SCDMS-1, SCDMS-4 and SCDMS-5; (D) HCDMS-1, 22
HCDMS-4 and HCDMS-5; (E) BET surface areas versus shell 23
thickness; (F) BET surface areas versus average pore diameter. 24
25
Furthermore, it is interesting to find that: An 26
increase of the carbonaceous shell thickness from 36 27
to 59 to 70 nm led to an increase of the total surface 28
area (calculated by the BET method) from 402 to 724 29
to 770 m2/g (HCDMS-5, HCDMS-4 and HCDMS-1), 30
accordingly (Fig. 5E). In addition, with a decrease of 31
desorption average pore diameter from 7.9 to 6.0 to 32
4.8 nm, the specific surface area increased from 402 33
to 724 to 770 m2/g (HCDMS-5, HCDMS-4 and 34
HCDMS-1), respectively (Fig. 5F). It could be 35
concluded as follows: on the one hand, the smaller 36
the pore sizes in the porous carbonaceous materials 37
were, the higher surface areas were; On the other 38
hand, the mesoporous distributed in the shell of 39
HCDMSs made the most contribution to the specific 40
surface areas. Although the cavity sizes of 41
HCDMS-1, HCDMS-2 and HCDMS-3 were different, 42
they also had the same trend (Fig. S3 in the ESM). 43
44
Table 1 Specific surface area and elemental composition of the 45
HCDMSs. 46
Sample SBET
(m2 g-1)
Pore Volume
(cm3 g-1)
Pore Size
(nm)a N (%)
HCDMS-1 770 1.18 4.8 6.0
HCDMS-2 382 0.89 7.0 4.4
HCDMS-3 195 0.62 14.6 4.9
HCDMS-4 724 1.33 6.0 6.7
HCDMS-5 402 0.90 7.9 4.9
a. BJH desorption average pore diameter 47
48
To assess the effective introduction of N atom in 49
the carbonaceous materials, elemental analysis (EA) 50
and X-ray photoelectron spectroscopy (XPS) were 51
carried out (Fig. 6 and Table 1 and Table S3 in the 52
ESM). As shown in Table 1, the nitrogen content 53
analyzed by EA could be varied from 4.4 wt% for 54
HCDMS-2 to 6.7 wt% for HCDMS-4. EA gives 55
analytical information on the bulk of the materials, 56
while XPS is an important chemical analytical tool 57
for the surface assessments, giving the chemical 58
composition of material surfaces with depth down 59
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7 Nano Res.
to 1-10 nm. Additional information of N-doping 1
type was then provided by XPS. The high 2
resolution N1s spectrum could be deconvoluted into 3
four different signals with binding energies of 398.6, 4
400.1, 401.3, and 403.5 eV, corresponding to 5
pyridinic (N1), pyrrolic (N2), graphitic quaternary 6
nitrogen (N3), and pyridine-N-oxide groups (N4), 7
respectively (Fig. 6A). For HCDMS-1, graphitic 8
quaternary nitrogen (48.3 %) and pyridinic nitrogen 9
(27.3 %) species were pronounced, indicating that 10
nitrogen was dominantly incorporated into the 11
graphitic structure. The bonding, graphitic order 12
and crystallinity of HCDMS-1 were studied by 13
Raman spectroscopy (Fig. 6B) and powder XRD (Fig. 14
S2 in the ESM). The G band at ~1590 cm-1 indicated 15
the in-plane vibration of sp2 carbon atoms including 16
C-C and N-C, while the D band at ~1350 cm-1 was 17
associated with the sp3 defect sites and a 18
defect-induced Raman feature, representing the 19
nonperfect crystalline structure of the material. The 20
graphitized nature of this sample was also 21
confirmed by XRD analysis. XRD peaks observed at 22
2 Theta of ~ 25O and 45O could be identified as (002) 23
and (101) reflections of a well-developed graphitic 24
carbon. From elemental analysis, powder XRD and 25
HRTEM, it could be deduced that the materials 26
produced by thermal condensation of GAH 27
featured a graphitic structure even when 28
carbonized at moderate temperatures, while a 29
reasonably proper amount of nitrogen was 30
incorporated in the structures. 31
32
Figure 6 (A) and (B) XPS curve and Raman spectrum of 33
HCDMS-1, respectively. 34
35
As discussed above, the HCDMSs fabricated from 36
the GAH precursor with a metal-free process, 37
which enabled a correlation between their structure 38
characteristics and electrochemical activity. The 39
electrocatalytic properties of the HCDMSs for ORR 40
were then evaluated by cyclic voltammetry (CV) 41
and linear sweep voltammetry (LSV) using a 42
standard three-electrode configuration. CV curves 43
of HCDMSs were carried out in 0.1 M KOH 44
solution saturated with oxygen at a scan rate of 50 45
mV s-1 (Fig. 7 A, B). The reduction current appeared 46
as a well-defined cathodic peak, which suggested 47
obvious electrocatalytic activity for oxygen 48
reduction. To gain further insight into the ORR 49
activity of HCDMSs, the reaction kinetics was 50
studied by rotating-disk voltammetry. As shown in 51
