Synthesis of NiCo Alloy Nanoparticle-Decorated B,N-Doped Carbon

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Letter

Synthesis of NiCo Alloy Nanoparticles Decorated B, N– doped Carbon Nanosheet Networks via a Self-template Strategy for Bifunctional Oxygen-involving Reactions Chunlin Yu, Shaoyun Hao, Lecheng Lei, and Xingwang Zhang ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.9b04164 • Publication Date (Web): 17 Aug 2019 Downloaded from pubs.acs.org on August 19, 2019

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ACS Sustainable Chemistry & Engineering

Synthesis of NiCo Alloy Nanoparticles Decorated B, N–doped Carbon Nanosheet Networks via a Self-template Strategy for Bifunctional Oxygen-involving Reactions Chunlin Yu,† Shaoyun Hao,† Lecheng Lei, Xingwang Zhang* Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Zheda Road No. 38, 310027, Hangzhou, China † These authors contributed equally to this work. * Corresponding author, Email: [email protected]

Abstract Developing non-precious metal catalysts for oxygen electrocatalysis is vital for next-generation energy conversion devices. Herein, a uniform distribution of NiCo alloy nanoparticles wrapped by B, N co-doped carbon nanosheet networks (core-shell structure) through a novel self-template strategy is developed (designated as NiCo@BNC). The optimal NiCo@BNC prepared at 800 ℃ (NiCo@BNC-800) shows an outstanding bifunctional ORR/OER activity with an extremely small potential difference of 0.61 V between EORR1/2 and EOER10, which is the best record so far. Theoretical calculation reveals reaction intermediates were liable to absorbed to B-sites, and Gibbs free energetics (ΔG) of NiCo@BNC-800 is more close to the ideal pathway. This facile and general strategy provides a promising avenue for rational design of transition-metal compounds for oxygen-involving reactions. Keywords: B, N co-doped carbon nanosheets; NiCo alloy nanoparticles; 1|Page

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Self-template, Bifunctional electrocatalysts; DFT calculations.

Introduction Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are the most technologically

and

fundamentally

important

electrochemical

reactions

of

oxygen-involving energy conversion devices, including fuel cells, metal-air batteries, and water electrolyzers.1-3 Nevertheless, the sluggish kinetics of the two reactions is considered as the main reason for low energy-conversion efficiency due to the reactions are stepwise four-electron process, which possess high overpotential.4-5 Precious Pt and Ir-based nanomaterials as the best-performing catalysts for ORR and OER respectively suffered from unsatisfying durability, high cost, and scarcity which greatly restricted their commercial application.6 The earth abundant transition metal-based electrocatalysts are considered as the potential substitutes for the precious metal catalysts, and only a few of them have the bifunctional catalytic property. In this regard, it still remains a critical issue to design and develop the electrocatalysts with high bifunctional intrinsic activity.4, 7-8 The non-precious bimetallic materials, particularly the transitional metals alloy nanoparticles have been mainly focused and put in the forefront used as the electrochemical catalysts for ORR and OER,9-12 but the agglomeration and direct exposure to electrolytes inevitably cause the decrease of active sites.13-15 Therefore, it is crucial to confine TMs nanoparticles with a protective layer to a limited space. To date, carbon nanomaterials such as graphene and carbon nanosheets have aroused 2|Page


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increasing attention in being a carrier for electrochemical energy devices due to their excellent stability, superior electrical conductivity and high surface area.16-17 Furthermore, heteroatoms such as B, N, P and so on could be doped into the carbon framework during the pyrolysis process, which modulate the surface polarities and electronic

structure

and

dramatically

boosts

the

performance

of

oxygen

electrocatalysis of carbon nanomaterials.18-21 Lately, metal-organic frameworks (MOFs), biomass, and polymer-derived metals decorated carbon nanosheets by pyrolysis shows the great potential in electrocatalytic applications.22-25 However, these granular or bulk precursors are liable to form the agglomerate structure with limited surface area, which goes against acquisition of enough catalytically active sites.26 Moreover, only a few of products could achieve the ideal bifunctional ORR/OER performance.10,

27

On accounts of the metal precursors could affect the

formation of carbon nanosheets, it is challenging to realize the synergism between alloy nanoparticles and carbon nanosheets.4,

