Sub-5 nm Ultrasmall MetalâOrganic Framework Nanocrystals for

Subscriber access provided by Kaohsiung Medical University

Sub-5 Nanometer Ultrasmall Metal-Organic Framework Nanocrystals for Highly Efficient Electrochemical Energy Storage Peitao Xiao, Fanxing Bu, Ranran Zhao, Mohamed F. Aly Aboud, Imran Shakir, and Yuxi Xu ACS Nano, Just Accepted Manuscript • DOI: 10.1021/acsnano.8b01488 • Publication Date (Web): 20 Mar 2018 Downloaded from http://pubs.acs.org on March 20, 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 23 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 Nano

Sub-5 Nanometer Ultrasmall Metal-Organic Framework Nanocrystals for Highly Efficient Electrochemical Energy Storage Peitao Xiao,† Fanxing Bu,† Ranran Zhao,† Mohamed F. Aly Aboud, ‡ Imran Shakir*,‡ and Yuxi Xu*,† †

State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular

Science, Fudan University, Shanghai 200433, China ‡

Sustainable Energy Technologies Center, College of Engineering, King Saud University,

Riyadh 11421, Kingdom of Saudi Arabia ABSTRACT: Synthesis of ultrasmall metal-organic frameworks (MOFs) nanoparticles has been widely recognized as a promising route to greatly enhance their properties but remains a considerable challenge. Herein, we report one facile and effective spatial-confined thermal pulverization strategy to successfully transform bulk Co-MOFs particles into sub-5 nm nanocrystals encapsulated within N-doped carbon/graphene (NC/G) by using conducting polymer coated Co-MOFs/graphene oxide as precursors. This strategy involves a feasible mechanism: calcination of Co-MOFs at proper temperature in air induces the partial thermal collapse/distortion of the framework, while the uniform coating of conducting polymer can significantly improve the decomposition temperature and maintain the component stability of

ACS Paragon Plus Environment

1

ACS Nano 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 23

Co-MOFs, thus leading to the pulverization of bulk Co-MOFs particles into ultrasmall nanocrystals without oxidation. The pulverization of Co-MOFs significantly increases the contact area between Co-MOFs with electrolyte and shortens the electron and ion transport pathway. Therefore, the sub-5 nm ultrasmall MOFs nanocrystals-based composites deliver an ultrahigh reversible capacity (1301 mAh g-1 at 0.1 A g-1), extraordinary rate performance (494 mAh g-1 at 40 A g-1) as well as outstanding cycling stability (98.6% capacity retention at 10 A g-1 after 2000 cycles), which is the best performance achieved in all reported MOFs-based anodes for lithium-ion batteries. KEYWORDS:

metal-organic

frameworks,

pulverization,

ultrasmall

nanocrystals,

electrochemical energy storage, lithium-ion battery. Metal-organic frameworks, also known as porous coordination polymers, have been extensively investigated as a new class of inorganic-organic hybrid materials. Because of their tunable pore sizes and structures, high specific surface and pore volume, MOFs have recently shown their unique advantages and great potentials in energy storage and conversation, such as supercapacitors,1 lithium-ion batteries (LIBs),2 lithium-sulfur batteries,3-6 lithium-oxygen batteries,7 CO2 reduction,8, 9 oxygen evolution and reduction reactions,10-12 etc.13, 14 Meanwhile, when the size of materials is reduced to nanoscale dimension, physicochemical properties can change dramatically.15-19 Owning to the exceptional size-dependent properties, nanomaterials have been widely explored in various areas,15-19 including the energy-related application.20, 21 Recent studies have demonstrated that compared with bulk particle, higher specific surface and more active sites can be obtained by decreasing the size of MOFs to nanoscales (usually with dimensional scales larger than 50 nm), which can highly enhance the electrochemical process, leading to excellent electrochemical performance.2, 22-25 However, the investigation of ultrasmall


2

Page 3 of 23 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 Nano

MOFs nanoparticles with size down to sub-5 nm in energy storage and conversion has not yet been explored so far due to lack of efficient synthesis method. Although extensive studies have been conducted to fabricate some other ultrasmall nanomaterials, among which laser synthesis and processing,26 electrochemical,27 fast Joule heating,28 atomic and molecular layer deposition,29 and etc. were investigated, these methods are not applicable for MOFs because of the instabilities of MOFs under extreme conditions or different intrinsic molecular structures of MOFs. Therefore, a facile, low-cost and scalable approach to fabricate ultrasmall MOFs nanoparticles is of great challenge yet urgently desired.

