CoxSy@S,N-Codoped Porous Carbon

Subscriber access provided by University of Sussex Library

Article

High-efficiency Co/CoxSy@S,N-codoped porous carbon electrocatalysts fabricated from controllably grown S, Nincluding Co-based MOFs for rechargeable zinc-air batteries Shengwen Liu, Xian Zhang, Guozhong Wang, Yunxia Zhang, and Haimin Zhang ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.7b11101 • Publication Date (Web): 12 Sep 2017 Downloaded from http://pubs.acs.org on September 12, 2017

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 free 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 accessible to all readers and 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.

ACS Applied Materials & Interfaces 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 33

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

ACS Applied Materials & Interfaces

High-efficiency

Co/CoxSy@S,N-codoped

porous

carbon electrocatalysts fabricated from controllably grown

S,

N-including

Co-based

MOFs

for

rechargeable zinc-air batteries Shengwen Liu,†,‡ Xian Zhang,†,§ ,‡ Guozhong Wang,† Yunxia Zhang,† and Haimin Zhang*,† †

Key Laboratory of Materials Physics, Centre for Environmental and Energy Nanomaterials,

Anhui Key Laboratory of Nanomaterials and Nanotechnology, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China §

University of Science and Technology of China, Hefei 230026, China

‡

These authors contributed equally

KEYWORDS. [Co(Tdc)(Bpy)]n; Solvent effect; S, N dual organic ligands; Bifunctional oxygen electrocatalysts; Zn-air battery

ACS Paragon Plus Environment

1


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 33

ABSTRACT. Developing bifunctional oxygen electrocatalysts with superior catalytic activities of oxygen reduction reaction (ORR) and oxygen revolution reaction (OER) is crucial to their practical energy storage and conversion applications. In this work, we report the fabrication of Co/CoxSy@S,N-codoped porous carbon structures with various morphologies, specific surface areas and pore structures, derived from controllably grown Co-based metal-organic frameworks with S- and N-containing organic ligands (thiophene-2,5-dicarboxylate, Tdc and 4,4ˊ-bipyridine, Bpy) utilizing solvent effect (e.g., water and methanol) under room temperature and hydrothermal conditions. The results demonstrate that Co/CoxSy@S,N-codoped carbon fibers fabricated at a pyrolytic temperature of 800 ºC (Co/CoxSy@SNCF-800) from Co-MOFs fibers fabricated in methanol under hydrothermal conditions as electrocatalysts exhibit superior bifunctional ORR and OER activities in alkaline media, endowing them as air cathodic catalysts in rechargeable zinc-air batteries with high power density and good durability.

1. INTRODUCTION Metal-organic frameworks (MOFs) with high crystalline nature and porous structure constructed by metal ions and organic linkers have exhibited great applicable potentials in separation/sorption, biomedicine, catalytic synthesis, optics and sensing, because of their unique features such as high specific surface area, orderly crystalline framework and porous structure.1-2 Currently, MOFs pyrolytically converted carbon-based materials are proven to be promising for clean and renewable energy applications with great potential for replacing expensive and scarce precious metal electrocatalysts (e.g., platinum-based and ruthenium/iridium-based catalysts) applied in water splitting, fuel cell and metal-air battery, arousing great research interest.3-7 It was found that the MOFs and their derived materials with controllable sizes, porous structure


2

Page 3 of 33

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


and morphologies play significant factors for their high application performance.8-9 For instance, Wang and co-workers synthesized N, P-codoped porous structure carbon nanofibers derived from 1D MOFs nanofibers, exhibiting better electrocatalytic performance for the oxygen reduction reaction (ORR), obviously superior to that of MOF crystals pyrolytically converted carbon materials.10 Cao et al. obtained 2D CoSNC nanocomposite from 2D MOFs nanosheets with better supercapacitive performance due to provided more active sites as compared to its bulk counterpart.11 Moreover, Shui et al. reported 3D nanofibrous MOFs network derived nanofibrous nonprecious metal catalysts, showing high ORR performance.12 Therefore, the development of new approaches for controlling MOFs precursors’ dimension, crystalline size, morphology and pore structure to synthesize high-efficiency electrocatalysts has attracted great research attentions. Although there are several methods have been developed, including surfactant-mediated methods,13 microemulsions,14 template-assisted methods,15 and modulating synthesis routes,16-17 most of endeavor in this field reported so far lacks rational and systematic investigation on controllable synthesis of MOFs and corresponding derivates for electrochemical energy application. Recently, “pillar-layer” method has been developed for constructing three-dimensional (3D) porous MOFs, which link specific two-dimension (2D) layer-like structures with one-dimension (1D) pillar structures.18-20 For example, multicarboxylates, grid, honeycomb, kagomenet and net are good candidates for MOF layer assemblies by rigid dipyridyl ligands, such as 4,4ˊ-bipyridine (bipy).18 This route should be an ideal and effective way for controlling the morphologies and sizes of MOFs, even selectively tune the MOFs nanocrystal growth direction along 1D, 2D, 3D through adjusting the different nucleated speeds of 2D networks-metal and 1D pillar-metal coordination, unfortunately, few reports involved in the literatures.


3


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 33

In most studies, N-containing organic molecules have been extensively used to synthesize Ndoped carbon-based bifunctional oxygen electrocatalysts toward ORR and OER (oxygen evolution reaction).3,

21

Porous carbon materials with N or/and S doping/co-doping recently

display excellent ORR performance, which are ascribed to the changes in both charge distribution and spin density stemmed from the interaction of carbon atoms and heteroatoms resulting in different surface electronegativity and electron spin.22-24 Recently, cobalt-based chalcogenides have been developed for ORR and OER applications, exhibiting good bifunctional catalytic activities.25 However, the OER activities of cobalt sulfides as well as heteroatomdoped/codoped carbon materials are still low and unsatisfied compared to other developed OER electrocatalysts. Therefore, the incorporation of transition metal oxides/sulfides into heteroatomdoped/codoped carbon may be an effective means to significantly improve the catalytic activity of electrocatalyst owing to a synergistic effect between different catalytic active species.26-28 Utilizing such approach mentioned above, cobalt sulfides incorporated into N, S-codoped carbon nanostructure could create more active sites, thus greatly improving the ORR and OER activities. Recently, some works have demonstrated that metal sulfides@S,N-codoped graphitic carbon materials can be obtained from N-including MOFs by the introduction of additional S-containing sources during pyrolysis.29-32 The fabricated S, N-codoped carbon materials with metal sulfides as electrocatalysts have demonstrated high activities of ORR and OER, however, the reported studies may include complex fabrication process and uncontrollable experiment repeatability using such additional S doping source approach. Therefore, utilization of S, N-containing organic ligands to obtain MOFs structures with fixed S/N ratio should be very feasible to fabricate high-efficiency S, N-codoped carbon-based electrocatalysts, which has been validated


4

Page 5 of 33

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


to be very effective for non-MOFs derived S, N-doped carbon materials.22,

33

However, the

related studies are few to date.34-35 Inspired by the “pillar-layer” strategy for fabricating 3D pillar-layer framework and synthetic methods for semiconductor nanocrystals, we designed a simple way for fabricating uniform MOFs nanocrystals with adjustable morphologies, crystalline sizes and growth directions using two types of organic ligands (i.e., with different chemical properties, such as hydrophilic, polarity, and solubility, et al.) and varying different reaction solvents. Herein, we have fabricated a porous pillared-layer structured [Co(Tdc)(Bpy)]n MOFs with doubly pillared layers utilizing thiophene-2,5-dicarboxylate―Tdc and 4,4ˊ-bipyridine―Bpy as organic linkers.36 For this pillarlayer structured [Co(Tdc)(Bpy)]n MOFs, Tdc ligands link Co2+ ions to construct a two-dimension (2D) rectangle-grid layer-like structure utilizing the carboxylate groups of organic linkers, and further these 2D layers can be assembled along one-dimensional (1D) direction by Bpy pillars to form three-dimensional (3D) porous MOFs (Scheme 1). It is found that different solvents such as water and methanol including reaction conditions (e.g., room temperature and hydrothermal treatment) can effectively regulate Co-based MOFs growth along 1D, 2D and 3D orientation, thus obtaining different structured S, N-containing Co-MOFs (Scheme 1). It is suggested that incorporating cobalt sulfides into N and S-codoped carbon nanostructure should greatly improve the catalytic activities of ORR and OER, therefore we utilize S, N-containing Co-MOFs as precursors, followed by further pyrolysis treatment, to realize one-step S, N doping with precisely controllable doping ratio and form coexistent Co/Co9S8/Co3S4 nanocrystals in graphitic carbon structure with controllable surface area and pore structure. Our experimental results demonstrate that Co/Co9S8/Co3S4@S,N-doped porous carbon fibers obtained at 800 ºC from [Co(Tdc)(Bpy)]n fibers fabricated in methanol at 120 ºC possess large surface area (212.1 m2 g-1)


5


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 33

and predominant mesoporous structure, showing superior bifunctional ORR and OER activities in alkaline media and high power density and good applicable stability for rechargeable zinc-air battery.

Scheme 1. Synthesis of Co-MOFs under different conditions

2. RESULTS AND DISCUSSION In our study, H2O (polarity of 10.2) and methanol (MeOH, polarity of 6.6) at the presence of NaOH as reaction solvents were used to controllably synthesize [Co(Tdc)(Bpy)]n MOFs with different structures under room temperature and hydrothermal conditions. The introduction of NaOH can effectively deprotonate Tdc, thus facilitating the connection between Co2+ and Tdc to form Co-MOFs basic structural units,37 while water/methanol including reaction conditions can effectively control the solubility of Tdc and Bpy in reaction system, thus resulting in different Co-MOFs structures. As expected, uniform sheet-like structures with the sizes of 1~3 µm and a thickness of ~200 nm were observed in H2O/NaOH at room temperature (Figure 1a and Figure S1a), indicating a preferential growth of 2D sheets ascribing to a high dissolution of Tdc in H2O/NaOH and a slight solubility of Bpy in such system at room temperature (Figure S2a-d), favourable for the linkage of Tdc and Co2+ to form 2D structures with less Bpy pillar layers. However, the dissolution of Bpy in H2O/NaOH can be effectively promoted under hydrothermal


6

Page 7 of 33

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


conditions of 120 ºC for 12 h, resulting in the formation of 3D bulk structures (Figure 1b and Figure S1b) owing to a concurrent growth of rectangle 2D Co-Tdc sheets and 1D Bpy doubly pillared layers.36 Interestingly, spindle-shape nanorods with ~80 nm in diameter and ~200 nm in length were obtained in MeOH/NaOH under room temperature (Figure 1c, Figure S1c), due to a low solubility of Tdc in MeOH/NaOH under room temperature unfavourable for the growth of 2D Co-Tdc sheets (Figure S2e, f). However, a high dissolution of Bpy in MeOH/NaOH can contribute the Co-MOFs growth along 1D direction (Figure S2g, h). Also, an enhanced solubility of Tdc in MeOH/NaOH under hydrothermal conditions facilitates the growth of 2D Co-Tdc sheets, while their growth rate is still lower than that of Bpy pillar layers along 1D orientation because of relatively low solubility of Tdc compared to Bpy in MeOH/NaOH, leading to the formation of uniform 1D fibers with 150~200 nm in diameter and 2~5 µm in length (Figure 1d and Figure S1d). Figure S3 displays the X-ray diffraction (XRD) patterns of the-prepared CoMOFs obtained under different conditions. All Co-MOFs samples show a crystal structure of orthorhombic space group (Pccn).36 The Co-MOFs 2D sheets obtained in H2O/NaOH at room temperature display good crystal nature with a preferentially grown (202) plane (line a), proving H2O/NaOH favourable for the linkage of Tdc and Co2+ to form 2D structures, while the spindleshape Co-MOFs 1D nanorods obtained from MeOH/NaOH at room temperature show weak diffraction peaks of (202), (020), (024), (133) and (233) planes (line c), indicating inferior crystallinity of the nanorods. After hydrothermal treatment, the obtained 3D bulks in H2O/NaOH (line b) and 1D fibers in MeOH/NaOH (line d) all exhibit good crystal nature with several new diffraction peaks, indicating a continued growth of 2D sheets and 1D nanorods to form 3D bulks and 1D fibers with preferentially grown (302) crystal plane. The XRD analysis indicates that the reaction conditions including reaction solvent and temperature have crucial effect on the as-


7


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 33

prepared Co-MOFs structures, possibly leading to the Co-MOFs pyrolytically converted carbon materials with various specific surface areas, pore structures and S, N doping ratios, thus contributing significantly different electrocatalytic activities as electrocatalysts.

Figure 1. SEM images of (a) 2D sheets in H2O/NaOH and (c) 1D nanorods in MeOH/NaOH at room temperature; (b) 3D bulks in H2O/NaOH and (d) 1D fibers in MeOH/NaOH under hydrothermal conditions. Many studies have demonstrated that porous structures of MOFs can be well inherited after pyrolysis, leading to the carbon structures from MOFs precursors with high specific surface area and porous structure, thus delivering high electrocatalytic performance as electrocatalysts.38-40 In this work, the presence of doubly pillared layer structures aroused from Bpy ligands results in Co-MOFs with a high thermal stability.36 This means that the formed Co-MOFs with more doubly pillared layers may be beneficial for the structure maintenance of pyrolytic carbon products. Figure S4 shows the SEM images of Co-MOFs derived carbon products. As shown, the carbon products derived from 2D sheets and 1D nanorods respectively obtained in H2O/NaOH


8

Page 9 of 33

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


and MeOH/NaOH at room temperature exhibit seriously damaged structures at a pyrolysis temperature of 800 ºC owing to their corresponding MOFs structures with less doubly pillared layers (Figure S4a, c, denoted as Co/CoxSy@SNCS-800 and Co/CoxSy@SNCN-800). However, the carbon products derived from their hydrothermally fabricated Co-MOFs with more pillared layers show relatively intact porous 3D bulk (Figure S4b, denoted as Co/CoxSy@SNCB-800) and 1D fiber (Figure S4d, denoted as Co/CoxSy@SNCF-800) structures. Figure 2 gives the XRD results of all pyrolytically converted carbon products achieved at 800 ºC. The diffraction peaks at 15.4, 29.8, 31.1, 39.5, 44.8, 47.6 and 51.9º for all samples can be indexed to the (111), (311), (222), (331), (422), (511) and (440) planes of Co9S8 (JCPDS card No. 86-2273),41 indicating the formation of Co9S8 in carbon products. Also, it is found that apart from Co9S8 phase, the new diffraction peaks at 31.8, 47.6 and 75.4º can be ascribed to the planes (311), (422), (642) of Co3S4 (JCPDS No. 02-0825) in samples,29 while the peak of 45.8º can be indexed to the (111) crystalline plane for the cubic metallic Co (JCPDS Card No. 88-2325), respectively.42 Interestingly, the strong diffraction peak intensities of Co3S4 and Co in Co/CoxSy@SNCF-800 and

Co/CoxSy@SNCN-800

are significantly decreased

in

Co/CoxSy@SNCS-800

and

Co/CoxSy@SNCB-800, indicating the Co-MOFs precursor synthesized from methanol as solvent tending to form Co9S8, comparatively, not only Co9S8, the grown Co-MOFs in water were also favorable for forming Co3S4 and metal Co during pyrolysis process. The cobalt sulfides with multi-phases and different valence states of cobalt formed in Co/CoxSy@SNCF-800 and Co/CoxSy@SNCN-800 may be favourable for creating catalytic active sites and synergy effect for high performance electrocatalysis.29


9


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 33

Figure 2. XRD patterns of Co-MOFs derived carbon products at 800 ºC. Line a, Co/CoxSy@SNCF-800; line b, Co/CoxSy@SNCN-800; line c, Co/CoxSy@SNCS-800; line d, Co/CoxSy@SNCB-800. Figure 3a, b shows the electronic microscopy (SEM and TEM) characterizations of Co/CoxSy@SNCF-800. Obviously, the obtained carbon fibers exhibit the diameters of 100~150 nm, less than Co-MOFs fibers with diameters of 150~200 nm owing to a pyrolysis shrinkage (Figures S1d, S4d and Figure 3a). Also, uniformly encapsulated Co/CoxSy nanoparticles into carbon structure with the sizes of 50~100 nm can be clearly observed (Figure 3b and Figure S5). The HRTEM images (Figure 3c, d) indicate that the formed CoxSy nanoparticles are composed of primary Co9S8 crystals with a lattice spacing of 0.573 nm assigned to the (111) crystalline plane, and Co3S4 nanocrystals with the lattice spacings of 0.281 nm and 0.198 nm of metal Co nanocrystal, further confirming a coexistence of Co/Co9S8/Co3S4 in carbon sample. This is in agreement with the XRD analysis. Noticeably, the interfaces between close-stacking Co9S8 and Co3S4, Co are visible, which would benefit the synergy of surface catalytic activity.43 The corresponding SAED patterns (Figure 3e) can be ascribed to the crystalline planes of Co9S8, Co3S4 and metallic Co, suggesting their good crystalline nature. Further, the high-magnification


10

Page 11 of 33

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


TEM image displays the fabricated carbon fiber possesses porous structure with the pore sizes of 5~20 nm (Figure 3f, g). Such porous structure is conductive to electrocatalysis-relevant mass transport, thus fully utilizing pore inner catalytic active sites for high efficiency electrocatalysis. The elemental mapping analysis (Figure 3h) reveals that C, N and S are uniformly dispersed over the entire carbon fiber, moreover, the distribution of S element is very apparent at CoxSy particles. The above results confirm the presence of Co9S8/Co3S4 and S, N co-doping in carbon, which are electrocatalysis active species to create catalytic active sites for high performance electrocatalysis.27, 29


11


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 33

Figure 3. (a) SEM image of Co/CoxSy@SNCF-800 fiber; (b) TEM image of an individual Co/CoxSy@SNCF-800 fiber; (c), (d) HRTEM images of Co/CoxSy particles; (e) SAED patterns of Co/CoxSy particles; (f), (g) TEM image of porous carbon fibers; (h) Elemental mapping images of C, S, N and Co in 1D carbon fibers obtained from f. Figure S6 shows the N2 adsorption/desorption isotherms and corresponding pore size distribution curves of the pyrolytic carbon products. As shown in Table S1, Co/CoxSy@SNCF800 exhibits the largest specific surface area of 212.1 m2 g-1 among all samples. The pore size distribution curves indicate that all carbon samples show bimodal microporous and mesoporous structures, moreover, mesoporous structure is predominant for Co/CoxSy@SNCF-800. The microporous and mesoporous structure not only improves specific surface area of carbon material beneficial for the utilization of catalytic active sites, but also enhances the mass transport, therefore improving the electrocatalysts’ performance.22, 44-45 The surface chemical composition of Co-MOFs derived carbon products were examined by XPS technique. In this work, Co/CoxSy@SNCF-700 and Co/CoxSy@SNCF-900 were also analyzed by XPS to obtain a meaningful comparison. The surface survey spectra (Figure S7) indicate that all samples show the presence of carbon (C), nitrogen (N), sulfur (S), oxygen (O) and cobalt (Co) elements. As shown in Table S2, the atomic ratio of S/N is 2.2 for Co/CoxSy@SNCS-800, while the atomic ratios are decreased for Co/CoxSy@SNCB-800 (S/N=1.7), Co/CoxSy@SNCN-800 (S/N=1.6) and Co/CoxSy@SNCF-800 (S/N=1.9). A higher S/N atomic ratio of Co/CoxSy@SNCS-800 suggests a preferential growth of Co-Tdc sheets with less N-containing Bpy pillared layers, whereas a decrease in S/N ratio indicates the increase of N-containing Bpy pillared layers in Co-MOFs structures. This is consistent with the SEM analysis (Figure 1). The high-resolution N 1s XPS spectra show that all carbon products


12

Page 13 of 33

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


investigated contain pyridinic N, pyrrolic N, graphitic N and oxidized N (Figure S8 and Table S3).25, 46 It is found that the pyridinic N and graphitic N are predominant for Co/CoxSy@SNCF800 and Co/CoxSy@SNCN-800, favourable for improving electrocatalysis activities of electrocatalysts, while oxidized N is dominant for Co/CoxSy@SNCS-800 and Co/CoxSy@SNCB800. Moreover, an increase of pyrolysis temperature is in favor of the conversion of N doping from pyridinic N to graphitic N (taking Co/CoxSy@SNCF-800 as an example). Recent study published in Science has revealed that pyridinic N takes a decisive role in creating ORR active sites compared to graphitic N by a precisely controlled N doping means.47 This means that Co/CoxSy@SNCF-800 with relatively predominant pyridinic N combining with advantageous structure properties may be helpful for improving the ORR catalytic activities. The high resolution S 2p spectra (Figure S9) of all carbon samples indicate the presence of Co-S and C-SC, further ascertaining the formation of Co9S8/Co3S4 and S doping in carbon.25, 27 The highresolution C 1s spectra (Figure S10) further verify S, N co-doping in carbon structure. The highresolution Co 2p XPS spectra of all carbon products (Figure S11) show the peaks at 781.61 and 784.88 eV assigned to the 2p3/2 of Co2+ and Co3+, and the peaks at the binding energies of 779.36 and 784.88 eV attributed to the 2p1/2 of Co2+ and Co3+, and two satellites peaks (abbreviated as “Sat.”), respectively,48 implying Co9S8/Co3S4 in carbon structure. In this study, we measured the electrocatalytic ORR and OER performance using Co-based MOFs derived carbon materials as electrocatalysts. For comparison, platinum/carbon (Pt/C) and RuO2 electrocatalysts were also measured with the identical experimental conditions. For ORR measurements, the LSV curves (Figure 4a) obtained at 1600 rpm in O2 saturated 0.1 M KOH display that Co/CoxSy@SNCS-800, Co/CoxSy@SNCN-800 and Co/CoxSy@SNCF-800 exhibit close onset potential values of 0.85, 0.83 and 0.83 V, and half-wave potential values of 0.76,