28

In regard of this, it is of great

significance to develop a facile method to synthesize the alloys nanoparticles decorated heteroatom-doped carbon nanosheets with high catalytic performance towards oxygen-involving reactions. With due consideration above mentioned, we proposed a novel approach to fabricate alloy nanoparticles decorated B, N co-doped carbon nanosheet networks (BNC) with open space, where Co-B nanosheets served as the template and metal phthalocyanine as the precursors of metal alloy, carbon framework and nitrogen. Benefiting from the synergistic effect of NiCo alloy and BNC, the optimal 3|Page



NiCo@BNC prepared at 800 ℃ (NiCo@BNC-800) presents distinguished bifunctional ORR/OER activities, which exceeds the ideal catalysts of commercial Pt/C and IrO2. Theoretical calculation reveals the synergistic effect of NiCo alloy NPs and BNC contributes to the high activity of ORR. Our strategy opens a general and facile path for synthesizing bifunctional ORR/OER electrocatalysts, and paves the way of practical oxygen-involving energy conversion devices.

EXPERIMENTAL SECTIONS Synthesis of Co-B nanosheets. Co-B nanosheets were prepared by a facile reduction of NaBH4. Typically, 5 mmol Co(NO3)2·6H2O was dispersed into 50 mL H2O in a three-necked flask maintained at 0 ºC with N2 flushing in order to remove the dissolved oxygen. Next, a 0.5 M NaBH4 in 0.1 M NaOH solution was slowly injected into the Co(NO3)2 solution. With vigorous stirring, the solution turned to deep blue which means the precipitate of Co-B was synthetized. Then the Co-B precipitate was collected by centrifugation, and washed with ethanol and water for several times, dried at 60 ºC in a vacuum oven at last. Synthesis of Co or Co-M (M=Ni, Fe) alloy nanoparticles encapsulated in B, N– doped carbon nanosheet networks. Co-B nanosheets served as the template to synthesize Co-M (M=Ni, Co) alloy nanoparticles encapsulated in B, N–doped carbon nanosheets. Typically, 20 mg Co-B and 20 mg MPc (M=Co, Ni, Fe) was dispersed in 20 mL ethanol by ultrasonication for 2h at 30 ºC. Then the MPc solution was added into Co-B dispersion liquid with vigorous stirring at 1600 rpm for 24 h. The obtained powder was washed with ethanol for several times and dried at 60 ºC in a vacuum 4|Page


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oven. After that, pyrolysis process was taken with a heating ramp rate of 2 ºC/min to 800 ºC, and maintained for 2 h. Meanwhile, a series of temperature gradients of 400 ºC, 600 ºC, 1000 ºC were also taken to investigate the differences, and denoted as NiCo@BNC-x (x = 400, 600, 800, 1000 ºC).

Results and Discussion

Scheme 1. Schematic illustration of the fabricaiton of NiCo@BNC. The synthesis process of NiCo alloy nanoparticles (NPs) decorated B, N-doped carbon nanosheet networks (BNC) is elucidated in Scheme 1 (See the detailed steps in Supporting Information). Firstly, Co-B nanosheets served as the template was prepared through the reaction between cobalt cation solution and NaBH4. It was seen that Co-B nanosheets with ~ 10 nm in thickness are self-assemble together spontaneously as shown in Figure 1a and Figure S1-S3. Secondly, N-rich nickel phthalocyaninate (NiPc) was dispersed on the surface of Co-B nanosheets with stirring. Finally, the unique structure with NiCo alloy NPs decorated BNC was well formed after a pyrolysis process in argon atmosphere. After systematically researching the effect of annealing temperatures, the resultant material with temperature of 800 °C (denoted as NiCo@BNC-800) displayed the optimal 5|Page



electrochemical performance.