Figure 1. Schematic illustration of spatial-confined pulverization process: (a) GC, (b) GCP, (c) GCP350, (d) GC350. Herein, we report a simple and environmental friendly spatial-confined pulverization method to fabricate sub-5 nm ultrasmall MOFs nanocrystals through calcinations in air. We first


3

ACS Nano 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 4 of 23

grow Co-MOFs particles (average size of ~100 nm) uniformly on graphene oxide (GO) sheets to obtain GO/Co-MOFs (GC) composites (see detail information in experimental section, Figure S1a and c) through the coordination and electrostatic interaction.30-32 Then, compactly coating of conducting polypyrrole (PPy) on GC surface by in-situ polymerization was conducted to obtain GO/Co-MOFs/PPy (GCP) composites (Figure S1b). Because of the protective PPy layers, after thermal treatment of GCP at 350 °C in air, bulk MOFs particles were pulverized into ultrasmall nanocrystals (average diameter of ~4.2 nm) with the surrounding PPy and GO layers converted into N-doped carbon/graphene (NC/G) simultaneously. However, without the coating of PPy, Co-MOFs particles transform into metal oxide instead, as schematically shown in Figure 1. To investigate the effect of ultrasmall MOFs particles on electrochemical energy storage, the ultrasmall Co-MOFs nanocrystals encapsulated in NC/G (denoted as GCP350) by simple calcination of GCP at 350 °C in air were explored as binder-free anodes for lithium-ion batteries. The entire GCP350 anodes achieved ultrahigh reversible capacity (1301 mAh g-1 at 0.1 A g-1), extraordinary rate performance (494 mAh g-1 at 40 A g-1), and excellent long-term cycling stability (98.6% retention at 10 A g-1 over 2000 cycles), much better than the non-pulverized MOF/G composite and representing the best performance achieved in all MOFs-based anodes ever reported. RESULTS AND DISCUSSION Morphological evolutions of ultrasmall Co-MOFs nanocrystals were firstly investigated by scanning electron microscope (SEM) and transmission electron microscopy (TEM). As shown in Figure 2a, PPy was homogenously coated on GC, and bulk Co-MOFs particles with average diameter of 80-110 nm (Figure S2) were encapsulated by the GO and PPy layers. The elemental mapping images in Figure S1d-j also show the homogenous coating of PPy on Co-MOFs. After


4

Page 5 of 23 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 Nano

thermal treatment of GCP at 350 °C for 2h in air, the Co-MOFs particles were homogeneously distributed and well encapsulated by NC/G, as shown in Figure 2b and Figure S3. In addition, HRTEM images (Figure 2c and 2d) show that the Co-MOFs particles were surrounded by ultrathin layers of NC/G. Interestingly, the individual bulk Co-MOFs particle in GCP was pulverized into plenty of ultrasmall nanocrystals (average diameter of ~4.2 nm, the insert in Figure 2c) with little void space between each other. The lattice fringes with a spacing about 0.25 nm is assigned to (400) plane of Co-MOFs (JCPDS#77-1161, Figure 2e). The rings in the selected area electron diffraction (SAED) pattern (Figure 2f) also indicate the intactness of ultrasmall Co-MOFs nanocrystals. The homogenous element mapping images of C, Co, and N in Figure 2g-i also imply these spatial-confined pulverized ultrasmall Co-MOFs particles are uniformly distributed and tightly wrapped by NC/G.


5

ACS Nano 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 6 of 23

Figure 2. TEM images of GCP (a) and GCP350 (b); (c, d) HRTEM images of GCP350 (the insert is histogram of size distribution of nanocrystals), and the corresponding lattice structure (e), SAED pattern (f), and element mapping images (g-i). In order to fully understand the formation of pulverized ultrasmall Co-MOFs nanocrystals, detailed structural characterizations were carefully carried out by X-ray diffraction (XRD), and Fourier transform infrared spectra (FTIR). As shown in Figure 3a, in all Co-MOFs, GC, GCP and GCP350, these four dominant peaks at 17.2, 24.5, 34.9 and 39.4°, are well indexed to neat Co-MOFs (JCPDS#77-1161), demonstrating that Co-MOFs in GCP350 still existed even after calcinations at 350 °C in air. For GCP350, peak intensity decreased and full width at half maximum (FWHM) increased, which may result from the pulverization of bulk Co-MOFs into ultrasmall nanocrystals according to Scherrer Formula.8, 33 As shown in the FTIR results (Figure 3b), these two dominant peaks in 2176 cm-1 and 460 cm-1 (enlarged spectra in Figure S4), corresponding to the stretching vibrations of CN- and deformation of Co-C bond, respectively, also demonstrated the intactness of Co-MOFs in GCP350.34, 35 In addition, PPy was partially decomposed into N-doped carbon , and GO was reduced to graphene during calcinations, which were confirmed by thermo gravimetric analysis (TGA) in Figure S6.36 The conversation of PPy into N-doped carbon was also confirmed by the N 1s X-ray photoelectron spectroscopy (XPS) spectra in Figure S5. Structural evolution of neat GC under calcinations at 350 °C in air (denoted as GC350) was also investigated. As shown in Figure 3a, characteristic peaks of Co-MOFs disappeared, while these of Co3O4 (JCPDS#80-1553) emerged, indicating the transformation of Co-MOFs into metal oxide particles (Figure S7) without the protection of PPy. The appearance of new peaks (573 cm-1 and 667 cm-1) in Figure 3b also demonstrate the transformation in GC350.37 At higher calcination temperature (400 °C), Co-MOFs in GCP also transformed into


