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Self-Template Synthesis of Co-Se-S-O Hierarchical Nanotubes as Efficient Electrocatalysts for Oxygen Evolution under Alkaline and Neutral Conditions Zhi-Mei Luo, Jia-Wei Wang, Jing-Bo Tan, Zhi-Ming Zhang, and Tong-Bu Lu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b00986 • Publication Date (Web): 13 Feb 2018 Downloaded from http://pubs.acs.org on February 13, 2018

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ACS Applied Materials & Interfaces

Self-Template Synthesis of Co-Se-S-O Hierarchical Nanotubes as Efficient Electrocatalysts for Oxygen Evolution under Alkaline and Neutral Conditions Zhi-Mei Luo,†,§ Jia-Wei Wang,†,§ Jing-Bo Tan,† Zhi-Ming Zhang,*,‡ and Tong-Bu Lu*,†,‡ †

MOE Key Laboratory of Bioinorganic and Synthetic Chemistry, School of Chemistry, Sun Yat-

Sen University, Guangzhou 510275, People’s Republic of China. ‡

Institute for New Energy Materials and Low Carbon Technologies, School of Materials Science

and Engineering, Tianjin University of Technology, Tianjin 300384, People’s Republic of China.

* To whom correspondence should be addressed. E-mail: [email protected]; [email protected].

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ABSTRACT We develop a facile self-template synthetic method to construct hierarchical CoSe-S-O (CoSexS2-x@Co(OH)2) nanotubes on a carbon cloth as a self-standing electrode for electrocatalytic oxygen-evolution reaction (OER). In the synthetic process, the separate selenization and sulfurization on Co(OH)F precursor in different solvents has played an important role in constructing CoSexS2-x (Co-Se-S) hierarchical nanotubes, which was further transformed into the nanotube-like Co-Se-S-O via an in situ electrochemical oxidation process. The Co-Se-S-O obtained by the Kirkendall effect through two stepwise anion-exchange reactions, represents the first quaternary Co-Se-S-O nanotube array, which dramatically enhances its surface area and conductivity. Further, it only requires low overpotentials of 230 and 480 mV to achieve 10 mA cm-2 current density, respectively. The OER performance of CoSe-S-O is much more efficient than that of its mono chalcogenide counterparts, as well as the commercial benchmark catalyst IrO2.

KEYWORDS nanotube, oxygen evolution reaction, self-template, Kirkendall effect, neutral condition


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INTRODUCTION Global energy crisis and environmental problems caused by consumption of fossil fuels remain as major issues.1-3 Hydrogen has been considered as a promising alternative to replace fossil fuel, which can be sustainably produced by electrochemical water splitting.4-9 During this process, the oxygen-evolution reaction (OER) at the anode seriously limits the water-splitting performance, as it demands accumulating four electrons in the OER and high activation energy barrier during O-O bond formation.10-12 Hence, efficient electrocatalysts are needed to drive the OER in an optimal potential range with a high current density.13-15 Precious metal oxides (RuO2 and IrO2) are the benchmark electrocatalysts for the OER, but their scarcity and poor durability hinder their widespread uses.12,16 Thus, it is of great significance to develop efficient OER catalysts with earth-abundant elements for large-scale application.17-22 Additionally, most OER electrocatalysts presently operate under strongly alkaline conditions (pH ≥ 13); this severely restricts the types of electrode and cell components, as well as the coupling with hydrogen-evolution reaction (HER) catalysts those are usually used in the acidic or neutral media. Also, it can effectively avoid the corrosion of the electrochemical setups by operating at neutral conditions.23 Therefore, the exploration of cost-effective OER electrocatalysts operating under the mild and neutral conditions is of great interest.23-24 Up to now, transition metal dichalcogenides (TMDs), consisting of different transition metals (Fe, Co, Ni, Mo, W, etc.) and chalcogens (S, Se, and Te) have attracted more and more attention. They are emerging as versatile materials with various applications,25-26 such as batteries, transistors and catalysis, on the basis of their structural and componential diversity,27 unique physical and chemical properties.28-32 In terms of electrocatalysts, their catalytic performances are influenced by the structures and doping elements. Hollow structures, such as nano-boxes33-34


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and nanotubes (NTs) with high surface area,21,35 are advantageous in the construction of efficient TMD-based electrocatalysts, due to their effective diffusion of substrate molecules, fast electron transfer and increased active sites. For the synthesis of hollow nanostructure, sacrificial template method has been extensively employed as an efficient strategy for constructing hollow materials.36-38 However, it usually undergoes a complex process to remove the template, and forms closed-ended structures.17,39 In contrast to the closed-ended hollow materials, the openended structures, especially for NTs, can further improve the mass diffusion and contact surface between catalyst and substrate, enabling better electrocatalytic performance.38,40-41 On the other side, the surface of TMDs tends to be oxidized to form the heterostructure,42 which is not only capable to accelerate electron transfer and increase catalytic active sites, but also can prevent further destructive oxidation of TMDs to improve their stability.43-46

Figure 1. Schematic illustrations of (a) the synthetic process of Co-Se-S-O NTs, and (b) the Kirkendall effect during the transformation from Co(OH)F to Co-Se-S NTs.


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Herein, a convenient self-template strategy to prepare hollow nanostructures without templates,32,38,47 was explored in the synthesis of the open-ended Co-Se-S-O NTs. The obtained material can be utilized as a high-performance electrocatalyst for the OER, achieving a stable 10 mA cm-2 current density for 24 h at overpotentials of 230 mV (pH 13.6) and 480 mV (pH 7.0), respectively.

RESULTS AND DISCUSSION Synthesis and Characterization. The synthetic process of Co-Se-S-O is displayed in Figure 1a, where the morphological changes were monitored by scanning electron microscope (SEM) and transmission electron microscope (TEM, Figure S1). The synthesis began with a direct growth of Co(OH)F nanowires (NWs) on CC, which were converted into Co-Se-S NTs via two stepwise anion-exchange reactions, where the OH- and F- anions in Co(OH)F were replaced by the in-situ generated Se2- and S2-, respectively. Notably, different from other methods,48-49 doping different chalcogens into Co(OH)F by separate selenization and sulfurization in different solvents represents a key factor in constructing the ternary Co-Se-S hierarchical NTs. In the selenization process, absolute alcohol was selected as the solvent to prevent significant consumption of NaBH4 by water, which facilitated the reaction between NaBH4 and Se powder to readily form NaHSe,50 the real reagent for selenization reaction. Subsequently, deionized water was utilized as the solvent in the sulfurization process to provide more protons that could react with thiourea to form H2S. This two-step method represents a new and efficient way for constructing ternary hollow TMDs. In this way, Co(OH)F, Co-Se and Co-Se-S samples were prepared in turn (Figure 1b). SEM and TEM images (Figure. S1) show that Co(OH)F and Co-Se samples are comprised of


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vertically aligned NWs with average length of 5 µm and a diameter of ca. 100 nm. After sulfurization reaction, the resulting Co-Se-S sample contains hollow NTs that inherit the diameter (approximately 100 nm) of the precursors with a thickness of approximately 10-20 nm. These observations demonstrate that the Co-Se NWs were converted to the Co-Se-S NTs after the sulfurization reaction, which can be ascribed to the Kirkendall effect during the anionexchange process.38,47 In the selenization and sulfurization of Co(OH)F NWs, the OH- and F- are replaced by Se2- and S2-, and the Co2+ diffuses outward simultaneously, resulting in the Co-Se-S NTs. Notably, self-template formation of NTs on a conductive substrate would offer extra advantages, including easy synthesis, excellent mechanical adhesion, convenient mass diffusion and suppressing the blockage of active sites.17,39,51 Also, it could be found that the Co-S and CoSe samples prepared through single anion-exchange reaction, either selenization or sulfurization, were comprised of NWs (for Co-Se) or nano-rods (for Co-S) rather than hollow NTs (Figure S2). Finally, a uniform surface oxidation of Co-Se-S was achieved by controlled-current electrolysis (CCE), affording the final Co-Se-S-O NTs. As shown in Figure 2 and S3, the as-prepared Co-SeS-O NTs inherited the NT-like morphology of Co-Se-S with more wrinkled surfaces that are presumably to be Co(OH)2 layers.49 Meanwhile, the mono chalcogenide counterparts, Co-Se-O and Co-S-O, were also prepared by electrochemical oxidation on Co-Se and Co-S samples, respectively (Figure S4). High-resolution TEM (HRTEM) images show that the crystal lattice spacings in the center of Co-Se-S-O NTs are 0.243 and 0.210 nm (Figure 2d), which are between those of CoSe2 (0.241 and 0.209 nm) and CoS2 (0.255 and 0.221 nm), respectively, towards [220] and [211] crystal orientations, due to the introduction of S atoms into the CoSe2 phase. These results are also supported by the powder X-ray diffraction (PXRD; Figure S6) analysis. In addition, it can be


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noticed that the crystal lattice spacings close to the edge of NTs are 0.282 and 0.212 nm, which correspond to [012] and [011] crystal orientations of Co(OH)2, respectively. As compared with the PXRD patterns of CoS2 (PDF# 89-1492), CoSe2 (PDF# 88-1712) and Co(OH)2 (PF#741057), it can be concluded that the dominant components of Co-Se-S and Co-Se-S-O should be CoSexS2-x and CoSexS2-x-Co(OH)2, respectively. Overall, the above findings confirm that the hierarchical Co-Se-S-O NT consists of the CoSexS2-x@Co(OH)2 heterostructure.

Figure 2. (a) (b) SEM, (c) TEM and (d) HRTEM images of Co-Se-S-O NTs; XPS spectra of (e) Co 2p, (f) S 2p, (g) Se 2p and (h) O 1s region for Co-Se-S and Co-Se-S-O samples; (i) EDX elemental mapping of Co-Se-S-O.


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Further, an inductively coupled plasma atomic emission spectroscopy (ICP-AES, Table S1) was performed to determine the chemical composition of the bulk Co-Se-S and Co-Se-S-O samples. The ICP-AES results of Co-Se-S show that the elements of Co, S and Se exist in the asprepared ternary TMD, and the ratios of Se : S and Co : (Se + S) are approximately 1:5 and 1:2, respectively. Accordingly, the chemical formula of Co-Se-S was determined to be CoSexS2-x (x ≈ 0.33). The results of energy dispersive X-ray spectroscopy (EDS) also confirm the existence of Co, S and Se in both the samples of Co-Se-S and Co-Se-S-O (Figure S5). Additionally, the results of ICP-AES indicate that the atom ratio of Se and S significantly decreased after electrochemical oxidation, indicating the oxidative transformation from Co-Se-S to Co-Se-S-O. In addition, the chemical composition on the surfaces of Co-Se-S and Co-Se-S-O NTs was further determined by X-ray photoelectron spectroscopy (XPS). For Co-Se-S, the binding energies of Co 2p at 778.5, 780.5 and 784.4 eV correspond to metallic Co, Co 2p3/2 and Co 2p1/2, respectively (Figure 2e), consistent with the presence of Coξ+ (0 < ξ < 2) cations.52-53 Importantly, the binding energies of S 2p in the range of 162-165 eV (Figure 2f) and Se 3d (Figure 2g) at 54.6 and 55.5 eV suggest the presence of Co-S54 and Co-Se55-56 bonds. These results indicate the formation of pyrite-type Co sulphide/selenide in Co-Se-S sample.48-49,57 The binding energy of O 1s at 532.2 eV reveals the presence of O from surface-absorbed H2O (Figure 2h).58 On the other hand, compared to Co-Se-S, the XPS pattern of Co-Se-S-O demonstrates the successful oxidation on the surface of Co-Se-S according to the following observations: (1) the positive shifts of the binding energies of Co; (2) the disappearance of the binding energies responsible for Co-S (Figure 2f) and Co-Se species (Figure 2g);49,57 (3) the enhancement of the binding energy corresponding to SeOx species (at 59.7 eV, Figure 2g);59 (4) the appearance of binding energies of O 1s at 531.0 and 529.4 eV for cobalt hydroxides and oxides, respectively


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(Figure 2h).58 These XPS results also confirm that the surface of pyrite-type cobalt sulphide/selenide was converted to cobalt hydroxide. Electrocatalytic OER. The electrocatalytic performance of Co-Se-S-O NTs for the OER was investigated in a typical three-electrode configuration in O2-saturated 1 M KOH electrolyte. The Co(OH)F precursor, Co-Se-O, Co-S-O, commercial IrO2 (loaded on CC) and bare CC were utilized for comparison. All initial data are presented after ohmic correction for assessing the intrinsic activity of the catalysts, and the polarization curves before and after ohmic correction for Co-Se-S-O were also supplied as Figure S7. Among them, Co-Se-S-O NTs exhibit the highest electrocatalytic activity for OER (230 mV at 10 mA cm-2), much better than those of CoS-O (270 mV) and Co-Se-O samples (280 mV, Figure 3a and S8). The polarization curves of different catalysts show that the current density of Co-Se-S-O at 1.55 V versus reversible hydrogen electrode (vs RHE) is approximately 2.5 and 12 times higher than those of Co-S-O and Co-Se-O, respectively, and dramatically surpasses that of IrO2. These results demonstrate that the doubly-doped catalyst exhibits much higher electrocatalytic activity than those of the mono chalcogenide counterparts (Co-Se-O and Co-S-O) and the commercial benchmark catalyst IrO2. Also, it could be observed that the catalytic activity of Co-S-O NWs and Co-Se-O NWs is dramatically enhanced compared to that of Co(OH)F and CC, indicating that the co-existence of Se and S in the TMD plays an important role in the enhancement of the catalytic activity. Meanwhile, a Tafel slope (Figure S7) was estimated to be 86.1 mV dec-1 in the case of Co-Se-SO NTs, which is much smaller than those of Co-S-O nano-rods (111.2 mV·dec-1) and Co-Se-O NWs (145.3 mV·dec-1). These results manifest that Co-Se-S-O NTs display more favorable kinetics for OER. All these results confirm that the Se and S co-doping represents an effective


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strategy for constructing efficient OER electrocatalysts. This catalytic activity is superior to most pioneering monometallic cobalt-based OER electrocatalysts (see Table S2). Moreover, Co-Se-S-O NTs display excellent durability, where the overpotential of 230 mV could be maintained over 24 h of CCE (Figure 3b). Also, the polarization curves before and after 24 h of CCE at 10 mA/cm2 are almost identical (Figure S8), further indicating its stability. The strong mechanical adhesion enabled by in situ growth of Co-Se-S-O NTs on CC and formation of the protective cobalt-hydroxide layer contribute to its impressive stability. The Faradaic efficiency of this catalytic system was also determined. In this process, the O2 product was quantitatively monitored by gas chromatography after 1 h of electrolysis at 10 mA cm-2. The Faradaic efficiency was estimated to be 92 ± 3%, confirming the high activity and robustness of Co-Se-S-O NTs for the OER in the alkaline aqueous solution (see SI for further details). The Faradaic efficiency was estimated to be lower than 100%, which may be attributed to the dissolution of some produced O2 in the electrolyte.


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Figure 3. (a) Polarization curves in 1.0 M KOH; (b) current density traces of CCE at 10 mA/cm2 for OER in 1.0 M KOH; (c) polarization curve for Co-Se-S-O in 0.1 M pH 7.0 PBS; (d) current density trace of CCE for Co-Se-S-O at 10 mA/cm2 for OER in 0.1 M pH 7.0 PBS; (e) linear fitting of the capacitive currents at 0.3994 V vs RHE at various scan rates in 1.0 M KOH; (f) EIS plots of Co-S-O, Co-Se-O and Co-Se-S-O. Interestingly, it was found that the Co-Se-S-O NTs also exhibit superb electrocatalytic activity for OER in pH 7.0 phosphate-buffered solution (PBS). The polarization curves (Figure 3c) show that the Co-Se-S-O NTs is highly active for OER in 0.1 M neutral PBS. Moreover, the Co-Se-SO NTs exhibit a sustained overpotential of 480 mV during 28 h of CCE at 10 mA cm-2 (Figure 3d), demonstrating its high stability under neutral conditions. Notably, this overpotential is comparable to most reported values for non-noble-metal OER catalysts in neutral systems (Table S3), such as those of α-Co2P (590 mV),60 Co-Pi NA/Ti (450 mV)39 and Ni-Fe-P (430 mV),61


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indicating that the Co-Se-S-O NTs can be promising electrocatalysts for OER at neutral conditions. To verify the origin of this high performance, the electrochemically active surface area (ECSA), and the double-layer capacitance (Cdl), were determined by cyclic voltammetry at varying scan rates (Figure 3e and S9). As shown in Figure 3e, the Cdl of Co-Se-O and Co-S-O electrodes are 0.732 mF cm-2 and 0.764 mF cm-2, respectively, whereas that of Co-Se-S-O is 1.00 mF cm-2. Based on the equation of ECSA = Cdl/Cs, where Cs is the specific capacitance of the materials (Here Cs = 0.040 mF cm-2 in 1.0 M KOH solution). Thus, Co-Se-S-O has the estimated ECSA value of 25 cm2, much larger than those of Co-Se-O (18.3 cm2) and Co-S-O (19.1 cm2). The increased ECSA of Co-Se-S-O over the other two counterparts can be attributed to its openended hollow structure and more wrinkled surface (Figure S1). Furthermore, we conducted electrochemical impedance spectroscopy (EIS) measurements on the CC electrodes with Co-Se-S-O, Co-S-O and Co-Se-O catalysts, respectively. For each sample, the impedance at high-frequency limit is defined as its ohmic resistance (Rs) and the diameter of the semicircle is its charge-transfer resistance (Rct).62 The obtained Nyquist plots (Figure 3f) exhibit that Rs of each electrode is only approximately 2.75 Ω, suggesting small Ohmic losses during the OER with these electrocatalysts. In addition, Nyquist plots displayed that Rct controls the kinetics at the electrode interface.63-64 More importantly, the Rct of Co-Se-SO NTs on CC (0.13 Ω) is significantly lower than those of Co-S-O (0.27 Ω) and Co-Se-O (0.81 Ω), revealing a faster charge transport during the OER process. On the other side, we also measured the conductance of compacted pallets of Co-Se-S-O, Co-S-O and Co-Se-O samples, giving the values of 2.33, 0.176 and 0.035 S cm–1, respectively (Figure S10). Thus, both the measurements on charge-transfer resistance and conductance reveal that the Co-Se-S-O NTs


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possess higher conductivity compared to that of Co-S-O and Co-Se-O, which are partly attributed to the co-existence of Se and S in the Co-S-Se-O composite.65 The incorporation of double charcogen elements may optimize the electronic structure and thus modulate the binding energies of O and OH species to optimal values. Moreover, the order of observed catalytic activities of these composites is consistent with their order of conductivity: Co-Se-S-O NTs > Co-S-O NRs > Co-Se-O NWs. Accordingly, it can be concluded that the incorporation of double charcogen elements in the TMD-based catalysts can efficiently improve their catalytic activity.

CONCLUSION

In summary, we have successfully explored a facile self-template method to fabricate quaternary Co-Se-S-O hierarchical NTs on CC via two stepwise anion-exchange reactions. The separate selenization and sulfurization of Co(OH)F in different solvents plays an important role in constructing the Co-Se-S hierarchical NTs. A subsequent electrochemical oxidation results in the formation of Co-Se-S-O heterostructure, achieving increased surface area and high conductivity. This material can be directly used as a cost-efficient OER electrocatalyst in both alkaline and neutral media. It only requires low overpotentials of 230 mV and 480 mV to achieve 10 mA cm-2 current density at alkaline and neutral conditions, respectively, much superior to those of mono chalcogenide counterparts, as well as the commercial benchmark catalyst IrO2. This work not only supplies a high-performance OER electrocatalyst, but also gain new insights for the growth of hollow TMD-based materials.

EXPERIMENTAL SECTION


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Materials and Methods. Co(NO3)2·6H2O (99+% for analysis, ACROS), IrO2 (99.99% metals basis, Alfa), CC (WOS1002, CeTech), Nafion (5 wt%, Sigma-Aldrich) and other materials were obtained from commercial suppliers and used without further purification, unless otherwise noted. SEM images and EDS spectra were collected by field emission scanning electron microscope (FEI, Quanta 400). ICP-AES data were obtained on an optical emission spectrometer (PerkinElmer, Optima 8300). HRTEM images and elemental mapping were taken on by JEM2100F. PXRD measurements were performed on a D8 A1DVANCE X-ray Diffractometer. XPS data was collected on an ESCA Lab250 instrument. Electrocatalytic properties were studied on a CHI760E electrochemical workstation. An Ag/AgCl (in 3 M KCl solution) electrode and a Pt wire was used as the reference electrode and counter electrode, respectively. The EIS measurements were conducted over a frequency range from 10 kHz to 100 kHz. Electrical conductivity measurements were conducted using a Keithley model 6517b electrometer under direct current using two-probe method. The analysis of gas product was operated on a gas chromatography (Agilent 7820A-GC) with a thermal conductivity detector. Synthesis of Co(OH)F/CC. The Co(OH)F NWs were grown on CC by a modified method. In detail, the CC was ultrasonically washed by acetone, ethanol and deionized water, respectively. Then, the CC was further treated in concentrated HNO3 at 100 oC for 1 h, followed by washing with deionized water. Subsequently, a mixture containing 6 mM Co(NO3)2·6H2O, 30 mM urea, 15 mM NH4F and 20 mL deionized water, was transferred into a 25 mL Teflon-lined stainless steel autoclave with two pieces of pre-treated CC (1 × 2 cm). Then the autoclave was kept in the oven and maintained at 120 oC for 6 h to obtain Co(OH) F NWs /CC. Synthesis of Co-Se/CC. 65 mg NaBH4 and 59 mg Se powder were added into a flask with gently stirring, then 30 mL absolute ethanol was added into the mixed solution under Ar flow.


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The resulting solution was transferred into a 50 mL Teflon-lined stainless steel autoclave with two pieces of Co(OH)F NWs/CC (1 × 2 cm). The autoclave was maintained at 140 oC for 10 h, and the obtained material was rinsed with ethanol and water, respectively. Synthesis of Co-Se-S/CC and Co-Se-S-O/CC. 220 mg SC(NH2)2 was dissolved in 15 mL deionized water, and then the solution was put into a 25 mL Teflon-lined stainless steel autoclave with two pieces of CoSe2 NT/CC (1 × 2 cm). The autoclave was maintained at 160 oC for 10 h, and the obtained material was rinsed with ethanol and water, respectively. Subsequently, the obtained Co-Se-S NT/CC was used as an anode to proceed CCE in 1.0 M KOH at 10 mA cm-2 for 2 h to attain the oxidized material. The loading amount of Co-Se-S-O NTs CC was determined by mass discrepancy of CC before and after the growth of NTs, which is approximately 2.0 mg/cm2. Synthesis of Co-Se-O/CC. 130 mg NaBH4 and 118 mg Se powder were added into a flask, and 30 mL absolute ethanol was added into the mixed solution under Ar flow with gently stirring. Then, the solution was transferred into a 50 mL Teflon-lined stainless steel autoclave with two pieces of Co(OH)F NWs/CC. The autoclave was maintained at 140 oC for 10 h, and the obtained material was rinsed with ethanol and water, respectively. The obtained CoSe2/CC was used as an anode in 1.0 M KOH to proceed CCE at 10 mA cm-2 for 2 h to attain the oxidized material of Co-Se-O /CC. Synthesis of Co-S-O NRs/CC. 440 mg SC(NH2)2 was dissolved in 15 mL deionized water, and then the solution was put into a 25 mL Teflon-lined stainless steel autoclave with two pieces of Co(OH)F NW/CC (1 × 2 cm). The autoclave was maintained at 160 oC for 10 h, and the obtained material was rinsed with ethanol and water, respectively. Then the Co-S NRs/CC was


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used as an anode in 1.0 M KOH to proceed CCE at 10 mA cm-2 for 2 h to synthesize Co-S-O /CC. Preparation of IrO2/CC. 10 mg of IrO2 and 50 µL of Nafion (5 wt%) were dispersed in 1 mL of ethanol with sonication for at least 30 min to generate a homogeneous ink. Then, 200 µL ink was drop-casted onto a CC (1 × 1 cm) to afford a loading mount of approximately 2.0 mg/cm2, and then the solvent was evaporated at room temperature overnight. ASSOCIATED CONTENT Supporting Information Supplementary experimental detail, additional figures and crystallographic data as noted in the text. This material is available free of charge via the Internet at http://pubs.acs.org. Author Contributions §

Z.L and J.W contribute equally to this work.

Notes The authors declare no competing financial interests. ACKNOWLEDGMENTS We are grateful for the financial support from the National Natural Science Foundation of China (21331007 and 21790052), the 973 program of China (2014CB845602), the NSF of Guangdong Province (S2012030006240). REFERENCES 1. Lewis, N. S.; Nocera, D. G. Powering the Planet: Chemical Challenges in Solar Energy Utilization. Proc. Natl. Acad. Sci. U. S. A. 2006, 103, 15729-15735.


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2. Zou, X.; Zhang, Y. Noble Metal-Free Hydrogen Evolution Catalysts for Water Splitting. Chem. Soc. Rev. 2015, 44, 5148-5180. 3. Zhang, N.; Long, R.; Gao, C.; Xiong Y. Recent progress on advanced design for photoelectrochemical reduction of CO2 to fuels. Sci China Mater 2018, doi: 10.1007/s40843017-9151-y. 4. Jiao, Y.; Zheng, Y.; Davey, K.; Qiao, S.-Z. Activity Origin and Catalyst Design Principles For electrocatalytic Hydrogen Evolution on Heteroatom-Doped Graphene. Nat. Energy 2016, 1, 16130. 5. Xu, Y.; Zhang, B. Recent Advances in Porous Pt-Based Nanostructures: Synthesis and Electrochemical Applications. Chem. Soc. Rev. 2014, 43, 2439-2450. 6. Shi, Y.; Zhang, B. Recent Advances in Transition Metal Phosphide Nanomaterials: Synthesis and Applications in Hydrogen Evolution Reaction. Chem. Soc. Rev. 2016, 45, 1529-1541. 7. Yan, H.; Tian, C.; Wang, L.; Wu, A.; Meng, M.; Zhao, L.; Fu, H. Phosphorus-Modified Tungsten Nitride/Reduced Graphene Oxide as a High-Performance, Non-Noble-Metal Electrocatalyst for the Hydrogen Evolution Reaction. Angew. Chem. Int. Ed. 2015, 54, 63256329. 8. Yan, H.; Xie, Y.; Jiao, Y.; Wu, A.; Tian, C.; Zhang, X.; Wang, L.; Fu, H. Holey Reduced Graphene Oxide Coupled with an Mo2N-Mo2C Heterojunction for Efficient Hydrogen Evolution. Adv. Mater. 2018, 30, 1704156. 9. Zhang, G.; Wang, G.; Liu, Y.; Liu, H.; Qu, J.; Li, J. Highly Active and Stable Catalysts of Phytic Acid-Derivative Transition Metal Phosphides for Full Water Splitting. J. Am. Chem. Soc. 2016, 138, 14686-14693.


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10. Chen, P.; Xu, K.; Zhou, T.; Tong, Y.; Wu, J.; Cheng, H.; Lu, X.; Ding, H.; Wu, C.; Xie, Y. Strong-Coupled Cobalt Borate Nanosheets/Graphene Hybrid as Electrocatalyst for Water Oxidation under Both Alkaline and Neutral Conditions. Angew. Chem. Int. Ed. 2016, 55, 24882492. 11. Sun, J.; Yin, H.; Liu, P.; Wang, Y.; Yao, X.; Tang, Z.; Zhao, H. Molecular Engineering of Ni-/Co-Porphyrin Multilayers on Reduced Graphene Oxide Sheets as Bifunctional Catalysts for Oxygen Evolution and Oxygen Reduction Reactions. Chem. Sci. 2016, 7, 5640-5646. 12. Dou, S.; Dong, C.-L.; Hu, Z.; Huang, Y.-C.; Chen, J.-l.; Tao, L.; Yan, D.; Chen, D.; Shen, S.; Chou, S.; Wang, S. Atomic-Scale CoOx Species in Metal-Organic Frameworks for Oxygen Evolution Reaction. Adv. Funct. Mater. 2017, 27, 1702546. 13. Tan, J.-B.; Sahoo, P.; Wang, J.-W.; Hu, Y.-W.; Zhang, Z.-M.; Lu, T.-B. Highly Efficient Oxygen Evolution Electrocatalysts Prepared by Using Reduction-Engraved Ferrites on Graphene Oxide. Inorg. Chem. Front. 2018, DOI: 10.1039/c7qi00681k. 14. Liu, Y.; Li, Q.; Si, R.; Li, G. D.; Li, W.; Liu, D. P.; Wang, D.; Sun, L.; Zhang, Y.; Zou, X. Coupling Sub-Nanometric Copper Clusters with Quasi-Amorphous Cobalt Sulfide Yields Efficient and Robust Electrocatalysts for Water Splitting Reaction. Adv. Mater. 2017, 29, 1606200. 15. Zhang, F.-S.; Wang, J.-W.; Luo, J.; Liu, R.-R.; Zhang, Z.-M.; He, C.-T.; Lu, T.-B. Extraction of Nickel from NiFe-LDH into Ni2P@NiFe Hydroxide as a Bifunctional Electrocatalyst for Efficient Overall Water Splitting. Chem. Sci. 2018, 9, 1375-1384. 16. Wang, P.; Zhang, X.; Zhang, J.; Wan, S.; Guo, S.; Lu, G.; Yao, J.; Huang, X. Precise Tuning in Platinum-Nickel/Nickel Sulfide Interface Nanowires for Synergistic Hydrogen Evolution Catalysis. Nat. Commun. 2017, 8, 14580.


18

Page 19 of 26 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


17. Zhu, Y. P.; Ma, T. Y.; Jaroniec, M.; Qiao, S. Z. Self-Templating Synthesis of Hollow Co3O4 Microtube Arrays for Highly Efficient Water Electrolysis. Angew. Chem. Int. Ed. 2017, 56, 1324-1328. 18. Xiao, Z.; Wang, Y.; Huang, Y.-C.; Wei, Z.; Dong, C.-L.; Ma, J.; Shen, S.; Li, Y.; Wang, S. