Letter www.acsami.org
Morphology-Controllable Synthesis of Cobalt Telluride Branched Nanostructures on Carbon Fiber Paper as Electrocatalysts for Hydrogen Evolution Reaction Ke Wang,† Zhiguo Ye,‡ Chenqi Liu,† Dan Xi,† Chongjian Zhou,† Zhongqi Shi,*,† Hongyan Xia,† Guiwu Liu,*,§ and Guanjun Qiao†,§ †
State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049, China School of Materials Science and Engineering, Nanchang Hangkong Univerisity, Nanchang 330063, China § School of Materials Science and Engineering, Jiangsu University, Zhenjiang 212013, China ‡
S Supporting Information *
ABSTRACT: Cobalt telluride branched nanostructures on carbon fiber paper (CFP) with two different morphologies were synthesized via solution-based conversion reaction. Both the CoTe2 with nanodendrite and CoTe with nanosheet morphologies on the CoTe2 nanotube (CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs) supported by CFP exhibit high activities toward hydrogen evolution reaction (HER). Particularly, the CoTe NSs/CoTe2 NTs only require an overpotential of 230.0 mV to deliver the current density of 100 mA cm−2 in acid solution. After cycling for 5000 cycles or 20 h continual electrolysis, only a small performance loss is observed. KEYWORDS: cobalt telluride, hydrogen evolution reaction, branched nanowire, core−shell, electrocatalyst, carbon fiber paper
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increased the catalytic performance. However, the research on cobalt telluride as electrocatalyst to HER has rarely been reported. Herein, we for the first time present the facile syntheses of CoTe2 with nanodendrite and CoTe with nanosheet morphologies on the CoTe2 nanotube (CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs) supported by carbon fiber paper (CFP). The performances as electrocatalyst toward HER is also evaluated. The core materials could excellently disperse the shell materials to achieve a large surface area. More than just acting as core materials in the nanostructure, the CoTe2 along with the CoTe shows a synergistic effect in the HER process, which facilitates the efficiency of the entire electrode. The facile synthesis includes two steps: (1) hydrothermal growth of Co(OH) (CO3)0.5 nanowires (NWs) and (2) the conversion of Co(OH) (CO3)0.5 NWs to the branched nanostructure via the conversion reaction, as illustrated in Figure 1a. The hydrothermal synthesis of well-aligned Co(OH) (CO3)0.5 NWs on CFP coincides with our previous reports.8,17 The X-ray diffraction (XRD) pattern, scanning electron microscope (SEM) and transmission electron microscope (TEM) images of Co(OH) (CO3)0.5 NWs are presented in
lectrochemical splitting of water into hydrogen fuel and oxygen byproduct has been proven to be a facile and effective method in the production of hydrogen.1,2 In acid electrolyte, the Pt group noble metals exhibit the excellent catalytic activities toward hydrogen evolution reaction (HER), whereas the small reservation and high price severely hamper the widespread applications. Therefore, the key to implement the electrolysis in large-scale practical hydrogen preparation is finding an efficient electrocatalyst to replace the Pt group materials.3−5 The effective strategies to improve the efficiency of electrocatalysts for HER include component modifications and nanostructure design.6−8 Cobalt telluride with the general formula of CoTex has been synthesized with a variety of different morphologies.9−12 They have been reported to show high performance as electrocatalysts to oxygen reduction reaction (ORR),13 oxygen evolution reaction (OER),14 electrocatalysts for CO2 reduction,15 and dye-sensitized solar cells.16 Other cobalt chalcogenides such as CoS2 and CoSe217,18 have been extensively investigated as electrocatalysts for HER. Liang et al.19 reported the solution-based synthesis of porous CoSe2; Caban-Acevedo et al.20 presented the Co−S−P ternary pyrite nanomaterials; Zhang et al.21 suggested the mixed phases of CoSe2 could enhance the catalytic performance; Farber et al.22,23 gave the facile method to synthesize CoS2 in high quality and compared the catalytic performances of different transition metal pyrites; Zhuo et al.24 doped Se into NiP2 and largely © 2016 American Chemical Society
Received: November 10, 2015 Accepted: January 26, 2016 Published: January 26, 2016 2910
DOI: 10.1021/acsami.5b10835 ACS Appl. Mater. Interfaces 2016, 8, 2910−2916
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ACS Applied Materials & Interfaces
Figure 1. (a) Scheme of CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs syntheses. (b) XRD patterns of CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs. High-resolution XPS spectra of (c) Co 2p and (d) Te 3d of samples.
homogeneous distribution. Moreover, the reductants are supposed to be nearly neutral in solution, because Co(OH) (CO3)0.5 NWs could hardly reserve the morphology in a too acidic or alkaline condition. Ratio of core and shell materials could be controlled by adjusting the quantity of Te source added into the autoclave. When we used 0.5 mM Na2TeO3 and 10 mL N2H4·H2O as reactants, the NW morphology could not be preserved since the Co(OH) (CO3)0.5 could dissolve in N2H4·H2O solution (Figure S2a). As presented in Figure S2b, c, when N2H4·H2O was kept at 10 mL and Na2TeO3 increased from 1 mM to 2 mM, the amounts of the CoTe2 ND shell significantly grew. Figure S2d, e exhibits the rise of CoTe NSs in quantity when we kept the molar ratio of Te to NaBH4 at 1:4 and increased the Te from 1 mM to 2 mM. However, the amounts of CoTe NSs decreased when we further increased the Te to 3 mM (Figure S2f). It was caused by the formation of Te microrods which consumed too much Te monomers in the system, as seen in the inset of the Figure S2f. XRD was used to acquire the crystal structure information on our samples and the patterns are presented in Figure 1b. The pattern of CoTe2 NDs/CoTe2 NTs matches the CoTe2 (JCPDS PDF 74−0245), whereas CoTe NSs/CoTe2 NTs show the mixed patterns of CoTe2 and CoTe (JCPDS PDF 34−0420).25 However, the quantity of CoTe NSs is much smaller than the CoTe2 cores10 and the ultrathin structure of CoTe NSs could make the diffraction intensity even weaker. There is no visible peak of the Co(OH) (CO3)0.5 NW templates indicating the templates have been fully converted to the cobalt telluride nanostructures via the conversion reaction. X-ray photoelectron spectroscopy (XPS) was employed to verify the components and valence states of electrocatalysts. Figure 1c, d presents the high-resolution XPS spectra of Co 2p and Te 3d regions. The Co 2p2/3 peaks centered at 781 and 778.5 eV are in accordance with reported data of CoTe10 and CoTe29 respectively. The corresponding Co 2p1/2 peaks at 796.9 and 793.5 eV also confirm the existences of CoTe and CoTe2 phases. The peaks labeled with letter “S” are the satellite
Figure S1. For step 2, the facile conversion reaction was conducted for the replacement of O by Te atoms where the Co(OH) (CO3)0.5 NWs acted as templates.25,26 To be specific, 2 mM Na2TeO3 and Te powder were used as Te sources for the syntheses of CoTe2 NDs/CoTe2 NTs and CoTe NSs/ CoTe2 NTs, respectively; 10 mL of 98% N2H4·H2O and 8 mM NaBH4 performed as the corresponding reductants. The CoTe2 cores were formed according to a simple ion-exchange reaction (Te2− replacing O2−).25 As the reaction proceeded, more Co2+ diffused out to the interfaces, the hollow NT structure was then achieved according to the Kirkendall effect.27,28 Although the mechanism of synthesizing the CoTe2 or CoTe shell is more complicated. The shell is formed by the reaction between Co and Te monomers according to the coreduction mechanism,12 which is controlled by the reaction kinetics. In the case of CoTe2 NDs/CoTe2 NTs nanostructure synthesis, the Co2+ is introduced by the “ion exchange reaction”, which is a relatively slow process, because the Co2+ must diffuse from the inside of nanowire. Meanwhile, the Te monomer is relatively excessive, because the water-soluble Na2TeO3 and N2H4·H2O are used as Te source and reducing agent. Therefore, the CoTe2 was formed as the shell material. On the contrary, in terms of CoTe NS synthesis, the formation of Te monomer is even slower than the Co here, because the excessive NaBH4 does not favor the existence of Te monomer (Te could dissolve in NaBH4 solution forming the soluble NaHTe). As the result, the CoTe was formed as the shell material. Considering the mechanism described above, we believe the core and shell materials experienced the simultaneous but independent formation in different positions of the nanostructure. We have also tried other combinations of common Te sources and reductants and failed to prepare well aligned core−shell nanostructure. The success in synthesis of core−shell nanostructure should be attributed to the following two reasons: (i) homogeneous distribution of Te source in the solution; (ii) the reservation of Co(OH) (CO3)0.5 NWs in the synthesis process. The Te sources have to be the dissolved ions in solution to achieve the 2911
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Figure 2. SEM images of (a, b) CoTe2 NDs/CoTe2 NTs and (d, e) CoTe NSs/CoTe2 NTs. TEM images of (c) CoTe2 NDs/CoTe2 NTs and (f) CoTe NSs/CoTe2 NTs. The STEM images, EDS element mappings of Co, Te, and O and the corresponding spectra of (g) CoTe2 NDs/CoTe2 NTs and (h) CoTe NSs/CoTe2 NTs.
peaks of Co element. The letter “O” refers to the oxidation of Co on the surface due to the low oxidation-resistance of CoTe2. Te 3d5/2 positioned at 573.3 and 573 eV are highly in agreement with the binding energy values of CoTe14,15 and CoTe29 respectively. The letter “O” represents the peaks attributed to the oxidation of Te on the surface.15 From the XPS analyses, it could be concluded that the CoTe2 NDs/ CoTe2 NTs only contain the CoTe2 phase, while the CoTe NSs/CoTe2 NTs are constituted by both CoTe and CoTe2 phases. It is also worth mentioning that the peak intensities of CoTe2 are much weaker than CoTe for the sample of CoTe NSs/CoTe2 NTs and the phenomenon is caused by different distributions of cobalt telluride: CoTe2, the core in the nanostructure, is covered by the nanostructed CoTe shell on the surface. The morphologies of CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs were investigated with SEM and TEM. Figure 2a−c clearly presents the nanostructure of CoTe2 NDs/CoTe2 NTs. The CoTe2 NTs are grown on the carbon fiber in a well aligned pattern and the CoTe2 are grown perpendicularly onto the CoTe2 NT core forming a ND morphology. As shown in Figure 2d−f, the CoTe NSs/CoTe2 NTs include a similar pattern of CoTe2 cores due to the same Co(OH) (CO3)0.5 NWs used as templates, while the CoTe exhibits a ultrathin NS morphology on the CoTe2 NTs forming a higly porous nanostructure. The scanning transmission electron microscope (STEM) and the energy-dispersive X-ray spectroscopy (EDS) equipped in the TEM were used to directly illustrate the branched nanostructure with element mappings (Figure 2g, h). To confirm the core−shell structure and the corresponding compositions, we conducted selected area electron diffraction (SAED) analyses and EDS point analyses (Figure 3). Figure 3a presents the TEM image of the CoTe2 NDs/CoTe2 NTs and the marks in it illustrate the exact places where the SAED patterns and high-resolution TEM (HRTEM) image were taken. In the SAED patterns of NT (Figure 3b) and ND (Figure 3c) we only find the CoTe2 phase and the HRTEM image (Figure 3d) clearly shows the lattice fringes with dspacing of 0.27 nm corresponding to the (012) facet of CoTe2. The CoTe2 NDs/CoTe2 NT structure was further verified by EDS point analyses. As shown in Figure 3(e, f), the atom ratios of Co to Te are nearly 1:2 on both core and shell parts. The same characterisations were conducted on CoTe NSs/CoTe2 NTs. As illustrated in Figure 3g, SAED patterns were gotten
from the shell and core respectively and the corresponding results are given in Figure 3h, f. From the patterns we could conclude that the NS only contains CoTe and the combination of CoTe and CoTe2 patterns appears when we select both the NT and NS into the interested area. The HRTEM image (Figure 3j) shows the ultrathin morphology of the NS and the lattice fringes of CoTe (002) facet with the d-spacing of 0.26 nm. As exhibited in Figure 3k, l, the EDS point analyses were performed on both the NS and NT. The atom ratio of Co to Te is nearly 1:1 on NS shell, while the atom ratio changes to 1:2 when analysis point is on the NT core. EDS line-scan analyses were also conducted on CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs, respectively, and the results are presented in Figure S3. In the case of CoTe2 NDs/CoTe2 NTs, the atom ratio of Co to Te exhibits no obvious difference between the core and shell part. However, for the sample of CoTe NSs/CoTe2 NTs, the Te to Co atom ratio shows a clear increase from nearly 1 to 2 when the position moves from shell to core. All the results firmly demonstrate the CoTe2 or CoTe shell/CoTe2 core branched nanostructures are successfully prepared. The advanced core−shell nanostructure has the following merits: (i) the CoTe2 NDs and CoTe NSs could gain large surface area for the contact with electrolyte; (ii) the core of CoTe2 NTs could also act as electrocatalysts via the synergistic effect and transfer the electrons quite fast; (iii) CFP possesses a microscale porous structure, electrochemical inertness, and high electrical conductivity, which guarantees an ideal substrate for supporting electrocatalysts. As a control group, we also synthesized the CoTe NTs on CFP according to Patil’s report.14 The XRD pattern, SEM image as well as the corresponding EDS spectrum are presented in Figure S4a−d. The HER activities of CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs were investigated with linear sweeping voltammetry (LSV) as an integrated electrode in 0.5 M H2SO4 solution at room temperature with a 3-electrode configuration. As the group for comparison, commercially available Pt/C catalyst (20 wt % Pt on Vulcan XC-72R, SigmaAldrich) and CoTe NTs on CFP were also measured in the same condition. As shown in Figure 4a, the Pt/C exhibits nearly zero overpotential to afford a cathodic current. In terms of the cobalt telluride nanostructures, the CoTe NSs/CoTe2 NTs only need the overpotential of 230.0 mV to drive a current density of 100 mV cm−2. While the CoTe2 NDs/CoTe2 NTs need the overpotential of 353.7 mV and CoTe NTs need 345.4 2912
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Figure 3. TEM images of (a) CoTe2 NDs/CoTe2 NTs and (g) CoTe NSs/CoTe2 NTs. The selected area electron diffraction (SAED) patterns of (b, c) CoTe2 NDs/CoTe2 NTs and (h, (i) CoTe NSs/CoTe2 NTs. HRTEM images of (d) CoTe2 ND and (j) CoTe NS. STEM image and corresponding EDS analyses results of (e, f) CoTe2 NDs/CoTe2 NTs and (k, l) CoTe NSs/CoTe2 NTs.
the Pt/C, which coincides with former research.17,29 Derived from the fitting of the Tafel plot, the exchange current density is usually considered to be another important parameter to describe the performance of catalysts. By calculating the x-axis intercepts of the fitted lines in the Tafel plots, the exchange current densities of the CoTe2 NDs/CoTe2 NTs, CoTe NSs/ CoTe2 NTs, and CoTe NTs are 0.131, 9.95, 0.132 μA cm−2, respectively, indicating the higher catalytic activity of the CoTe NSs/CoTe2 NTs than the others. Electrochemical impedance spectroscopy (EIS) has been proven to be an important supplement to traditional electrochemical evaluation methods. The EIS measurements were conducted at −150 mV (vs RHE) with an amplitude of 10 mV within the frequency range of 100 k to 1 Hz. The reason why the sample with NS morphology
mV to deliver the same current density. Considering the solarto-hydrogen efficiency in the solar water splitting applications, the current density of 10 mA cm−2 is chosen as one of the benchmarks in evaluating the catalytic performance.1 The overpotentials of CoTe2 NDs/CoTe2 NTs, CoTe NSs/CoTe2 NTs, and CoTe NTs needed to produce the current density of 10 mA cm−2 are 309, 172, and 284 mV respectively. Tafel slope is another important factor to evaluate the activity of electrocatalysts. A small Tafel slope is usually preferred because an interested current density could require less overpotential. As shown in Figure 4b, the CoTe NSs/CoTe2 NTs possess a smaller Tafel slope of 57.1 mV dec−1 than the ND one and CoTe NTs with the Tafel slope of 63.2 and 58.7 mV dec−1 respectively. The Tafel slope of ∼30 mV dec−1 is attributed to 2913
DOI: 10.1021/acsami.5b10835 ACS Appl. Mater. Interfaces 2016, 8, 2910−2916
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Figure 4. (a) Polarization curves; (b) corresponding Tafel plots of CoTe2 NDs/CoTe2 NTs, CoTe NSs/CoTe2 NTs, and CoTe NTs; (c) Nyquist plots and fitted curves of CoTe2 NDs/CoTe2 NTs, CoTe NSs/CoTe2 NTs, and CoTe NTs; (d) plot presenting the extraction of the double-layer capacitance (Cdl); (e) polarization curves before and after 5000 CV cycles of CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs; (f) continual electrolysis of CoTe NSs/CoTe2 NTs for 20 h at the static overpotential driving an initial current density of 50 mA cm−2.
metry (CV) performed in the potential range of 0.1 to 0.2 V (vs RHE) only involves the double-layer capacitance (Cdl). It has been proven effective to determine the Cdl to enable the comparison of the electrochemically active surface area (ECSA) between different samples.8,30 The CVs were performed at the scan rates of 10, 20, 50, 100, 200 mV s−1 and the corresponding curves are presented in Figure S7. Figure 4d plots the current density differences of anode and cathode versus the scan rates. The lines in Figure 4d are achieved by linear fitting the scatters and the Cdl was equal to half of the fitted line slopes. The Cdl of CoTe2 NDs/CoTe2 NTs, CoTe NSs/CoTe2 NTs, and CoTe NTs are 8.3, 10.9, and 8.0 mF cm−2, respectively. This result indicates the NS sample has a larger ECSA than the other two and the larger ECSA could benefit the catalytic performance for more active sites exposed to the electrolyte. In summary, the CoTe NSs/CoTe2 NTs exhibit good catalytic activity toward HER and show potential in hydrogen production applications. The higher catalytic activity of the CoTe NSs/CoTe2 NTs than the CoTe2 NDs/CoTe2 NTs and CoTe NTs is attributed to the smaller Rct as well as the larger ECSA benefiting from the advanced nanostructure. Moreover, the ultrathin CoTe NSs could promote the involvement of CoTe2 NT in the HER and improve the efficiency of the whole electrode because of the synergistic effect. The cycling performance is another critical parameter for the evaluation of electrocatalysts. To test the reversibility of our
exhibits superior performance to the other two could be explained according to the charge transfer resistance (Rct). By fitting the raw data of EIS measurements with the equivalent circuit presented in Figure S6, the values of Rct were determined. The Nyquist plots of raw data and corresponding fitting curves were presented in Figure 4c. It could be seen that the series resistances (Rs) of CoTe2 NDs/CoTe2 NTs, CoTe NSs/CoTe2 NTs, and CoTe NTs are similar and quite small (2.13, 1.95, and 1.81 Ω, respectively), which indicates the reliable electrical contact between catalysts and CFP substrate. By contrast, the Rct of CoTe NSs/CoTe2 NTs is 35.4 Ω, which is much smaller than 375.0 Ω of CoTe2 NDs/CoTe2 NTs and 305 Ω of CoTe NTs. The much smaller Rct indicates the CoTe NSs/CoTe2 NTs have a faster electron exchange rate than the counterparts. The reason why the CoTe NSs/CoTe2 NTs show a much smaller Rct than that of the CoTe2 NDs/CoTe2 NTs could be explained by the following reasons: first of all, CoTe NSs/CoTe2 NTs present larger ECSA than CoTe2 NDs/ CoTe2 NTs; second, the ultrathin structure of CoTe NS exposes more edge atoms than the ND, which is believed to exhibit high catalytic activity; third, the NS structure may contain more defects acting as active point in the structure as suggested by the HRTEM image; Moreover, we believe the ultrathin structure could introduce the core materials to participate in the HER process, which also facilitates the kinetics of hydrogen production process. The cyclic voltam2914
DOI: 10.1021/acsami.5b10835 ACS Appl. Mater. Interfaces 2016, 8, 2910−2916
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samples, CVs were performed for 5000 cycles between 0.2 V (vs RHE) and the overpotential driving a cathodic current density of ∼20 mA cm−2. The initial polarization curves and those after 5000 cycles are presented in Figure 4e. Both the CoTe2 NDs/CoTe2 NTs and CoTe NSs/CoTe2 NTs exhibit an excellent cycling performance after 5000 cycles. The gaps of overpotential driving the current density of 50 mA cm−2 between initial and last polarization curves of CoTe2 NDs/ CoTe2 NTs and CoTe NSs/CoTe2 NTs are only 12.9 and 12.5 mV, respectively. The stability of CoTe NSs/CoTe2 NTs is also tested by continual electrolysis for 20 h at a static overpotential driving an initial current density of 50 mA cm−2, as shown in Figure 4f. The little peak at the time of 10 h is caused by the refreshing of electrolyte. After 20 h of continual electrolysis, the current density only exhibits a small drop from the peak value caused by the full electrochemical activation. The result suggests the prominent stability for long-term usage. In summary, we report the synthesis and performance of the cobalt telluride materials supported by CFP as 3D integrated electrocatalysts toward HER. Because of the advanced nanostructure of combining the CoTe2 ND or CoTe NS shells with the CoTe2 NT cores on CFP, both the CoTe2 NDs/ CoTe2 NTs and CoTe NSs/CoTe2 NTs exhibit great catalytic activities. The CoTe NSs/CoTe2 NTs could deliver the current density of 100 mA cm−2 only requiring an overpotential of 230.0 mV. After cycling for 5000 cycles or 20 h continual electrolysis, only a small performance loss was observed. The superior catalytic activity toward HER of CoTe NSs/CoTe2 NTs should be attributed to the small Rct and large ECSA, which is brought by dispersing the ultrathin NSs homogeneously on the aligned CoTe2 NTs with high electrical conductivity. The synergetic effect toward catalysis of both CoTe NSs shells and CoTe2 NTs cores also contributes to the great catalytic performance. The CoTe NSs/CoTe2 NTs supported by CFP as a 3D integrated electrode shows the potentials in HER and other renewable energy applications.
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REFERENCES
(1) Vesborg, P. C. K.; Seger, B.; Chorkendorff, I. Recent Development in Hydrogen Evolution Reaction Catalysts and Their Practical Implementation. J. Phys. Chem. Lett. 2015, 6, 951−957. (2) Xie, J. F.; Xie, Y. Structural Engineering of Electrocatalysts for the Hydrogen Evolution Reaction: Order or Disorder? ChemCatChem 2015, 7, 2568−2580. (3) Zou, X. X.; Zhang, Y. Noble Metal-Free Hydrogen Evolution Catalysts for Water Splitting. Chem. Soc. Rev. 2015, 44, 5148−5180. (4) Faber, M. S.; Jin, S. Earth-Abundant Inorganic Electrocatalysts and Their Nanostructures for Energy Conversion Applications. Energy Environ. Sci. 2014, 7, 3519−3542. (5) Zheng, Y.; Jiao, Y.; Jaroniec, M.; Qiao, S. Z. Advancing the Electrochemistry of the Hydrogen-Evolution Reaction through Combining Experiment and Theory. Angew. Chem., Int. Ed. 2015, 54, 52−65. (6) Fan, X. J.; Peng, Z. W.; Ye, R. Q.; Zhou, H. Q.; Guo, X. M3C (M: Fe, Co, Ni) Nanocrystals Encased in Graphene Nanoribbons: An Active and Stable Bifunctional Electrocatalyst for Oxygen Reduction and Hydrogen Evolution Reactions. ACS Nano 2015, 9, 7407−7418. (7) Chen, S.; Duan, J. J.; Tang, Y. H.; Jin, B.; Qiao, S. Z. Molybdenum Sulfide Clusters-Nitrogen-Doped Graphene Hybrid Hydrogel Film as An Efficient Three-dimensional Hydrogen Evolution Electrocatalyst. Nano Energy 2015, 11, 11−18. (8) Wang, K.; Zhou, C. J.; Xi, D.; Shi, Z. Q.; He, C.; Xia, H. Y.; Liu, G. W.; Qiao, G. J. Component-Controllable Synthesis of Co(SxSe1−x)2 Nanowires Supported by Carbon Fiber Paper as High-Performance Electrode for Hydrogen Evolution Reaction. Nano Energy 2015, 18, 1−11. (9) Xie, Y.; Li, B.; Su, H. L.; Liu, X. M.; Qian, Y. T. Solvothermal Route to CoTe2 Nanorods. Nanostruct. Mater. 1999, 11, 539−544. (10) Fan, H.; Zhang, Y. G.; Zhang, M. F.; Wang, X. Y.; Qian, Y. T. Glucose-Assisted Synthesis of CoTe Nanotubes in situ Templated by Te Nanorods. Cryst. Growth Des. 2008, 8, 2838−2841. (11) Jiang, L.; Zhu, Y. J.; Cui, J. B. Nanostructures of Metal Tellurides (PbTe, CdTe, CoTe2, Bi2Te3, and Cu7Te4) with Various Morphologies: A General Solvothermal Synthesis and Optical Properties. Eur. J. Inorg. Chem. 2010, 2010, 3005−3011. (12) Shi, R. R.; Liu, X. H.; Shi, Y. G.; Ma, R. Z.; Jia, B. P.; Zhang, H. T.; Qiu, G. Z. Selective Synthesis and Magnetic Properties of Uniform CoTe and CoTe2 Nanotubes. J. Mater. Chem. 2010, 20, 7634−7636. (13) Wu, G.; Cui, G. F.; Li, D. Y.; Shen, P. K.; Li, N. CarbonSupported Co1.67Te2 Nanoparticles as Electrocatalysts for Oxygen Reduction Reaction in Alkaline Electrolyte. J. Mater. Chem. 2009, 19, 6581−6589. (14) Patil, S. A.; Kim, E. K.; Shrestha, N. K.; Chang, J.; Lee, J. K.; Han, S. H. Formation of Semimetallic Cobalt Telluride Nanotube Film via Anion Exchange Tellurization Strategy in Aqueous Solution for Electrocatalytic Applications. ACS Appl. Mater. Interfaces 2015, 7, 25914−25922. (15) Khan, M. S.; Ashiq, M. N.; Ehsan, M. F.; He, T.; Ijaz, S. Controlled Synthesis of Cobalt Telluride Superstructures for the Visible Light Photo-Conversion of Carbon Dioxide into Methane. Appl. Catal., A 2014, 487, 202−209. (16) Guo, J. H.; Shi, Y. T.; Chu, Y. T.; Ma, T. L. Highly Efficient Telluride Electrocatalysts for Use as Pt-Free Counter Electrodes in Dye-Sensitized Solar Cells. Chem. Commun. 2013, 49, 10157−10159. (17) Wang, K.; Xi, D.; Zhou, C. J.; Shi, Z. Q.; Xia, H. Y.; Liu, G. W.; Qiao, G. J. CoSe2 Necklace-Like Nanowires Supported by Carbon Fiber Paper: A 3D Integrated Electrode for the Hydrogen Evolution Reaction. J. Mater. Chem. A 2015, 3, 9415−9420. (18) Kong, D. S.; Wang, H. T.; Lu, Z. Y.; Cui, Y. CoSe 2 Nanoparticles Grown on Carbon Fiber Paper: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2014, 136, 4897−4900. (19) Liang, H. F.; Li, L. S.; Meng, F.; Dang, L. N.; Zhuo, J. Q.; Forticaux, A.; Wang, Z. C.; Jin, S. Porous Two-Dimensional Nanosheets Converted from Layered Double Hydroxides and Their
ASSOCIATED CONTENT
S Supporting Information *
The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.5b10835. Experimental details, iR-correction details, additional XRD patterns, SEM, TEM images, EDS line-scan analyses, EDS spectra, equivalent circuit, and CV curves (PDF)
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AUTHOR INFORMATION
Corresponding Authors
*E-mail:
[email protected]. *E-mail:
[email protected]. Notes
The authors declare no competing financial interest.
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ACKNOWLEDGMENTS This work was supported by the National Natural Science Foundation of China (51002115, 51572111), the Innovation/ Entrepreneurship Program of Jiangsu Province (Suzutong [2013] 477 and Surencaiban [2015] 26), the Fundamental Research Funds for the Central University (XJJ2015104), the Natural Science Foundation of Jiangxi Province (20151BAB206017), and Aeronautical Science Foundation of China (2013ZF56022). 2915
DOI: 10.1021/acsami.5b10835 ACS Appl. Mater. Interfaces 2016, 8, 2910−2916
Letter
ACS Applied Materials & Interfaces Applications in Electrocatalytic Water Splitting. Chem. Mater. 2015, 27, 5702−5711. (20) Caban-Acevedo, M.; Stone, M. L.; Schmidt, J. R.; Thomas, J. G.; Ding, Q.; Chang, H. C.; Tsai, M. L.; He, J. H.; Jin, S. Efficient Hydrogen Evolution Catalysis Using Ternary Pyrite-Type Cobalt Phosphosulphide. Nat. Mater. 2015, 14, 1245−1251. (21) Zhang, H. X.; Yang, B.; Wu, X. L.; Li, Z. J.; Lei, L. C.; Zhang, X. W. Polymorphic CoSe2 with Mixed Orthorhombic and Cubic Phases for Highly Efficient Hydrogen Evolution Reaction. ACS Appl. Mater. Interfaces 2015, 7, 1772−1779. (22) Faber, M. S.; Dziedzic, R.; Lukowski, M. A.; Kaiser, N. S.; Ding, Q.; Jin, S. High-Performance Electrocatalysis Using Metallic Cobalt Pyrite (CoS2) Micro- and Nanostructures. J. Am. Chem. Soc. 2014, 136, 10053−10061. (23) Faber, M. S.; Lukowski, M. A.; Ding, Q.; Kaiser, N. S.; Jin, S. Earth-Abundant Metal Pyrites (FeS, CoS, NiS, and Their Alloys) for Highly Efficient Hydrogen Evolution and Polysulfide Reduction Electrocatalysis. J. Phys. Chem. C 2014, 118, 21347−21356. (24) Zhuo, J. Q.; Cabán-Acevedo, M.; Liang, H. F.; Samad, L.; Ding, Q.; Fu, Y. P.; Li, M. X.; Jin, S. High-Performance Electrocatalysis for Hydrogen Evolution Reaction Using Se-Doped Pyrite-Phase Nickel Diphosphide Nanostructures. ACS Catal. 2015, 5, 6355−6361. (25) Zhao, W. W.; Zhang, C.; Geng, F. Y.; Zhuo, S. F.; Zhang, B. Nanoporous Hollow Transition Metal Chalcogenide Nanosheets Synthesized via the Anion-Exchange Reaction of Metal Hydroxides with Chalcogenide Ions. ACS Nano 2014, 8, 10909−10919. (26) Beberwyck, B. J.; Surendranath, Y.; Alivisatos, A. P. Cation Exchange: A Versatile Tool for Nanomaterials Synthesis. J. Phys. Chem. C 2013, 117, 19759−19770. (27) Yin, Y. D.; Rioux, R. M.; Erdonmez, C. K.; Hughes, S.; Somorjai, G. A.; Alivisatos, A. P. Formation of Hollow Nanocrystals Through the Nanoscale Kirkendall Effect. Science 2004, 304, 711−714. (28) Liu, Y. D.; Goebl, J.; Yin, Y. D. Templated Synthesis of Nanostructured Materials. Chem. Soc. Rev. 2013, 42, 2610−2653. (29) Yang, X. L.; Lu, A. Y.; Zhu, Y. H.; Hedhili, M. N.; Min, S. X.; Huang, K. W.; Han, Y.; Li, L. J. CoP Nanosheet Assembly Grown on Carbon Cloth: A Highly Efficient Electrocatalyst for Hydrogen Generation. Nano Energy 2015, 15, 634−641. (30) Kibsgaard, J.; Tsai, C.; Chan, K.; Benck, J. D.; Norskov, J. K.; Abild-Pedersen, F.; Jaramillo, T. F. Designing an Improved Transition Metal Phosphide Catalyst for Hydrogen Evolution using Experimental and Theoretical Trends. Energy Environ. Sci. 2015, 8, 3022−3029.
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DOI: 10.1021/acsami.5b10835 ACS Appl. Mater. Interfaces 2016, 8, 2910−2916