Figure 1. (a) SEM image of Co-B (inset is the partial enlarged image). (b) SEM image of NiCo@BNC-800. (c, d) TEM and HRTEM image of NiCo@BNC-800, inset in (d) is the calculated FFT pattern. (e) HAADF and corresponding EDS mapping images of NiCo@BNC-800. Figure 1b and 1c illustrate the morphology of NiCo@BNC-800 that NiCo alloy NPs are uniformly embedded in BNC with a size of 20-40 nm. High-resolution TEM (HRTEM) characterization in Figure 1d also demonstrates that NiCo alloy NPs are encapsulated by a few layers of BNC shell. The lattice fringes display the d-spacing of 2.15 Å and 3.37 Å, which correspond to the (111) plane of NiCo alloy and (002) plane of graphitic carbon respectively.13,

29

And the Fast Fourier transform (FFT)

confirms the lattice fringes of NiCo alloy is assigned to the (111) facet. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) elemental mapping illustrates the uniform distribution of B, N dopants in the carbon framework, while the Ni, Co signals could only be detected on NiCo alloy NPs in Figure 1e. The EDS line-scan profile (Figure S4a) along the NiCo alloy NPs further demonstrates the favorable graphitic carbon layer for NiCo alloy NPs, and the approximate molar ratio of 3: 1 for Co and Ni has been detected (Figure S4b). In addition, the SEM images and the Brunauer-Emmett-Teller (BET) specific surface 6|Page


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area of NiCo@BNC-x (x= 400, 600, 1000 °C) were also investigated in Figure S5 and S6, respectively, which illustrates the reaction temperatures have the significant influence on such unique structure. In addition, bare CoB and NiPc are also annealed at 800 °C. In Figure S7a-b, Co-B nanosheets are seriously destroyed after the pyrolysis process without the effect of NiPc which adequately illustrates the important role of NiPc in forming the unique NPs decorated carbon nanosheet structure. And the morphological difference of NiPc before and after annealing process is shown in Figure S7c-d.

Figure 2. (a) XRD pattern of NiCo@BNC-800. (b) Raman spectrum of NiCo@BNC-800. (c, d, e, f) N 1s, B 1s, Co 2p, and Ni 2p high-resolution XPS spectra of NiCo@BNC-800, respectively. The XRD pattern (Figure 2a) of NiCo@BNC-800 presents three characteristic peaks at 44.5°, 51.7° and 76.1°, which are corresponding to the (111), (200), and (220) planes of metallic NiCo alloy. And the broad peak at 26° could be assigned to the (002) plane of graphitic carbon,13, 27 which are in good agreement with HRTEM results. Furthermore, the XRD patterns of NiCo@BNC-x (x= 400, 600, 1000 °C) were also displayed in Figure S8. Figure 2b reveals the Raman spectrum of 7|Page



as-prepared NiCo@BNC-800. Two characteristic peaks at around 1330 cm-1 (D-band) and 1590 cm-1 (G-band) imply the existence of disordered and graphitized carbon.30 And the high ID/IG ratio (1.50) indicates the introduction of B, N elements create the largest quantity of defects in carbon nanosheet networks at 800 °C (other temperatures in Figure S9). The elemental compositions and the corresponding chemical states were studied by X-ray photoelectron spectroscopy (XPS). In Figure S10, the XPS survey implies the presence of Ni, Co, B, N and C in NiCo@BNC-800, and it contains 0.58, 1.75, 8.44, and 9.28 at% of Ni, Co, B and N based on the XPS survey spectra, respectively. The Ni and Co content of NiCo@BNC-800 are 0.31 wt% and 1.25 wt% by Inductively coupled plasma optical emission spectrometer (ICP-OES). As shown in Figure 2c, the N 1s spectrum of NiCo@BNC-800 is deconvoluted into three peaks at 397.4 eV, 398.6 eV, and 400.2 eV, which are assigned to B-N, pyridinic N, and graphitic N, respectively. B-N shows the maximum amount among the different N species in NiCo@BNC-x (x = 600, 800, 1000), and the ratios of B-N and pyridinic N in NiCo@BNC-800 are up to 51.6% and 26.1 % (Table S1) which are benefit for electrochemical process of ORR/OER.30-31 Meanwhile, B 1s spectrum (Figure 2d) of NiCo@BNC-800 exhibits two principal peaks at 188.6 eV and 191.1 eV corresponding to BC3 and B-N bonds, respectively. Besides that, another weak peak at 192.1 eV is attributed to the B-O bond.19 All of the N and B spectra further indicate the successfully doping of N, B elements in carbon framework under the condition of over 600 °C (Figure S11). The core level XPS of Co spectrum (Figure 2e) exhibits metallic Co with binding energies of 777.4 eV and 792.4 eV, which are assigned to the Co0 in NiCo alloy. It also shows the presence of Co3+ species (780.3 eV and 793.9 eV for 2p3/2 and 2p1/2) and Co2+ species (782.5 eV and 796.4 eV for 2p3/2 and 2p1/2) 8|Page