6

Page 7 of 23 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 Nano

metal oxide (Figure S8 and S9). At relatively low calcination temperature (250 °C), the bulk CoMOFs particles remain intact without any pulverization (Figure S10). In order to further understand the mechanism of space-confined pulverization, TGA of neat Co-MOFs, GCP and GCP350 were carried out. As shown in Figure S11 and S12, the decomposition temperature (368 °C) of Co-MOFs in GCP is much higher than that of neat Co-MOFs (325 °C). Meanwhile, GCP350 also began to transform into metal oxide at about 368 °C, implying Co-MOFs did not convert into metal oxide during the pulverization process of GCP at 350 °C. Based on these results, we propose that calcination of GCP at proper temperature may induce the partial collapse/distortion of the framework of Co-MOFs particles,38 while the uniform coating of PPy can significantly improve the decomposition temperature and maintain the component stability of Co-MOFs during calcinations in air, thus leading to the pulverization of bulk Co-MOFs particles in GCP into ultrasmall nanoparticles without oxidation during this spatial-confined pulverization process. It is noteworthy that the significant increase of decomposition temperature is induced by the tight coating of PPy, which may benefits from the good affinity to other materials and high flexibility of this conductive polymer.39, 40

Figure 3. (a) XRD patterns and (b) FTIR spectra of Co-MOFs, GC, GCP, GCP350 and GC350.


7

ACS Nano 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 8 of 23

Our GCP350 nanocomposites showed a hierarchical structure with ultrasmall Co-MOFs nanocrystals encapsulated by interconnected ultrathin conductive layers of NC/G, which promoted us to further explore them as binder-free anodes for lithium-ion batteries. For comparison, the GC350 and GCP250 were also tested (Figure S13) to understand the structureproperty relationship. Electrochemical performance of GCP350 was firstly investigated by galvanostatic discharge-charge tests between 0.01 and 3 V at 0.2 A g-1. As shown in Figure 4a, GCP350 anodes delivered an initial discharge capacity of 1978 mAh g-1 (calculated on the whole electrode), and a reversible charge capacity of 1198 mAh g-1 with relatively low initial Coulombic efficiency (CE) of 60.6%, caused by electrolyte decomposition and formation of solid-electrolyte interphase (SEI).20 Meanwhile, the discharge-charge curves almost overlapped for 2nd, 5th, and 10th cycles, demonstrating the excellent cycling stability of GCP350. Cycling performance was further tested at 0.2 A g-1 (Figure 4b). The capacity of GCP350 was 1201 mAh g-1 with CE above 95% in the second cycle. After 100 cycles, the capacity of GCP350 anodes still retained 1192 mAh g-1 with CE of ~99%, which is much better than that of GCP250 and GC350. Rate performance of GCP350 anodes was evaluated at current densities from 0.1 A g-1 to 40 A g-1. Figure 4c shows the typical galvanostatic discharge-charge curves of GCP350 under different current densities, and the reversible capacities of GCP350 are 1301, 1188, 1060, 987, 906, 801, 701, and 596 mAh g-1 at current densities of 0.1, 0.2, 0.5, 1, 2, 5, 10, and 20 A g-1, respectively, far surpassing those of GCP250 and GC350 (Figure 4d). Even at a super-high current density of 40 A g-1, which has never been reported for MOFs-based anodes, the GCP350 can still achieve an impressive capacity of 494 mAh g-1, demonstrating the superior rate performance of GCP350. Moreover, the reversible capacity of GCP350 anodes recovered to 1255 mAh g-1 when current density returned to 0.1 A g-1, indicating excellent structural stability


8

Page 9 of 23 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 Nano

of GCP350. To the best of our knowledge, the capacity and the rate performance of GCP350 are significantly higher than all MOFs-based anodes for LIBs reported recently (Figure 4e and Table S1).41-45 In addition, we have also tested the control sample without Co-MOFs (Figure S14) and confirmed the extraordinary electrochemical performance of GCP350 was mainly contributed by the ultrasmall Co-MOFs nanocrystals. The electrochemical processes of these electrodes were further investigated and compared by electrochemical impedance spectroscopy (EIS). As shown in Figure 4f, both the charge-transfer resistance in the high-to-medium-frequency region and Warburg impedance in low-frequency region of GCP350 are smaller than those of GCP250 and GC350, indicating that ultrasmall Co-MOFs nanocrystals provide abundant contact area for electrolyte to access active material, fastening charge transfer and enhance Li-ion diffusion, leading to the dramatic enhancement of electrochemical performance of GCP350.


9

ACS Nano 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 10 of 23

Figure 4. Electrochemical characterizations of GCP350, GCP250, and GC350 anodes. (a) charge-discharge curves of GCP350 anodes at 0.2 A g-1; (b) cycling performance of GCP350, GCP250, and GC350 anodes at 0.2 A g-1; (c) charge-discharge curves of GCP350 anodes at different current densities; (d) rate performance of GCP350, GCP250, and GC350 anodes; (e) comparison of GCP350 and other representative MOFs-based electrodes; (f) EIS plots of GCP350, GCP250 and GC350 anodes; (g) cycling performance of GCP350 anodes at 5 and 10 A g-1 for 2000 cycles. The long-term cycling performance at high current densities was further investigated, as shown in Figure 4g. The GCP350 anodes delivered a capacity of 795 mAh g-1 at the second cycle (the initial discharge capacity is neglected because of the formation of SEI during the first discharge process), and remained 92.9% (739 mAh g-1) after 2000 cycles at 5 A g-1. More importantly, the capacity retention of GCP350 anodes at 10 A g-1 is 98.6%, with a decay rate of only 0.0007% per cycle. At such high current density, GCP350 could be fully charged in less than 5 minutes, which makes them of great importance in practical applications. To better understand the excellent electrochemical performance, reaction kinetics was analyzed by cyclic voltammetry (CV) tests at different sweeping rates from 0.2 to 10 mV/s (Figure 5a) based on the following equations: i = α νb, where i is the peak current, ν is the sweep rate, α is a constant, and b is an adjustable parameter.46-48 A b value of 1 indicates that the electrochemical reaction is non-Faradaic capacitive-controlled. When b = 0.5, it indicates that current is limited by semi-infinite linear diffusion.46-48 As shown in Figure 5b, when scan rate is below 1 mV/s, a b value of 0.89 for oxidation peak in Figure 5a can be calculated, indicating the electrochemical process of GCP350 is related to both capacitive and diffusion behaviors. When scan rate is above 1 mV/s, b value decreases from 0.89 to 0.8, implying an increased high-rate


10

Page 11 of 23 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 Nano

diffusion-limited process of GCP350 at high current densities, which may results from the increase of resistance at high rates.46

Figure 5. (a) CV curves at different scan rates from 0.2 to 10 mV/s; (b) b-value at different scan rates, calculated from peak current and scan rate from (a); (c) separation of the contribution of capacitive- and diffusion-controlled current to the total current at 0.2 mV/s; (d) contribution ratio of capacitive- and diffusion-controlled capacities at different scan rates; (e) schematic illustration of enhanced ion/electron transport in pulverized ultrasmall MOF nanocrystals.


11

ACS Nano 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 12 of 23

It is well known that surface-controlled reaction is favorable to obtain excellent high-rate performance. Hence, the contribution of surface capacitive-controlled and diffusion-controlled process to the capacity of GCP at different sweep rates was further investigated according to the following equations: i = k1ν + k2ν1/2, where surface capacitive- and diffusion-controlled contribution is weighted by k1 and k2, respectively.46 As shown in Figure 5c, the normalized contribution ratio of capacitive-controlled capacity (the red zone) at 0.2 mV/s is about 49.6%, while that of diffusion-controlled capacity is about 50.4%. By gradually increasing scan rate, the capacitive-controlled contribution ratio improves significantly from 50.4% at 0.2 mV/s to 91.9% at 10 mV/s, as shown in Figure 5d. The enhanced capacitive-controlled behavior mainly results from the ultrasmall size of Co-MOFs nanocrystals and ultrathin carbonaceous layers49 since ultrasmall Co-MOFs nanocrystals provide abundant contact area for electrolyte to access active material (the surface area increased from 138 m2 g-1 for GCP to 392 m2 g-1 for GCP350 during pulverization based on N2 adsorption-desorption analysis in Figure S15), fastening charge transfer and enhance Li-ion diffusion, as schematically shown in Figure 5e. Based on the above discussion, the excellent electrochemical performance of GCP350 can be attributed to the following points. First, the spatial-confined pulverization of MOFs into ultrasmall nanocrystals provides large contact area for electrolyte with active materials, significantly shortening the Li-ion and electron diffusion distance. Meanwhile, ultrasmall CoMOFs with high surface area, together with two-dimensional ultrathin NC/G layers, provide sufficient accessible sites for Li-ion storage. Second, the void space between ultrasmall CoMOFs nanocrystals and the robust coating layer of NC/G can effectively buffer the volume change, and therefore alleviate the capacity loss during the long-term cycling. Third, the interconnected conductive NC/G layer can prompt electron transportation as a whole network.


12

Page 13 of 23 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 Nano

Owning to the above synergetic merits, the GCP350 anodes exhibit significantly enhanced lithium-storage performance compared to previous MOFs-based anodes. CONCLUSIONS In conclusion, we report a facile thermal-assisted spatial-confined pulverization method to fabricate ultrasmall Co-MOFs nanocrystals with diameter down to sub-5 nm. When used as freestanding anodes for LIB, the GCP350 exhibited ultrahigh reversible capacities (1301 mAh g-1 at 0.1 A g-1), excellent rate performance (494 mAh g-1 at 40 A g-1) and superior long-term cycling stability (98.6% capacity retention at 10 A g-1 after 2000 cycles), which is the best performance for MOFs-based LIB anodes so far. This versatile space-confined pulverization strategy can also be applied to other MOFs with suitable protective layers under proper temperatures and may provide a universal route to large-scale synthesis of ultrasmall functional MOFs nanocrystals with promising applications in energy storage and conversion and beyond. EXPERIMENTAL SECTION Synthesis of Graphene oxide (GO): Natural graphite powder (325 mesh, Aladdin, 99.95% metal basis) was used to synthesize GO via modified Hummers’ method. All the other chemicals were purchased from Sigma or Aladdin, and used without purification. Synthesis of GO-Co-MOFs-polypyrrole (GCP): Firstly, 40 mg GO and 0.2 ml potassium hexacyanocobaltate (Co3[Co(CN)6]2, 0.5M) were dissolved in 80 ml deionized water, and then mixed under magnetic stirring and ultrasonic for 10 and 5 min, respectively. 2 ml cobalt chloride (CoCl2, 0.5M) was poured into the above solution, followed by stirring for 1 h. Secondly, 120 mg ammonium persulfate ((NH4)2S2O8) and 120 µl pyrrole were added into the above solution


13

ACS Nano 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 14 of 23

subsequently, followed by constantly stirring overnight for coating of polypyrrole (PPy). Thirdly, the solution was centrifuged three times and then freeze-dried overnight to get GCP aerogel. Graphene oxide/Co-MOFs (GC) aerogel and Graphene oxide/PPy (GP) were obtained by the the same procedures without the addition of pyrrole, and potassium hexacyanocobaltate/ cobalt chloride, respectively . Preparation of GCP350 composites: The GCP350 nanocomposites were obtained by one-step thermal treatment of GCP aerogel in air. Typically, GCP aerogel was heated gradually to 350 °C at a rate of 10 °C/min, and maintained for 2h in air. GC350 and GP350 was obtained by calciantion of GC and GP aerogel under the same contion. GCP250 was prepared by calcination of GCP at 250 °C for 2 h in air. Characterizations: The morphology characterizations were performed on field emission scanning eletron microscope (FESEM, Zeiss Ultra-55) and Transmission electron microscope (TEM, FEI Tecnai G2 20TWIN, 200 kV). PANalytical X’ pert PRO X-ray diffraction (XRD, Cu Kα) was used to complete the XRD analysis from 10° to 80°. Pyris 1 TGA was used to carry out Thermo gravimetric analysis (TGA) tests at a heating rate of 10 °C/min in air. Fourier Transform Infrared spectra (FTIR) were measured on Thermofisher Nicolet 6700 Fourier transformation infrared spectrometer. X-ray photoelectron spectroscopy (XPS) was performed on PHI 5000C ESCA System. Autosorb IQ Gas Sorption System was used to conduct BET test at 77 K. Electrochemical Characterization: The free-standing GCP350 films obtained by compression of GCP350 aerogel were used directly as anodes for lihitum-ion batteries (LIBs). The areal mass loading of GCP350 was ~1.5 mg cm-2. LIBs were assembled in an argon-filled glove box with Cellard 2400 and metallic lithium, as separator and counter eletrode, respectively. 1 M LiPF6 in


14

Page 15 of 23 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 Nano

EC: DMC (1:1 by volume ratio) was used as the electrolyte. The galvanostatic experiments were tested on a battery testing system (LAND, Wuhan China) in the voltage window from 0.01 V to 3 V at different current densities. CHI 760D electrochemical workstation was used to perform electrochemical impedance spectroscopy (EIS) in the frequency range of 100 kHz to 0.01 Hz and cyclic voltammy (CV) curves in the potential range of 0.01-3 V at the different scanning rates. ASSOCIATED CONTENT Supporting Information. The supporting information is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected] *E-mail: [email protected] Author Contributions P. T. Xiao and F. X. Bu contributed equally. ACKNOWLEDGMENT We acknowledge the support by the National Natural Science Foundation of China (51673042), the Young Elite Scientist Sponsorship Program by CAST (2017QNRC001), the Program for Professor of Special Appointment (Eastern Scholar) at Shanghai Institutions of Higher Learning (TP2015002), and China Postdoctoral Science Foundation (2017M611445). The authors would like extend their sincere appreciation to the Deanship of Scientific Research at King Saud University for its funding of this research through the Research Group Project no RGP-VPP-312.