Fig. 7C, the onset potential of HCDMS-4 was more 52
positive than HCDMS-1 and HCDMS-5. The shell 53
thickness and average pore diameter of HCDMS-4 54
are both middle among them, which suggested that 55
moderate shell thickness and average pore diameter 56
were favorable factors for ORR performance of 57
HCDMSs with close nitrogen contents. In addition, 58
the onset potential and plateau current increased 59
from HCDMS-3 to HCDMS-2 to HCDMS-1 (Fig. 7D), 60
that was in accordance with the BET specific area 61
(195, 382 and 770 m2 g-1) and pore volume (0.62, 0.89 62
and 1.18 cm-3 g-1). Current density-potential curve of 63
HCDMS-1 was shown (Fig. 7E) and the current 64
density exhibited the typical increase with rotation 65
rate due to the shorted diffusion layer. The electron 66
transfer number (n) was analyzed on the basis of 67
Koutecky-Levich (KL) equations, a significant 68
increase could be observed with HCDMS-3 (n=2.9), 69
HCDMS-2 (n=3.8) and HCDMS-1 (n=4.0). 70
Furthermore, the durability, the methanol crossover 71
effect, and CO poisoning were investigated to 72
evaluate the properties of the HCDMSs (Fig. S5 in 73
the ESM). HCDMS-1 showed a better durability 74
with relative current of 79.2% than commercial Pt/C 75
with 70.8%. No obvious response for HCDMS-1 was 76
detected at 1000 s while methanol was added very 77
quickly, whereas a strong response was observed 78
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8 Nano Res.
for the Pt/C catalyst at the same condition. As 1
shown in Figure. S5 c, the HCDMS electrode was 2
insensitive to CO, whereas the Pt/C electrode was 3
rapidly poisoned under the same conditions. 4
We also investigated the electrocatalytic 5
properties of the nitrogen-doped hollow 6
carbonaceous nanospheres for oxygen reduction in 7
acid electrolyte. As shown in Fig. S6 (in the ESM), 8
the polarization curves for ORR in O2-saturated 0.1 9
M HClO4 on HCDMS-1 and commercial Pt/C 10
catalysts. HCDMS-1 exhibited high catalytic activity 11
toward ORR, with an onset potential at 0.723 V (vs. 12
SCE) and a 0.2 V overpotential as compared with 13
Pt/C. The higher overpotential in acid medium 14
supported the previous view that ORR activities of 15
nitrogen-doped carbon were higher in alkaline 16
medium than in acid medium [62]. 17
Figure 7 Cyclic voltammograms of (A) HCDMS-1, HCDMS-4 18
and HCDMS-5; (B) HCDMS-1, HCDMS-2 and HCDMS-3. 19
Linear sweep voltammograms on a glassy carbon rotating disk 20
electrode in O2-saturated 0.1 M KOH at a rotation rate of 1600 21
rpm (C) HCDMS-1, HCDMS-4 and HCDMS-5; (D) HCDMS-1, 22
HCDMS-2 and HCDMS-3; (E) LSV curves of ORR at various 23
rotation speeds at HCDMS-1 electrode; (F) Koutecky-Levich 24
plots for HCDMS-1, HCDMS-2, HCDMS-3 and 20 wt% Pt/C 25
at -0.60V. 26
27
4 Conclusion 28
29
In summary, we have demonstrated an easy and 30
effective route to synthesize N-doped HCDMSs 31
using carbohydrate-based derivative, i.e. GAH as 32
both carbon and nitrogen source. The approach 33
yielded N-doped HCDMSs with high surface areas 34
(770 m2 g-1), tailorable size and shell thickness, and 35
appropriate nitrogen content. Because of all these 36
superb features mentioned above, they could serve 37
as efficiently metal-free catalyst for the oxygen 38
reduction reaction both in alkaline and acidic 39
solutions. Importantly, we have presented a 40
cost-effective synthesis towards N-doped HCDMSs 41
based on sustainable biomass. Furthermore, the 42
HCDMSs show great promise for many 43
applications such as lithium ion batteries, 44
adsorbents, catalyst supports and drug delivery 45
carriers, and more works focusing on these aspects 46
are ongoing. 47
48
Acknowledgements 49
50
Financial support from the National Natural Science 51
Foundation of China (U1162124& 21376208), the 52
Zhejiang Provincial Natural Science Foundation for 53
Distinguished Young Scholars of China 54
(LR13B030001), the Specialized Research Fund for 55
the Doctoral Program of Higher Education 56
(J20130060), the Fundamental Research Funds for 57
the Central Universities, the Program for Zhejiang 58
Leading Team of S&T Innovation, the Partner 59
Group Program of the Zhejiang University and the 60
Max-Planck Society are greatly appreciated. 61
62
Electronic Supplementary Material: 63
Supplementary material (TEM and SEM images, 64
Powder XRD analysis of HCDMS-1, N2 65
adsorption/desorption isotherms, Current-time 66
response, the synthesis conditions and physical 67
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9 Nano Res.