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with shakeup satellites (785.5 eV and 802.1 eV). Similarly, the core level XPS of Ni spectrum shows the Ni0 with binding energies of 852.0 eV and 870.6 eV in NiCo alloy,27 and the presence of Ni3+ species (853.8 eV and 871.3 eV for 2p3/2 and 2p1/2) and Ni2+ species (855.1 eV and 874.5 eV for 2p3/2 and 2p1/2) with shakeup satellites (860.7 eV and 880.9 eV) in Figure 2f, the existence of Ni2+/Ni3+ probably due to the NiPc has not been completely reduced. In addition, Co@BNC-800 and FeCo@BNC-800 were also successfully prepared by using cobalt phthalocyaninate (CoPc) and iron phthalocyaninate (FePc) in the same way as shown in Figure S12. Interestingly, the elemental composition of NPs is based on what kind of metal phthalocyaninate is used, which adequately explains our self-template method can be a general route to synthesize such unique structure.

Figure 3. (a) LSV curves of NiCo@BNC-800, and Pt/C in O2-saturated 0.1 M KOH solution. (b) The corresponding Tafel slope plots. (c) LSV curves of NiCo@BNC-800 at different rotation rates in O2-saturated 0.1 M KOH solution. (d) The top curve is current-time chronoamperometric response of NiCo@BNC-800 and Pt/C, the bottom is chronoamperometric response of NiCo@BNC-800 and Pt/C followed by addition of 3 M methanol. (e) LSV curves of NiCo@BNC-800, and IrO2 for OER reaction. (f) EOER10 and EORR1/2 gap of NiCo@BNC-800 and IrO2 + Pt/C. Linear sweep voltammetry (LSV) measurement is performed to further investigate 9|Page



their electrocatalytic activities. As shown in Figure 3a and Figure S13, NiCo@BNC-800 exhibits optimal ORR activity with an onset potential (Eonset) of 1.03 V, a half-wave potential (EORR1/2) of 0.85 V, and the limited current density (Jlimited) of 5.9 mA/cm2, which totally outperforms commercial Pt/C (Eonset: 0.97 V, EORR1/2: 0.83V, Jlimited: 5.8 mA/cm2), making it a first-rate alkaline ORR electrocatalyst (Table S2). Furthermore, the Cyclic voltammetry (CV) measurement of as-prepared NiCo@BNC catalysts were shown in Figure S14. Moreover, NiCo@BNC-800 exhibits a much lower Tafel slope value of 40 mV/dec than that of commercial Pt/C (73 mV/dec) at a low overpotential, confirming its favourable kinetic process of ORR (Figure 3b).32 To investigate the kinetic parameters of ORR process catalyzed by NiCo@BNC-800, different rotating speeds from 400 to 2000 rpm were taken out in Figure 3c.31 The corresponding Koutecky-Levich (K-L) plots based on above LSV curves at different rotation speeds in Figure S15 show an average transferred electron number of 3.95, and a small ratio (≈ 5%) of H2O2 yield was obtained from the rotating ring-disk electrode (RRDE) test in Figure S16, implying oxygen molecules are reduced to water directly with the four-electron pathway.33 In Figure 3d, NiCo@BNC-800 exhibits a favorable stability with 91.6% retention of initial current density, while Pt/C only maintains 74% retention after 30000 s testing at 1600 rpm. Furthermore, NiCo@BNC-800 presents no obvious recession when 3 M methanol is added, indicating its favorable methanol tolerance ability. These results could be ascribed to the in-situ carbonization layer enwraps NiCo alloy NPs, which protects NiCo alloy NPs from directly contacting with electrolyte during the ORR testing. In addition, the ORR performance of Co@BNC-800 and FeCo@BNC-800 are also tested in Figure S17. The electrocatalytical alkaline OER performances of NiCo@BNC catalysts with 10|Page