15

ACS Nano 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 16 of 23

REFERENCES 1. Choi K. M.; Jeong H. M.; Park J. H.; Zhang Y.-B.; Kang J. K.; Yaghi O. M. Supercapacitors of Nanocrystalline Metal Organic Frameworks. ACS Nano 2014, 8, 7451–7457. 2. Mahmood N.; Tang T.; Hou Y. Nanostructured Anode Materials for Lithium Ion Batteries: Progress, Challenge and Perspective. Adv. Energy Mater. 2016, 6, 1600374. 3. Su D.; Cortie M.; Fan H.; Wang G. Prussian Blue Nanocubes with an Open Framework Structure Coated with PEDOT as High-Capacity Cathodes for Lithium-Sulfur Batteries. Adv. Mater. 2017, 29, 1700587. 4. Liu Y.; Li G.; Fu J.; Chen Z.; Peng X. Strings of Porous Carbon Polyhedrons as Self-Standing Cathode Host for High-Energy-Density Lithium–Sulfur Batteries. Angew. Chem. Int. Ed. 2017, 129, 6272-6276. 5. Mao Y.; Li G.; Guo Y.; Li Z.; Liang C.; Peng X.; Lin Z. Foldable Interpenetrated MetalOrganic Frameworks/Carbon Nanotubes Thin Film for Lithium-Sulfur Batteries. Nat. Commun. 2017, 8, 14628. 6. He J.; Chen Y.; Lv W.; Wen K.; Xu C.; Zhang W.; Li Y.; Qin W.; He W. From Metal-Organic Framework to Li2S@C-Co-N Nanoporous Architecture: A High-Capacity Cathode for LithiumSulfur Batteries. ACS Nano 2016, 10, 10981-10987. 7. Liu Y.; He P.; Zhou H. Rechargeable Solid-State Li-Air and Li-S Batteries: Materials, Construction, and Challenges. Adv. Energy Mater. 2017, 8, 1701602. 8. Gao D.; Zhou H.; Wang J.; Miao S.; Yang F.; Wang G.; Wang J.; Bao X. Size-Dependent Electrocatalytic Reduction of CO2 Over Pd Nanoparticles. J. Am. Chem. Soc. 2015, 137, 42884291.


16

Page 17 of 23 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 Nano

9. Liang Z.; Qu C.; Guo W.; Zou R.; Xu Q. Pristine Metal-Organic Frameworks and Their Composites

for

Energy

Storage

and

Conversion.

Adv.

Mater.

2017,

DOI:

10.1002/adma.201702891. 10. Liu S.; Wang Z.; Zhou S.; Yu F.; Yu M.; Chiang C. Y.; Zhou W.; Zhao J.; Qiu J. MetalOrganic-Framework-Derived Hybrid Carbon Nanocages as A Bifunctional Electrocatalyst for Oxygen Reduction and Evolution. Adv. Mater. 2017, 29, 1700874. 11. Yilmaz G.; Yam K. M.; Zhang C.; Fan H. J.; Ho G. W. In Situ Transformation of MOFs into Layered Double Hydroxide Embedded Metal Sulfides for Improved Electrocatalytic and Supercapacitive Performance. Adv. Mater. 2017, 29, 1606814. 12. Zeng M.; Liu Y.; Zhao F.; Nie K.; Han N.; Wang X.; Huang W.; Song X.; Zhong J.; Li Y. Metallic Cobalt Nanoparticles Encapsulated in Nitrogen-Enriched Graphene Shells: Its Bifunctional Electrocatalysis and Application in Zinc-Air Batteries. Adv. Funct. Mater. 2016, 26, 4397-4404. 13. He J.; Lv W.; Chen Y.; Wen K.; Xu C.; Zhang W.; Li Y.; Qin W.; He W. TelluriumImpregnated Porous Cobalt-Doped Carbon Polyhedra as Superior Cathodes for LithiumTellurium Batteries. ACS Nano 2017, 11, 8144-8152. 14. He J.; Lv W.; Chen Y.; Xiong J.; Wen K.; Xu C.; Zhang W.; Li Y.; Qin W.; He W. Threedimensional Hierarchical C-Co-N/Se Derived from Metal-Organic Framework as Superior Cathode for Li-Se Batteries. J. Power Sources 2017, 363, 103-109. 15. Atwater H. A.; Polman A. Plasmonics for Improved Photovoltaic Devices. Nat. Mater. 2010, 9, 205-213.


17

ACS Nano 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 18 of 23

16. Maier S. A.; Kik P. G.; Atwater H. A.; Meltzer S.; Harel E.; Koel B. E.; Requicha A. A. Local Detection of Electromagnetic Energy Transport Below the Diffraction Limit in Metal Nanoparticle Plasmon Waveguides. Nat. Mater. 2003, 2, 229-232. 17. Li J. F.; Zhang Y. J.; Ding S. Y.; Panneerselvam R.; Tian Z. Q. Core-Shell NanoparticleEnhanced Raman Spectroscopy. Chem. Rev. 2017, 117, 5002-5069. 18. Liu Y.; Dong X.; Chen P. Biological and Chemical Sensors Based on Graphene Materials. Chem. Soc. Rev. 2012, 41, 2283-2307. 19. Vaghari H.; Jafarizadeh-Malmiri H.; Mohammadlou M.; Berenjian A.; Anarjan N.; Jafari N.; Nasiri S. Application of Magnetic Nanoparticles in Smart Enzyme Immobilization. Biotechnol. Lett. 2016, 38, 223-233. 20. Li D.; Yang D.; Yang X.; Wang Y.; Guo Z.; Xia Y.; Sun S.; Guo S. Double-Helix Structure in Carrageenan–Metal Hydrogels:A General Approach to Porous Metal Sulfides/Carbon Aerogels with Excellent Sodium-Ion Storage. Angew .Chem. Int. Ed. 2016, 55, 15925 -15928. 21. Xiao P.; Bu F.; Yang G.; Zhang Y.; Xu Y. Integration of Graphene, Nano Sulfur, and Conducting Polymer into Compact, Flexible Lithium-Sulfur Battery Cathodes with Ultrahigh Volumetric Capacity and Superior Cycling Stability for Foldable Devices. Adv. Mater. 2017, 29, 1703324. 22. Zhao S.; Wang Y.; Dong J.; He C.-T.; Yin H.; An P.; Zhao K.; Zhang X.; Gao C.; Zhang L.; Lv J.; Wang J.; Zhang J.; Khattak A. M.; Khan N. A.; Wei Z.; Zhang J.; Liu S.; Zhao H.; Tang Z. Ultrathin Metal–Organic Framework Nanosheets for Electrocatalytic Oxygen Evolution. Nat. Energy 2016, 1, 16184.


18

Page 19 of 23 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 Nano

23. Shi C.; Gao Y.; Liu L.; Song Y.; Wang X.; Liu H.-J.; Liu Q. Nanoscale Zinc-Based MetalOrganic Framework with High Capacity for Lithium-Ion Batteries. J. Nanopart. Res. 2016, 18, 371. 24. Hu X.; Lou X.; Li C.; Ning Y.; Liao Y.; Chen Q.; Mananga E. S.; Shen M.; Hu B. Facile Synthesis of the Basolite F300-like Nanoscale Fe-BTC Framework and Its Lithium Storage Properties. RSC Adv. 2016, 6, 114483-114490. 25. Sun H.; Miyazaki S.; Tamamitsu H.; Saitow K. One-Pot Facile Synthesis of A Concentrated Si Nanoparticle Solution. Chem. Commun. 2013, 49, 10302-10304. 26. Zhang D.; Gokce B.; Barcikowski S. Laser Synthesis and Processing of Colloids: Fundamentals and Applications. Chem. Rev. 2017, 117, 3990-4103. 27. Wang H.; Lee H. W.; Deng Y.; Lu Z.; Hsu P. C.; Liu Y.; Lin D.; Cui Y. Bifunctional NonNoble Metal Oxide Nanoparticle Electrocatalysts through Lithium-induced Conversion for Overall Water Splitting. Nat. Commun. 2015, 6, 7261. 28. Chen Y.; Egan G. C.; Wan J.; Zhu S.; Jacob R. J.; Zhou W.; Dai J.; Wang Y.; Danner V. A.; Yao Y.; Fu K.; Wang Y.; Bao W.; Li T.; Zachariah M. R.; Hu L. Ultra-fast Self-Assembly and Stabilization of Reactive Nanoparticles in Reduced Graphene Oxide Films. Nat. Commun. 2016, 7, 12332. 29. Van Bui H.; Grillo F.; van Ommen J. R. Atomic and Molecular Layer Deposition: Off the Beaten Track. Chem. Commun. 2016, 53, 45-71. 30. Bu F.; Feng X.; Jiang T.; Shakir I.; Xu Y. One Versatile Route to Three-Dimensional Graphene Wrapped Metal Cyanide Aerogels for Enhanced Sodium Ion Storage. Chem. Eur. J. 2017, 23, 8358–8363.


19

ACS Nano 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 20 of 23

31. Jiang T.; Bu F.; Feng X.; Shakir I.; Hao G.; Xu Y. Porous Fe2O3 Nanoframeworks Encapsulated Within Three-Dimensional Graphene as High-Performance Flexible Anode for Lithium-Ion Battery. ACS Nano 2017, 11, 5140-5147. 32. Bu F.-X.; Xiao P.; Chen J.; Aly Aboud M. F.; Shakir I.; Xu Y. Phase Separation in MOF: One Effective Route to Construct Core-shell FeS@Carbon Nanocomposite Encapsulated in Three-Dimensional Graphene As Flexible High-Performance Anode for Sodium-Ion Battery. J. Mater. Chem. A 2018, DOI: 10.1039/c7ta11111h. 33. Patterson A. L. The Scherrer Formula for X-Ray Particle Size Determination. Phys. Rev. 1939, 56, 978-982. 34. Xiong P.; Zeng G.; Zeng L.; Wei M. Prussian Blue Analogues Mn[Fe(CN)6]0.6667.nH2O Cubes As An Anode Material for Lithium-Ion Batteries. Dalton Trans. 2015, 44, 16746-16751. 35. Nie P.; Shen L.; Luo H.; Ding B.; Xu G.; Wang J.; Zhang X. Prussian Blue Analogues: A New Class of Anode Materials for Lithium Ion Batteries. J. Mater. Chem. A 2014, 2, 5852-5857. 36. Wang Z. L.; Xu D.; Huang Y.; Wu Z.; Wang L. M.; Zhang X. B. Facile, Mild and Fast Thermal-decomposition Reduction of Graphene Oxide in Air and Its Application in HighPerformance Lithium Batteries. Chem. Commun. 2012, 48, 976-978. 37. Xu J.; Wu J.; Luo L.; Chen X.; Qin H.; Dravid V.; Mi S.; Jia C. Co3O4 Nanocubes Homogeneously Assembled on Few-layer Graphene for High Energy Density Lithium-Ion Batteries. J. Power Sources 2015, 274, 816-822. 38. S. K. S.; R. L. J. Hydrogen Storage in the Dehydrated Prussian Blue Analogues M3[Co(CN)6]2. J. Am. Chem. Soc. 2005, 127, 6506-6507. 39. Kim J.; Kim J. H.; Ariga K. Redox-Active Polymers for Energy Storage Nanoarchitectonics. Joule 2017, 1, 739-768.


20

Page 21 of 23 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 Nano

40. Kim J.; Lee J.; You J.; Park M.-S.; Hossain M. S. A.; Yamauchi Y.; Kim J. H. Conductive Polymers for Next-generation Energy Storage Systems: Recent Progress and New Functions. Mater. Horiz. 2016, 3, 517-535. 41. Li C.; Lou X.; Yang Q.; Zou Y.; Hu B. Remarkable Improvement in the Lithium Storage Property of Co2(OH)2 BDC MOF by Covalent Stitching to Graphene and the Redox Chemistry Boosted by Delocalized Eelectron Spins. Chem. Eng. J. 2017, 326, 1000-1008. 42. Song H.; Shen L.; Wang J.; Wang C. Reversible Lithiation–Delithiation Chemistry in Cobalt Based Metal Organic Framework Nanowire Electrode Engineering for Advanced Lithium-ion Batteries. J. Mater. Chem. A 2016, 4, 15411-15419. 43. Dong C.; Xu L. Cobalt- and Cadmium-Based Metal-Organic Frameworks As HighPerformance Anodes for Sodium Ion Batteries and Lithium Ion Batteries. ACS Appl. Mater. Interfaces 2017, 9, 7160-7168. 44. Wei T.; Zhang M.; Wu P.; Tang Y.-J.; Li S.-L.; Shen F.-C.; Wang X.-L.; Zhou X.-P.; Lan Y.-Q. POM-Based Metal-organic Framework/Reduced Graphene Oxide Nanocomposites with Hybrid Behavior of Battery-Supercapacitor for Superior Lithium Storage. Nano Energy 2017, 34, 205-214. 45. He S.; Li Z.; Ma L.; Wang J.; Yang S. Graphene Oxide-Templated Growth of MOFs with Enhanced Lithium-Storage Properties. New J. Chem. 2017, 41, 14209-14216. 46. Lou P.; Cui Z.; Jia Z.; Sun J.; Tan Y.; Guo X. Monodispersed Carbon-Coated Cubic NiP2 Nanoparticles Anchored on Carbon Nanotubes as Ultra-Long-Life Anodes for Reversible Lithium Storage. ACS Nano 2017, 11, 3705-3715.


21

ACS Nano 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 22 of 23

47. Sun J.; Lv C.; Lv F.; Chen S.; Li D.; Guo Z.; Han W.; Yang D.; Guo S. Tuning the Shell Number of Multi-Shelled Metal Oxide Hollow Fibers for Optimized Lithium Ion Storage. ACS Nano 2017, 11, 6168-6193. 48. Augustyn V.; Come J.; Lowe M. A.; Kim J. W.; Taberna P. L.; Tolbert S. H.; Abruna H. D.; Simon P.; Dunn B. High-Rate Electrochemical Energy Storage through Li+ Intercalation Pseudocapacitance. Nat. Mater. 2013, 12, 518-522. 49. Yang L.; Li X.; He S.; Du G.; Yu X.; Liu J.; Gao Q.; Hu R.; Zhu M. Mesoporous Mo2C/Ndoped Carbon Heteronanowires As High-Rate and Long-Life Anode Materials for Li-Ion Batteries. J. Mater. Chem. A 2016, 4, 10842-10849.


22

Page 23 of 23 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 Nano

Table of Graphic


23

Sub-5 nm Ultrasmall MetalâOrganic Framework Nanocrystals for

Recommend Documents

Sub-5 nm Ultrasmall MetalâOrganic Framework Nanocrystals for