properties, structural properties and elemental 1
analysis data) is available in the online version of 2
this article at 3
http://dx.doi.org/10.1007/s12274-***-****-* 4
5
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17
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Electronic Supplementary Material
Controlled synthesis of sustainable n-doped hollow
core mesoporous shell carbonaceous nanospheres
from biomass
Chuanlong Han, Shiping Wang, Jing Wang, Mingming Li, Jiang Deng, Haoran Li and Yong Wang()
Supporting information to DOI 10.1007/s12274-****-****-*
Figure S1. TEM and SEM images of SCDMS-1, SCDMS-2 and SCDMS-3.
Figure S2. Powder X-ray diffraction patterns of the HCDMS-1.
Figure S3. N2 adsorption/desorption isotherms of SCDMSs and HCDMSs.
Figure S4. Diameter distribution of HCDMSs.
Figure S5. Chronoamperometric response for ORR at HCDMS-1 and Pt/C electrodes.
Figure S6. Polarization curves for oxygen reduction in O2-saturated 0.1 M HClO4 solution.
Figure S7. (A) Cyclic voltammogram and (B) Linear sweep voltammogram of SCDMS-1.
Table S1. The synthesis conditions and physical properties.
Table S2. Structural properties of the SCDMSs.
Table S3. Elemental analysis data obtained for HCDMSs.
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Figure S1. (A) (C) and (D) TEM images of SCDMS-1, SCDMS-2 and SCDMS-3,
respectively, (B) SEM image of SCDMS-1.
Figure S2. Powder X-ray diffraction patterns of the HCDMS-1
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Figure S3. N2 adsorption/desorption isotherms of (A) SCDMS-1, SCDMS-2 and SCDMS-3; (B) HCDMS-1, HCDMS-2 and
HCDMS-3. Corresponding desorption pore size distributions of (C) SCDMS-1, SCDMS-2 and SCDMS-3; (D) HCDMS-1,
HCDMS-2 and HCDMS-3; (E) BET surface areas versus shell thickness; (F) BET surface areas versus average pore diameter.
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Figure S4. Diameter distribution of HCDMSs (Statistics on 100 spheres)
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Figure S5. Chronoamperometric response for ORR at HCDMS-1 and Pt/C electrodes at -0.3 V in O2-saturated 0.1 M KOH
at 1600 rpm (A) Durability evaluation for 20000s. (B) on addition of 3 vol% CH3OH after about 1000s. (C) on introduction
of CO (10 vol%) after about 200s.
Figure S6. Polarization curves for oxygen reduction in O2-saturated 0.1 M HClO4 solution on HCDMS-1 and 20 wt. % Pt/C;
Scan rate: 10 mV s-1; rotation rate: 1600 rpm.
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Figure S7. (A) Cyclic voltammogram and (B) Linear sweep voltammogram of SCDMS-1
As shown in Figure S7, featureless voltammetric currents within the potential range between -0.8
and 0.2 V were observed for SCDMS-1, which suggested that hard template SCDMS-1 didn’t have
any ORR activity.
Table S1. The synthesis conditions and physical properties.
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Table S2. Structural properties of the SCDMSs.
a. BJH desorption average pore diameter
Table S3. Elemental analysis data obtained for HCDMSs.
Address correspondence to [email protected]