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different temperatures were further evaluated in 1 M KOH. As shown in Figure 3e and Figure S18, the polarization curve of as-prepared NiCo@BNC-800 exhibits a current density of 10 mA/cm2 with a small overpotential of 230 mV, which outperforms commercial IrO2 (overpotential: 250 mV). In addition, NiCo@BNC-800 exhibits a Tafel slope value of 74 mV/dec (Figure S19), which is much lower than 137 mV/dec (IrO2). Furthermore, Figure S20 shows the long-term stability of NiCo@BNC-800 with no distinct difference of overpotential to achieve the current density of 10 mA/cm2 after 40000 s. These results suggest NiCo@BNC-800 is also an excellent OER electrocatalyst in alkaline electrolyte (Table S2). Based on the above superb catalytic performance towards ORR and OER, the bifunctional catalytic activity of NiCo@BNC-800 is evaluated by the ΔE between EORR1/2 (potential of current density at 3 mA/cm2) and EOER10 (potential of current density at 10 mA/cm2). As shown in Figure 3f, NiCo@BNC-800 displays the measured value of 0.61 V, which is much lower than of IrO2 + Pt/C (0.74 V). Of note, the ΔE of NiCo@BNC-800 is the best record among recent reports (Table S2). Density functional theory (DFT) calculation was taken to investigate the reason of the excellent ORR electrocatalytic activity of NiCo@BNC-800 (Computational details are in the Supporting Information). The ORR activity on bare NiCo alloy NPs surface was examined firstly, and the oxygen binding energy on the NiCo alloy NPs is about 6.3 eV. When we optimized the OOH* on the surface of NiCo alloy NPs, the OOH* tends to decompose into O* and *OH species, therefore the result suggests bare NiCo alloy NPs is not a promising candidate for ORR as it suffers from too strong oxygen binding energy.34 After that, a slab model was used to represent NiCo@BNC-800 surface, while the BNC was used to represent NiCo@BNC-800 after acid-etching.35 11|Page



Figure 4. (a) The proposed reaction pathways for ORR of BNC (top) and NiCo@BNC-800 (bottom) during the oxygen reduction reaction. (b) Free energy diagram for the four-electron associative ORR of BNC and NiCo@BNC-800 at U = 0 V. As shown in Figure 4a, B-sites were adopt to investigate the Gibbs free energetics (ΔG) due to the reaction intermediate of OOH*, O* and *OH were liable to absorbed to B-sites after calculation.36 Based on the calculated results (Table S3), the free energy diagram of each step for ORR pathway is shown in Figure 4b. The ΔG of NiCo@BNC-800 is much closer to the ideal pathway compared with BNC, implying NiCo@BNC-800 is more favorable than that of BNC in the whole ORR process. In the computational hydrogen electrode (CHE) model, the theoretical overpotential is a direct indicator to evaluate the activity of catalyst. The calculated theoretical overpotential of BNC is about 0.31 V while only about 0.22 V for NiCo@BNC-800, which further explains the synergistic effect of NiCo alloy NPs and BNC contributes to the high activity towards ORR reaction. In addition, the free energy diagram of NiCo@BNC-800 at U = 1.23 V as presented in Figure S21, it shows an uphill sequence which corresponds to the rate-determining step of ORR process from O* to *OH species.37

Conclusions 12|Page


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In summary, we presented a 2D nanosheet self-template method for fabricating bimetallic alloy nanoparticles decorated heteroatom-doped carbon nanosheet networks electrocatalysts. The optimal NiCo@BNC-800 exhibited superior ORR/OER activities with an extremely small potential difference of 0.61 V between EORR1/2 and EOER10, which exceeded most reports of carbon nanosheets decorated with single metal or bimetallic alloys. Due to the particular effect of NiPc in protecting the nanosheets from destroying and the in-situ B, N co-doping, large amount of active sites have been exposed. Meanwhile, the successfully synthesized of NiCo alloy encapsulated by a few layers of BNC shell which possess high electrocatalytic activity and high conductivity further facilitates the catalytic process. This work offers a novel strategy for developing highly active non-previous metal based electrocatalysts towards oxygen-involving reactions.

Supporting Information The Supporting Information is available free of charge on the ACS Publications website. SEM, TEM, HR-TEM, and elemental maps for Co-B, Co-M@BCN (M=Ni, Fe) fabricated were put in SI. The XRD patterns, XPS, and electrochemical data for these prepared electrodes were also placed in SI. AUTHOR INFORMATION Corresponding Author *Xingwang Zhang. E-mail: [email protected]

Acknowledgements Yu C. L. and Hao S. Y. contributed equally to this work. The support was received from Natural Science Foundation of China (Project No. 21776248) and Natural Science Foundation of Zhejiang Province (No. LR17B060003). Notes 13|Page



The authors declare no conflict of interest.

References (1) Xia, B. Y.; Yan, Y.; Li, N.; Wu, H.B.; Lou, X.W.; Wang, X. A metal-organic framework-derived bifunctional oxygen electrocatalyst. Nat. Energy 2016, 1: 15006. (2) Sun, J.; Lowe, S. E.; Zhang, L.; Wang, Y.; Pang, K.; Wang, Y.; Zhong, Y.; Liu, P.; Zhao, K.; Tang, Z.; Zhao, H. Ultrathin Nitrogen-Doped Holey Carbon@Graphene Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions in Alkaline and Acidic Media. Angew. Chem. Int. Ed. 2018, 130(50): 16749-16753. (3) Jiang, Z.; Jiang, Z. J.; Tian, X.; Chen, W. Amine-functionalized holey graphene as a highly active metal-free catalyst for the oxygen reduction reaction. J. Mater. Chem. A 2014, 2(2): 441-450. (4) Wang, H. F.; Tang, C.; Zhang Q. A Review of Precious-Metal-Free Bifunctional Oxygen Electrocatalysts: Rational Design and Applications in Zn-Air Batteries. Adv. Funct. Mater. 2018, 28(46): 1803329. (5) Jiao, Y.; Zheng, Y.; Jaroniec, M.; Qiao S. Z. Design of electrocatalysts for oxygen- and hydrogen-involving energy conversion reactions. Chem. Soc. Rev. 2015, 44(8): 2060-2086. (6) Yu, J.; Chen, G.; Sunarso, J.; Zhu, Y.; Ran, R.; Zhu, Z.; Zhou, W.; Shao, Z. Cobalt Oxide and Cobalt-Graphitic Carbon Core-Shell Based Catalysts with Remarkably High Oxygen Reduction Reaction Activity. Adv. Sci. 2016, 3(9): 14|Page


Page 14 of 20

Page 15 of 20 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


1600060. (7) Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature 2012, 486: 43-51. (8) Chen, P.; Zhou, T.; Xing, L.; Xu, K.; Tong, Y.; Xie, H.; Zhang, L.; Yan, W.; Chu, W.; Wu, C.; Xie, Y. Atomically Dispersed Iron-Nitrogen Species as Electrocatalysts for Bifunctional Oxygen Evolution and Reduction Reactions. Angew. Chem. Int. Ed. 2017, 56(2): 610-614. (9) Wu, L.; Li, Q.; Wu, C. H.; Zhu, H.; Mendoza, G. A.; Shen, B.; Guo, J.; Sun, S. Stable Cobalt Nanoparticles and Their Monolayer Array as an Efficient Electrocatalyst for Oxygen Evolution Reaction. J. Am. Chem. Soc. 2015, 137(22): 7071-7074. (10)Wang, X. R.; Liu, J. Y.; Liu, Z. W.; Wang, W. C.; Luo, J.; Han, X. P.; Du, X. W.; Qiao, S. Z.; Yang, J. Identifying the Key Role of Pyridinic-N-Co Bonding in Synergistic Electrocatalysis for Reversible ORR/OER. Adv. Mater. 2018, 30(23): 1800005. (11)Hao S.; Chen L.; Yu C.; Yang B.; Li Z.; Hou Y.; Lei L., Zhang X., Nicomo Hydroxide Nanosheet Arrays Synthesized Via Chloride Corrosion for Overall Water Splitting. ACS Energy Lett. 2019, 4 (4), 952-959. (12)Liu W.; Liu H.; Dang L.; Zhang H.; Wu X.; Yang B.; Li Z.; Zhang X.; Lei L., Jin S., Amorphous Cobalt–Iron Hydroxide Nanosheet Electrocatalyst for Efficient Electrochemical and Photo-Electrochemical Oxygen Evolution. Adv. Funct. Mater. 2017, 27 (14), 1603904. 15|Page