13


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 33

0.75 and 0.74 V, superior to those of Co/CoxSy@SNCB-800 (0.79 V for onset potential and 0.69 V for half-wave potential) possibly due to its low specific surface area. The onset potentials of Co/CoxSy@SNCS-800, Co/CoxSy@SNCN-800 and Co/CoxSy@SNCF-800 are slightly negative shift compared to that of Pt/C (0.93 V for onset potential and 0.79 V for half-wave potential), but their close half-wave potentials indicate good ORR activities of these electrocatalysts. Importantly, the limiting current densities of Co/CoxSy@SNCF-800 are obviously higher than other carbon-based and Pt/C catalysts, indicating its high ORR catalytic performance possibly due to a synergistic effect of high specific surface area favourable for the exposure of catalytic active species, Co/CoxSy and suitable S, N co-doping in carbon structure producing more active sites, and dominant mesoporous structure to improve mass transport.45,

49

The pyrolysis

temperature influencing experiments (Figure S12a) demonstrate that Co/CoxSy@SNCF-800 exhibits high ORR performance in comparison with the catalysts obtained at 700 ºC and 900 ºC. It is believed that suitable Co/CoxSy and S, N doping combining with structural benefits in CoxSy@SNCF-800 afford its high ORR activity. Figure 4b displays the LSV plots of Co/CoxSy@SNCF-800 in O2 saturated 0.1 M KOH under various rotation rates. The KouteckyLevich (K-L) curves (Figure S13a) exhibit linear relationships at 0.2~0.6 V and the average transferred electron number ( n ) was calculated to be 3.97 (Figure S13b), very close to that of Pt/C catalyst (Figure S14), indicating a four electron ORR process.50 With the same experimental conditions, the

n

values are 3.88, 3.18 and 3.90 for Co/CoxSy@SNCS-800, Co/CoxSy@SNCB-

800 and Co/CoxSy@SNCN-800, respectively (Figure S15-17), further indicating high ORR activity of Co/CoxSy@SNCF-800.


14

Page 15 of 33

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


Figure

4.

(a)

ORR

performance

of

Co/CoxSy@SNCS-800,

Co/CoxSy@SNCB-800,

Co/CoxSy@SNCN-800, Co/CoxSy@SNCF-800, and Pt/C; (b) LSV plots of Co/CoxSy@SNCF800 at various rotation rates; (c) OER performance of Co/CoxSy@SNCS-800, Co/CoxSy@SNCB800, Co/CoxSy@SNCN-800, Co/CoxSy@SNCF-800, and RuO2; (d) Tafel plots of all investigated electrocatalysts with a scan rate of 10 mV s-1 in O2 saturated 0.1 M KOH under 1600 rpm. The OER activities of Co-MOFs derived carbon electrocatalysts were also evaluated in O2 saturated 0.1 M KOH with a rotating speed of 1600 rpm. As displayed in Figure 4c, the potential values at current density of 10 mA cm-2 are 1.593, 1.629, 1.552, 1.542 and 1.536 V for Co/CoxSy@SNCS-800, Co/CoxSy@SNCB-800, Co/CoxSy@SNCN-800, Co/CoxSy@SNCF-800 and RuO2 respectively, affording the overpotentials of 0.364, 0.40, 0.323, 0.313 and 0.307 V (Figure S18). Apparently, the overpotential at current density of 10 mA cm-2 of Co/CoxSy@SNCF-800 is very approximate to that of RuO2 catalyst, indicating its high activity toward OER. Also, the pyrolysis temperature of 800 ºC is found to be suitable for obtaining high active OER electrocatalyst compared to the samples obtained at 700 ºC and 900 ºC (Figure S12b).


15


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 33

The Tafel polarization characterization further verifies high OER performance of Co/CoxSy@SNCF-800, as shown in Figure 4d. The obtained Tafel slope values were calculated to be 100, 106, 88, 68 and 59 mV dec-1 for Co/CoxSy@SNCS-800, Co/CoxSy@SNCB-800, Co/CoxSy@SNCN-800,

Co/CoxSy@SNCF-800

and

RuO2,

respectively.

Apparently,

Co/CoxSy@SNCF-800 exhibits an approximate Tafel slope with RuO2 catalyst, indicating a superior OER activity of Co/CoxSy@SNCF-800. Remarkably, the Co/CoxSy@SNCF-800 and Co/CoxSy@SNCN-800 where Co/CoxSy composed of Co, Co3S4, Co9S8 exhibit superior OER performance than the Co/CoxSy@SNCB-800 and Co/CoxSy@SNCS-800 with dominate composition of Co9S8, this is consistent with the diverse ORR performances of Co/CoxSy@SNCX-T, confirmed the multi-phases of Co/CoxSy in the Co/CoxSy@SNCX-T is favorable for higher OER and ORR performance. To understand the important role of Co/CoxSy and N, S co-doping in Co/CoxSy@SNCF-800, pure N, S-codoped porous carbon nanofiber (SNCF-800) was fabricated in this work for evaluating their ORR and OER activities (Figure S19 and Figure S20). Interestingly, we found that SNCF-800 also exhibits bifunctional OER and ORR activities. However, the SNCF-800 shows higher OER overpotential at 10 mA cm-2, and slightly decreased ORR activity compared to Co/CoxSy@SNCF-800, indicating SNCF-800 possesses excellent ORR activity and worse OER performance. The above results illustrate that Co/CoxSy can provide more active sites to improve the ORR and OER performances, especially for improving the OER performance. Further, as described above, it was found that Co/CoxSy@SNCF-800 and Co/CoxSy@SNCN-800 with Co/CoxSy composed of Co, Co3S4, Co9S8 possesses higher ORR and OER performance than the Co/CoxSy@SNCB-800 and Co/CoxSy@SNCS-800 where CoxSy mainly composed of Co9S8. Moreover, it is reported that besides of Co9S8, Co3S4 and metallic Co also possesses high OER


16

Page 17 of 33

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


and ORR performance.51-52 The above results suggest the synergetic effect between the active species of Co, Co9S8, and Co3S4 for improving oxygen reaction performance of electrocatalyst. Therefore, high ORR and OER activities of Co/CoxSy@SNCF-800 indicates that the synergistic interactions between Co/CoxSy and N, S co-doping, as well as the synergistic interactions between Co, Co3S4, Co9S8 of Co/CoxSy, play critical role for improving catalyst’s ORR and OER activities.41 Additionally, the difference in ORR and OER activities of Co/CoxSy@SNCX-T catalysts could be due to their different specific surface area, pore structure, graphitization degree and S, N-codoped amount.34

Figure 5. (a), (b) Power density curves and open-circuit voltage measurements of zinc-air batteries with different catalysts; (c) Charging-discharging polarization plots of rechargeable zinc-air batteries with different catalysts; (d) Stability measurement of Co/CoxSy@SNCF-800 based zinc-air battery.


17


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 33

An electrocatalyst with the bifunctionality of ORR and OER is vital to a practical rechargeable metal-air battery application.53-55 In this study, the Co/CoxSy@SNCF-800 as air cathodic catalyst was evaluated for zinc-air battery. Figure 5a displays the performance of zincair batteries made of Co/CoxSy@SNCF-800 and Pt/C+RuO2. As shown, the zinc-air battery made of Co/CoxSy@SNCF-800 with a high current density of 138 mA cm-2 at 1.0 V can be observed in the discharge process, approximate to that of Pt/C-RuO2 constructed zinc-air battery (158 mA cm-2 at 1.0 V). The maximum power density can reach 230 mW cm-2 at 0.65 V with a current density of 358 mA cm-2 for Co/CoxSy@SNCF-800 assembled zinc-air battery, singnificantly higher than that (215 mW cm-2 reached at 0.72 V) of Pt/C-RuO2 based zinc-air battery at 296 mA cm-2 and other Co-MOFs derived air cathode materials (Figure S21a). Owing to the superior bifunctionality of ORR and OER of Co/CoxSy@SNCF-800, a rechargeable zinc-air was also built to evaluate its performance as air cathode material. The open-circuit voltage was measured to be 1.37 V for the rechargeable zinc-air battery made from Co/CoxSy@SNCF-800 (Figure 5b), identical with that obtained from Pt/C-RuO2 assembled zinc-air battery. During the chargingdischarging process (Figure 5c and Figure S21b), Co/CoxSy@SNCF-800 based rechargeable zinc-air battery shows the current densities similar with the rechargeable zinc-air battery based on Pt/C-RuO2 catalyst, indicating the superior charging-discharging performance. The durability test demonstrates that the initial charging and discharging potentials of Co/CoxSy@SNCF-800 based rechargeable zinc-air battery are 1.96 V and 1.26 V, respectively, while the charging and discharging potentials after 468 cycles are 1.98 V and 1.23 V (Figure 5d), indicating high recycling stability possibly ascribed to Co/CoxSy nanoparticles encapsulated into graphitic carbon structure to improve catalyst’s stability.

3. CONCLUSION


18

Page 19 of 33

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


In summary, we have developed high-efficiency Co/CoxSy@S,N-codoped porous carbon fiber electrocatalyst with the bifunctionality of ORR and OER derived from controllably grown [Co(Tdc)(Bpy)]n MOFs fibers utilizing solvent effect. The obtained Co/CoxSy@SNCF-800 as air cathodic catalyst exhibits high power density and good durability in rechargeable zinc-air battery due to its superior bifunctional activities toward ORR and OER. The results obtained in this study are very helpful to fabricate high-efficiency electrocatalysts with multifunctional catalytic activities by regulating MOFs precursor structures utilizing solvent effect for applications in renewable energy technologies.

4. EXPERIMENTAL SECTION 4.1 Materials Tdc (2, 5-Thiophenedicarboxylic acid, AR 98%, Aladdin), 4,4ˊ-Bpy (4,4ˊ-Bipyridine, AR 98%, Aladdin) and KOH (AR 98%, Aladdin) were ordered from Aladdin Reagent Company, and Nafion electrolyte (wt.5%) used in this work was from DuPont Company. H2SO4, KMO4, NaOH, NaNO3, Zn(NO3)2·6H2O, HCL (wt.36% ~ 38%) and CH3OH (≥99.7%) were purchased from Sinopharm Chemical Reagent Co., Ltd. Commercial platinum/carbon (Pt/C) catalyst was ordered from Alfa Aesar, and commercial RuO2 (99.9%) catalyst was from Sigma-Aldrich. All obtained chemicals were used as purchased without any further purification except for special notification. 4.2 Preparation of materials Preparation of [Co(Tdc)(Bpy)]n. For the fabrication of 2D [Co(Tdc)(Bpy)]n sheets, CoCl2·6H2O (228 mg ) was firstly dissolved in deionized water (10 mL), and subsequently the fabricated Co2+ solution (10 mL) was added to a 20 mL of mixture of Tdc (280 mg), NaOH (132 mg) and 4,4ˊ ˊ-Bpy (296 mg) under room temperature for stirring for 5 min. On one hand, the obtained product was collected by filtration and then dried at 60 °C for overnight, 2D


19


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 33

[Co(Tdc)(Bpy)]n sheets were obtained. On the other hand, the above mixture without filtration process was directly moved to a Teflon vessel (80 mL) in steel structure autoclave and maintained at 120 °C for 12 h, the resulting products were collected by filtration, followed by dried at 60 °C for overnight, 3D bulk structure [Co(Tdc)(Bpy)]n was obtained. 1D [Co(Tdc)(Bpy)]n spindle-shape nanorods and fibers were also fabricated utilizing the same synthetic process aforementioned except for methanol replacing H2O as solvent. The as-prepared 1D [Co(Tdc)(Bpy)]n spindle-shape nanorods/fibers were obtained under room temperature and hydrothermal conditions, respectively. Preparation of Co/CoxSy@SNCX-T electrocatalyst materials. As reaction precursors, the synthesized [Co(Tdc)(Bpy)]n MOFs were pyrolytically treated with various temperatures for 2 h in N2 to obtain CoxSy@SNCX-T materials (X represents the abbreviation of [Co(Tdc)(Bpy)]n crystals with different morphologies including 2D sheets (S), 3D bulks (B), 1D nanorods (N) and 1D fibers (F); T represents pyrolysis temperature of 700, 800 and 900 °C. For example, the CoMOFs derived carbon products obtained at 800 °C were denoted as Co/CoxSy@SNCS-800, Co/CoxSy@SNCB-800, Co/CoxSy@SNCN-800 and Co/CoxSy@SNCF-800. Preparation of SNCF-800 electrocatalyst materials. The Co/CoxSy@SNCF-800 was further treated in hydrochloride acid (HCl) solution (6.0 M) for 12 h, followed by washing through deionized water and repeated this process for four times, the SNCF-800 can be obtained. 4.3 Characterizations The crystalline phase information of samples was obtained through powder X-ray diffraction (XRD) technique (Philips X-Pert Pro X-ray diffractometer). The surface morphologies of samples were recorded using field emission scanning electron microscopy (FESEM) (Quanta 200 FEG) with an operation voltage of 10.0 kV. The detailed structure and elemental mapping


20

Page 21 of 33

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


characterizations of samples were performed by transmission electron microscopy (TEM) technique (JEOL2010) with an acceleration voltage of 200 kV. The surface area and porosity analyzer (Tristar 3020M) was used to measure the specific surface area and porosity of samples. The chemical state and elemental composition of samples were analyzed using X-ray photoelectron spectroscopy (XPS) technique (ESCALAB 250, Thermo, America) with Al Kα1,2 monochromatized radiation at 1486.6 eV. 4.4 Electrochemical experiments In this work, all the electrochemical experiments of electrocatalysts were carried out in a threeelectrode cell with catalyst coated glassy carbon (GC) working electrode, Ag/AgCl reference and platinum wire counter electrode, using a CHI 760D electrochemical workstation (CH Instruments, Inc., Shanghai, China) with a rotation disk electrode (RDE) system (Pine Instruments Co. Ltd. USA). The potentials used in this study are versus the reversible hydrogen electrode (RHE) through a potential (vs. Ag/AgCl, 4.0 M KCl) conversion as follows:

ERHE = EAg/AgCl + 0.059pH + E° Ag/AgCl where ERHE represents the potential (vs. RHE), EoAg/AgCl=0.197 V at 25°C, and EAg/AgCl represents the potential (vs. Ag/AgCl) experimentally measured. The working electrode was a glassy carbon electrode with a diameter of 5.0 mm, and 0.1 M KOH as electrolyte was used during measurements. The well-dispersed catalyst ink was prepared by ultrasonically dispersing 4.0 mg catalyst into a mixture (1000 µL) composed of Nafion (5%), ethanol and deionized water with a volume ratio of 1:1:1. Then, the working electrode with catalyst was prepared by casting 20 µL of catalyst ink on glassy carbon (GC) electrode surface, followed by drying at room temperature for electrochemical measurement.


21


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 33

ORR performance measurements of catalysts: The ORR activities of catalysts were first evaluated by cyclic voltammetry (CV) measurements within the potential range of 0.2~1.0 V (vs. RHE) in N2-/O2-saturated 0.1 M KOH electrolyte at a CV scan rate of 50 mV s-1. RDE measurements were performed in O2-saturated 0.1 M KOH electrolyte at a sweep rate of 10 mV s-1 with various rotation speeds of 400, 625, 900, 1225 and 1600 rpm. For comparison, the commercial 20 wt.% platinum on carbon black (Pt/C) was also measured under the identical experimental conditions. At various potentials, the transferred electron number (n) per oxygen molecule during ORR was obtained by the following Koutecky-Levich (K-L) equation: 1 1 1 1 1 = + = + 1/2 J J L J K Bω JK

B = 0.2nFC0 ( D0 )2 / 3 v −1 / 6 J K = nFkC0

where J represents the current density experimentally measured, JL and JK represent the diffusion current density and limiting current densities, ω expresses the rotating rate, ݊ is the transferred electron number per oxygen molecule, F represents Faraday constant (96485 C mol-1), C0 represents the concentration of O2 in 0.1 M KOH (1.26×10-6 mol cm-3), D0 is the O2 diffusion coefficient in 0.1 M KOH (1.9×10-5 cm2 s-1), and ν represents the solution kinetic viscosity (0.01 cm2 s-1). OER performance measurements of catalysts: OER measurements were carried out in O2saturated 0.1 M KOH solution. The linear sweep voltammetry (LSV) technique was applied to obtain the polarization curves with iR compensation of catalysts within the potential range of 1.0~1.7 V (vs. RHE) at a scanning rate of 10 mV s–1 under 1600 rpm.


22

Page 23 of 33

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


Zinc-air battery evaluation: A home-made zinc-air battery was measured on an electrochemical workstation (Zahner-Zennium) under room temperature. Briefly, this homemade zinc-air battery is composed of pre-polished zinc foil as anodic material and electrocatalyst coated on Teflon-coated carbon paper (2.0 mg cm-2 for catalyst loading) as air cathode. 6.0 M KOH as well as 0.2 M Zn(Ac)2 was used as electrolyte of home-made zinc-air battery. ASSOCIATED CONTENT

Supporting Information. Details of Co-MOFs characterization, including SEM, TEM, XRD, XPS and BET measurements, LSV curves and corresponding K–L curves of the Co/CoxSy@SNCX-T and Pt/C electrocatalysts, performance measurements of zinc-air batteries. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION

Corresponding Author *Email: [email protected]

Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡ These authors contributed equally.

Notes The authors declare no competing financial interest ACKNOWLEDGMENT


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

Page 24 of 33

We thank the financial support from the National Natural Science Foundation of China (Grant No. 51672277), the CAS Pioneer Hundred Talents Program, and the CAS/SAFEA International Partnership Program for Creative Research Teams of Chinese Academy of Sciences, China. REFERENCES (1) Slater, A. G.; Cooper, A. I., Porous Materials. Function-Led Design of New Porous Materials. Science 2015, 348, aaa8075. (2) Cui, Y.; Li, B.; He, H.; Zhou, W.; Chen, B.; Qian, G., Metal–Organic Frameworks as Platforms for Functional Materials. Accounts. Chem. Res. 2016, 49, 483-493. (3) Ma, T. Y.; Dai, S.; Jaroniec, M.; Qiao, S. Z., Metal-Organic Framework Derived Hybrid Co3O4-Carbon Porous Nanowire Arrays as Reversible Oxygen Evolution Electrodes. J. Am. Chem. Soc. 2014, 136, 13925-13931. (4) Liu, S.; Zhang, H.; Zhao, Q.; Zhang, X.; Liu, R.; Ge, X.; Wang, G.; Zhao, H.; Cai, W., MetalOrganic Framework Derived Nitrogen-Doped Porous Carbon@Graphene Sandwich-Like Structured Composites as Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions. Carbon 2016, 106, 74-83. (5) You, B.; Jiang, N.; Sheng, M.; Gul, S.; Yano, J.; Sun, Y., High-Performance Overall Water Splitting Electrocatalysts Derived from Cobalt-Based Metal–Organic Frameworks. Chem. Mater.

2015, 27, 7636-7642. (6) Liu, M.; Li, J., Cobalt Phosphide Hollow Polyhedron as Efficient Bifunctional Electrocatalysts for the Evolution Reaction of Hydrogen and Oxygen. ACS Appl. Mater. Interfaces 2016, 8, 2158-2165.


24

Page 25 of 33

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


(7) Wang, Z.; Xiao, S.; Zhu, Z.; Long, X.; Zheng, X.; Lu, X.; Yang, S., Cobalt-Embedded Nitrogen Doped Carbon Nanotubes: A Bifunctional Catalyst for Oxygen Electrode Reactions in a Wide pH Range. ACS Appl. Mater. Interfaces 2015, 7, 4048-4055. (8) Xia, W.; Mahmood, A.; Zou, R.; Xu, Q., Metal–Organic Frameworks and Their Derived Nanostructures for Electrochemical Energy Storage and Conversion. Energy Environ. Sci. 2015, 8, 1837-1866. (9) Mahmood, A.; Guo, W.; Tabassum, H.; Zou, R., Metal ‐ Organic Framework ‐ Based Nanomaterials for Electrocatalysis. Adv. Energy. Mater. 2016, 1600423. (10) Zhang, W.; Wu, Z. Y.; Jiang, H. L.; Yu, S. H., Nanowire-Directed Templating Synthesis of Metal-Organic Framework Nanofibers and Their Derived Porous Doped Carbon Nanofibers for Enhanced Electrocatalysis. J. Am. Chem. Soc. 2014, 136, 14385-14388. (11) Cao, F.; Zhao, M.; Yu, Y.; Chen, B.; Huang, Y.; Yang, J.; Cao, X.; Lu, Q.; Zhang, X.; Zhang, Z.; Tan, C.; Zhang, H., Synthesis of Two-Dimensional CoS1.097/Nitrogen-Doped Carbon Nanocomposites Using Metal–Organic Framework Nanosheets as Precursors for Supercapacitor Application. J. Am. Chem. Soc. 2016, 138, 6924-6927. (12) Shui, J.; Chen, C.; Grabstanowicz, L.; Zhao, D.; Liu, D. J., Highly Efficient Nonprecious Metal Catalyst Prepared with Metal-Organic Framework in a Continuous Carbon Nanofibrous Network. Proc. Natl. Acad. Sc.i Usa 2015, 112, 10629-10634. (13) Pan, Y.; Heryadi, D.; Zhou, F.; Zhao, L.; Lestari, G.; Su, H.; Lai, Z., Tuning the Crystal Morphology and Size of Zeolitic Imidazolate Framework-8 in Aqueous Solution by Surfactants. CrystEngComm 2011, 13, 6937-6940. (14) Carne, A.; Carbonell, C.; Imaz, I.; Maspoch, D., Nanoscale Metal-Organic Materials. Chem. Soc. Rev. 2011, 40, 291-305.


25


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 26 of 33

(15) Huang, X.; Zheng, B.; Liu, Z.; Tan, C.; Liu, J.; Chen, B.; Li, H.; Chen, J.; Zhang, X.; Fan, Z.; Zhang, W.; Guo, Z.; Huo, F.; Yang, Y.; Xie, L. H.; Huang, W.; Zhang, H., Coating TwoDimensional Nanomaterials with Metal-Organic Frameworks. ACS Nano 2014, 8, 8695-8701. (16) Pham, M. H.; Vuong, G. T.; Fontaine, F. G.; Do, T. O., Rational Synthesis of Metal-Organic Framework Nanocubes and Nanosheets Using Selective Modulators and Their MorphologyDependent Gas-Sorption Properties. Cryst. Growth Des. 2012, 12, 3091-3095. (17) Tsuruoka, T.; Furukawa, S.; Takashima, Y.; Yoshida, K.; Isoda, S.; Kitagawa, S., Nanoporous Nanorods Fabricated by Coordination Modulation and Oriented Attachment Growth. Angew. Chem. Int. Ed. 2009, 48, 4739-4743. (18) Han, L.; Xu, L.-P.; Qin, L.; Zhao, W.-N.; Yan, X.-Z.; Yu, L., Syntheses, Crystal Structures, and Physical Properties of Two Noninterpenetrated Pillar-Layered Metal–Organic Frameworks Based On N,N′-Di(4-Pyridyl)-1,4,5,8-Naphthalenetetracarboxydiimide Pillar. Cryst. Growth Des. 2013, 13, 4260-4267. (19) Meng, X.; Zhong, R. L.; Song, X. Z.; Song, S. Y.; Hao, Z. M.; Zhu, M.; Zhao, S. N.; Zhang, H. J., A Stable, Pillar-Layer Metal-Organic Framework Containing Uncoordinated Carboxyl Groups for Separation of Transition Metal Ions. Chem. Commun. 2014, 50, 6406-6408. (20) Sen, S.; Neogi, S.; Aijaz, A.; Xu, Q.; Bharadwaj, P. K., Construction of Non-Interpenetrated Charged Metal-Organic Frameworks with Doubly Pillared Layers: Pore Modification and Selective Gas Adsorption. Inorg. Chem. 2014, 53, 7591-7598. (21) You, B.; Jiang, N.; Sheng, M.; Drisdell, W. S.; Yano, J.; Sun, Y., Bimetal–Organic Framework Self-Adjusted Synthesis of Support-Free Nonprecious Electrocatalysts for Efficient Oxygen Reduction. ACS Catal. 2015, 5, 7068-7076.


26

Page 27 of 33

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


(22) Li, Y.; Zhang, H.; Wang, Y.; Liu, P.; Yang, H.; Yao, X.; Wang, D.; Tang, Z.; Zhao, H., A Self-Sponsored Doping Approach for Controllable Synthesis of S and N Co-Doped TrimodalPorous Structured Graphitic Carbon Electrocatalysts. Energy Environ. Sci. 2014, 7, 3720-3726. (23) Paraknowitsch, J. P.; Thomas, A., Doping Carbons Beyond Nitrogen: An Overview of Advanced Heteroatom Doped Carbons with Boron, Sulphur and Phosphorus for Energy Applications. Energy Environ. Sci. 2013, 6, 2839-2855. (24) Zhu, Q.; Lin, L.; Jiang, Y.-F.; Xie, X.; Yuan, C.-Z.; Xu, A.-W., Carbon Nanotube/S-N-C Nanohybrids as High Performance Bifunctional Electrocatalysts for Both Oxygen Reduction and Evolution Reactions. New J. Chem. 2015, 39, 6289-6296. (25) Dou, S.; Tao, L.; Huo, J.; Wang, S.; Dai, L., Etched and Doped Co9S8/Graphene Hybrid for Oxygen Electrocatalysis. Energy Environ. Sci. 2016, 9, 1320-1326. (26) Peng, S.; Li, L.; Han, X.; Sun, W.; Srinivasan, M.; Mhaisalkar, S. G.; Cheng, F.; Yan, Q.; Chen,

J.;

Ramakrishna,

S.,

Cobalt

Sulfide

Nanosheet/Graphene/Carbon

Nanotube

Nanocomposites as Flexible Electrodes for Hydrogen Evolution. Angew. Chem. Int. Ed. 2014, 53, 12594-12599. (27) Ganesan, P.; Prabu, M.; Sanetuntikul, J.; Shanmugam, S., Cobalt Sulfide Nanoparticles Grown on Nitrogen and Sulfur Codoped Graphene Oxide: An Efficient Electrocatalyst for Oxygen Reduction and Evolution Reactions. ACS Catal. 2015, 5, 3625-3637. (28) Liang, Y.; Li, Y.; Wang, H.; Zhou, J.; Wang, J.; Regier, T.; Dai, H., Co3O4 Nanocrystals on Graphene as a Synergistic Catalyst for Oxygen Reduction Reaction. Nat. Mater. 2011, 10, 780786.


27


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 28 of 33

(29) Chen, B.; Li, R.; Ma, G.; Gou, X.; Zhu, Y.; Xia, Y., Cobalt Sulfide/N,S Codoped Porous Carbon Core-Shell Nanocomposites as Superior Bifunctional Electrocatalysts for Oxygen Reduction and Evolution Reactions. Nanoscale 2015, 7, 20674-20684. (30) Bai, F.; Huang, H.; Hou, C.; Zhang, P., Porous Carbon-Coated Cobalt Sulfide Nanocomposites Derived from Metal Organic Frameworks (MOFs) as an Advanced Oxygen Reduction Electrocatalyst. New J. Chem. 2016, 40, 1679-1684. (31) Li, Z.; Shao, M.; Zhou, L.; Zhang, R.; Zhang, C.; Wei, M.; Evans, D. G.; Duan, X., Directed Growth of Metal-Organic Frameworks and Their Derived Carbon-Based Network for Efficient Electrocatalytic Oxygen Reduction. Adv. Mater. 2016, 28, 2337-2344. (32) Lu, Q.; Zhao, M.; Chen, J.; Chen, B.; Tan, C.; Zhang, X.; Huang, Y.; Yang, J.; Cao, F.; Yu, Y.; Ping, J.; Zhang, Z.; Wu, X. J.; Zhang, H., In Situ Synthesis of Metal Sulfide Nanoparticles Based on 2D Metal-Organic Framework Nanosheets. Small 2016, 12, 4669-4674. (33) Yu, X.; Zhang, M.; Chen, J.; Li, Y.; Shi, G., Nitrogen and Sulfur Codoped Graphite Foam as a Self-Supported Metal-Free Electrocatalytic Electrode for Water Oxidation. Adv. Energy. Mater. 2016, 6, 1501492. (34) Zhu, Q. L.; Xia, W.; Akita, T.; Zou, R.; Xu, Q., Metal-Organic Framework-Derived Honeycomb-Like Open Porous Nanostructures as Precious-Metal-Free Catalysts for Highly Efficient Oxygen Electroreduction. Adv. Mater. 2016, 28, 6391-6398 (35) Yang, L.; Gao, M.; Dai, B.; Guo, X.; Liu, Z.; Peng, B., An Efficient NiS@N/S-C Hybrid Oxygen Evolution Electrocatalyst Derived from Metal-Organic Framework. Electrochim. Acta

2016, 191, 813-820.


28

Page 29 of 33

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


(36) Jia, H.-P.; Li, W.; Ju, Z.-F.; Zhang, J., Synthesis, Structure and Magnetism of MetalOrganic Framework Materials with Doubly Pillared Layers. Eur. J. Inorg. Chem. 2006, 42644270. (37) Wen, L.; Lu, Z.; Lin, J.; Tian, Z.; Zhu, H.; Meng, Q., Syntheses, Structures, and Physical Properties of Three

Novel Metal-Organic

Frameworks Constructed from

Aromatic

Polycarboxylate Acids and Flexible Imidazole-Based Synthons. Cryst. Growth Des. 2007, 7, 9399. (38) Zhao, S.; Yin, H.; Du, L.; He, L.; Zhao, K.; Chang, L.; Yin, G.; Zhao, H.; Liu, S.; Tang, Z., Carbonized Nanoscale Metal-Organic Frameworks as High Performance Electrocatalyst for Oxygen Reduction Reaction. ACS Nano 2014, 8, 12660-12668. (39) Hou, Y.; Huang, T. Z.; Wen, Z. H.; Mao, S.; Cui, S. M.; Chen, J. H., Metal-Organic Framework-Derived Nitrogen-Doped Core-Shell-Structured Porous Fe/Fe3C@C Nanoboxes Supported on Graphene Sheets for Efficient Oxygen Reduction Reactions. Adv. Energy. Mater.

2014, 4, 1400337. (40) Li, Q.; Pan, H.; Higgins, D.; Cao, R.; Zhang, G.; Lv, H.; Wu, K.; Cho, J.; Wu, G., MetalOrganic Framework-Derived Bamboo-Like Nitrogen-Doped Graphene Tubes as an Active Matrix for Hybrid Oxygen-Reduction Electrocatalysts. Small 2015, 11, 1443-1452. (41) Hu, H.; Han, L.; Yu, M.; Wang, Z.; Lou, X. W., Metal–Organic-Framework-Engaged Formation of Co Nanoparticle-Embedded Carbon@Co9S8 Double-Shelled Nanocages for Efficient Oxygen Reduction. Energy Environ. Sci. 2016, 9, 107-111. (42) Wang, G.; Wang, H.; Wang, H.; Bai, J., Composites of Amorphous Carbon NanotubeModified Reduced Graphene Oxide Synthesized by Ethanol Decomposition and Electrochemical Evaluation of Their Lithium Storage Properties. J. Mater. Sci. 2016, 51, 5529-5544.


29


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

Page 30 of 33

(43) Lin, H.; Shi, Z.; He, S.; Yu, X.; Wang, S.; Gao, Q.; Tang, Y., Heteronanowires of MoC– Mo2C as Efficient Electrocatalysts for Hydrogen Evolution Reaction. Chem. Sci 2016, 7, 33993405. (44) Xia, W.; Zou, R. Q.; An, L.; Xia, D. G.; Guo, S. J., A Metal-Organic Framework Route to in Situ Encapsulation of Co@Co3O4@C Core@Bishell Nanoparticles into a Highly Ordered Porous Carbon Matrix for Oxygen Reduction. Energy Environ. Sci. 2015, 8, 568-576. (45) Liang, J.; Jiao, Y.; Jaroniec, M.; Qiao, S. Z., Sulfur and Nitrogen Dual‐Doped Mesoporous Graphene Electrocatalyst for Oxygen Reduction with Synergistically Enhanced Performance. Angew. Chem. Int. Ed. 2012, 51, 11496-11500. (46) Dai, L.; Xue, Y.; Qu, L.; Choi, H. J.; Baek, J. B., Metal-Free Catalysts for Oxygen Reduction Reaction. Chem. Rev. 2015, 115, 4823-4892. (47) Guo, D.; Shibuya, R.; Akiba, C.; Saji, S.; Kondo, T.; Nakamura, J., Active Sites of Nitrogen-Doped Carbon Materials for Oxygen Reduction Reaction Clarified Using Model Catalysts. Science 2016, 351, 361-365. (48) Zhu, H.; Zhang, J.; Yanzhang, R.; Du, M.; Wang, Q.; Gao, G.; Wu, J.; Wu, G.; Zhang, M.; Liu, B.; Yao, J.; Zhang, X., When Cubic Cobalt Sulfide Meets Layered Molybdenum Disulfide: A Core-Shell System toward Synergetic Electrocatalytic Water Splitting. Adv. Mater. 2015, 27, 4752-4759. (49) Liang, H.-W.; Wei, W.; Wu, Z.-S.; Feng, X.; Müllen, K., Mesoporous Metal–NitrogenDoped Carbon Electrocatalysts for Highly Efficient Oxygen Reduction Reaction. J. Am. Chem. Soc. 2013, 135, 16002-16005. (50) Wei, J.; Liang, Y.; Hu, Y.; Kong, B.; Simon, G. P.; Zhang, J.; Jiang, S. P.; Wang, H., A Versatile Iron-Tannin-Framework Ink Coating Strategy to Fabricate Biomass-Derived Iron


30

Page 31 of 33

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


Carbide/Fe-N-Carbon Catalysts for Efficient Oxygen Reduction. Angew. Chem. Int. Ed. 2016, 55, 1355-1359. (51) Wang, H.; Li, Z.; Li, G.; Peng, F.; Yu, H., Co3S4/NCNTs: A Catalyst for Oxygen Evolution Reaction. Catal. Today 2015, 245, 74-78. (52) Gu, W.; Hu, L.; Hong, W.; Jia, X.; Li, J.; Wang, E., Noble-Metal-Free Co3S4–S/G Porous Hybrids as an Efficient Electrocatalyst for Oxygen Reduction Reaction. Chem. Sci. 2016, 7, 4167-4173. (53) Liu, Q.; Wang, Y.; Dai, L.; Yao, J., Scalable Fabrication of Nanoporous Carbon Fiber Films as Bifunctional Catalytic Electrodes for Flexible Zn-Air Batteries. Adv. Mater. 2016, 28, 30003006. (54) Li, C.; Han, X.; Cheng, F.; Hu, Y.; Chen, C.; Chen, J., Phase and Composition Controllable Synthesis of Cobalt Manganese Spinel Nanoparticles Towards Efficient Oxygen Electrocatalysis. Nat Commun. 2015, 6, 7345. (55) Li, G.; Wang, X.; Fu, J.; Li, J.; Park, M. G.; Zhang, Y.; Lui, G.; Chen, Z., PomegranateInspired Design of Highly Active and Durable Bifunctional Electrocatalysts for Rechargeable Metal–Air Batteries. Angew. Chem. Int. Ed. 2016, 55, 4977-4982.

TOC Graphic and Synopsis:


31


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 32 of 33

Co/CoxSy@S,N-doped carbon composites derived from controllably grown S, N-containing CoMOFs, exhibiting bifunctional electrocatalytic activities toward ORR/OER and high performance of rechargeable zinc-air batteries.


32

Page 33 of 33

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


Co/CoxSy@S,N-doped carbon composites derived from controllably grown S, N-containing Co-MOFs, exhibiting bifunctional electrocatalytic activities toward ORR/OER and high performance of rechargeable zinc-air batteries.


CoxSy@S,N-Codoped Porous Carbon

Recommend Documents