Page 16 of 20

(13)Deng, J.; Ren, P.; Deng, D.; Bao X. Enhanced Electron Penetration through an Ultrathin Graphene Layer for Highly Efficient Catalysis of the Hydrogen Evolution Reaction. Angew. Chem. Int. Ed. 2015, 54(7): 2100-2104. (14)Cui, X.; Ren, P.; Deng, D.; Deng, J.; Bao, X. Single layer graphene encapsulating non-precious metals as high-performance electrocatalysts for water oxidation. Energy Environ. Sci. 2016, 9(1): 123-129. (15)Hu,

H.;

Han,

L.;

Yu,

organic-framework-engaged

M.;

Wang,

formation

of

Z.;

Lou,

X.W.

Metal–

Co

nanoparticle-embedded

carbon@Co9S8 double-shelled nanocages for efficient oxygen reduction. Energy Environ. Sci. 2016, 9(1): 107-111. (16)Wei, W.; Liang, H.; Parvez, K.; Zhuang, X.; Feng, X.; Müllen, K. Nitrogen-Doped Carbon Nanosheets with Size-Defined Mesopores as Highly Efficient Metal-Free Catalyst for the Oxygen Reduction Reaction. Angew. Chem. Int. Ed. 2014, 126(6): 1596-1600. (17)Su, H.; Zhang, K. X.; Zhang, B.; Wang, H. H.; Yu, Q. Y.; Li, X. H.; Antonietti, M.; Chen, J. S. Activating Cobalt Nanoparticles via the Mott–Schottky Effect in Nitrogen-Rich Carbon Shells for Base-Free Aerobic Oxidation of Alcohols to Esters. J. Am. Chem. Soc. 2017, 139(2): 811-818. (18)Liu, X.; Dai, L. Carbon-based metal-free catalysts. Nat. Rev. Mater. 2016, 1: 16064. (19)Yuan, K.; Sfaelou, S.; Qiu, M.; Lützenkirchen, H. D.; Zhuang, X.; Chen, Y.; Yuan, C.; Feng, X.; Scherf, U. Synergetic Contribution of Boron and Fe-Nx 16|Page


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Species in Porous Carbons toward Efficient Electrocatalysts for Oxygen Reduction Reaction. ACS Energy Lett. 2018, 3(1): 252-260. (20)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(10): 2839-2855. (21)Rao, C. N.; Gopalakrishnan, K.; Govindaraj, A. Synthesis, properties and applications of graphene doped with boron, nitrogen and other elements. Nano Today 2014, 9(3): 324-343. (22)Xu, Y.; Jin, S.; Xu, H.; Nagai, A.; Jiang, D. Conjugated microporous polymers: design, synthesis and application. Chem. Soc. Rev. 2013, 42(20): 8012-8031. (23)Zhang, J.; Chen, G.; Müllen, K.; Feng, X. Carbon-Rich Nanomaterials: Fascinating Hydrogen and Oxygen Electrocatalysts. Adv. Mater. 2018, 30(40): 1800528. (24)Wu, G.; More, K. L.; Johnston, C. M.; Zelenay, P. High-Performance Electrocatalysts for Oxygen Reduction Derived from Polyaniline, Iron, and Cobalt. Science 2011, 332(6028): 443-447. (25)Wang, X.; Li, X.; Ou, Y. C.; Li, Z.; Dou, S.; Ma, Z.; Tao, L.; Huo, J.; Wang, S. Nonporous MOF-derived dopant-free mesoporous carbon as an efficient metal-free electrocatalyst for the oxygen reduction reaction. J. Mater. Chem. A 2016, 4(24): 9370-9374. (26)Shi, Z.; Xing, L.; Liu, Y.; Gao, Y.; Liu, J. A porous biomass-based sandwich-structured

Co3O4@Carbon

Fiber@Co3O4

17|Page


composite

for


high-performance supercapacitors. Carbon 2018, 129: 819-825. (27)Li, Z.; He, H.; Cao, H.; Sun, S.; Diao, W.; Gao, D.; Lu, P.; Zhang, S.; Guo, Z.; Li, M.; Liu, R.; Ren, D.; Liu, C.; Zhang, Y.; Yang, Z.; Jiang, J.; Zhang, G. Atomic Co/Ni dual sites and Co/Ni alloy nanoparticles in N-doped porous Janus-like carbon frameworks for bifunctional oxygen electrocatalysis. Appl. Catal. B- Environ. 2019, 240: 112-121. (28)Liu, X.; Wang, L.; Yu, P.; Tian, C.; Sun, F.; Ma, J.; Li, W.; Fu, H. A Stable Bifunctional Catalyst for Rechargeable Zinc-Air Batteries: Iron-Cobalt Nanoparticles Embedded in a Nitrogen-Doped 3D Carbon Matrix. Angew. Chem. Int. Ed. 2018, 130(49): 16398-16402. (29)Weng, C. C.; Ren, J. T.; Hu, Z. P.; Yuan, Z. Y. Nitrogen-Doped Defect-Rich Graphitic Carbon Nanorings with CoOx Nanoparticles as Highly Efficient Electrocatalyst for Oxygen Electrochemistry. ACS Sustain. Chem. Eng. 2018, 6(11): 15811-15821. (30)Lu, Z.; Wang, J.; Huang, S.; Hou, Y.; Li, Y.; Zhao, Y.; Mu, S.; Zhang, J.; Zhao, Y. N,B-codoped defect-rich graphitic carbon nanocages as high performance multifunctional electrocatalysts. Nano Energy 2017, 42: 334-340. (31)Su, C. Y.; Cheng, H.; Li, W.; Liu, Z. Q.; Li, N.; Hou, Z.; Bai, F. Q.; Zhang, H. X.; Ma, T. Y. Atomic Modulation of FeCo-Nitrogen-Carbon Bifunctional Oxygen Electrodes for Rechargeable and Flexible All-Solid-State Zinc-Air Battery. Adv. Energy Mater. 2017, 7(13): 1602420. (32)Zhu, C.; Shi, Q.; Xu, B. Z.; Fu, S.; Wan, G.; Yang, C.; Yao, S.; Song, J.; Zhou, 18|Page


Page 18 of 20

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H.; Du, D.; Beckman, S. P.; Su, D.; Lin, Y. Hierarchically Porous M-N-C (M = Co and Fe) Single-Atom Electrocatalysts with Robust MNx Active Moieties Enable Enhanced ORR Performance. Adv. Energy Mater. 2018, 8(29): 1801956. (33)Sultan, S.; Tiwari, J. N.; Jang, J. H.; Harzandi, A. M.; Salehnia, F.; Yoo, S.J.; Kim, K. S. Highly Efficient Oxygen Reduction Reaction Activity of Graphitic Tube Encapsulating Nitrided CoxFey Alloy. Adv. Energy Mater. 2018, 8(25): 1801002. (34)Shao, M.; Chang, Q.; Dodelet, J. P.; Chenitz, R. Recent Advances in Electrocatalysts for Oxygen Reduction Reaction. Chem. Rev. 2016, 116(6): 3594-3657. (35)Huang, X.; Zhang, Y.; Shen, H.; Li, W.; Shen, T.; Ali, Z.; Tang, T.; Guo, S.; Sun, Q.; Hou, Y. N-Doped Carbon Nanosheet Networks with Favorable Active Sites Triggered by Metal Nanoparticles as Bifunctional Oxygen Electrocatalysts. ACS Energy Lett. 2018, 3(12): 2914-2920. (36)Koitz, R.; Nørskov, JK.; Studt, F. A systematic study of metal-supported boron nitride materials for the oxygen reduction reaction. Phys. Chem. Chem. Phys. 2015, 17(19): 12722-12727. (37)Eslamibidgoli, M. J.; Huang, J.; Kadyk, T.; Malek, A.; Eikerling, M. How theory and simulation can drive fuel cell electrocatalysis. Nano Energy 2016, 29: 334-361.

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Graphical abstract (For Table of Contents Use Only)

A novel self-template approach is developed to synthesize alloy nanoparticles decorated B, N co-doped carbon nanosheets with outstanding bifunctional ORR/OER performance.

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Synthesis of NiCo Alloy Nanoparticle-Decorated B,N-Doped Carbon

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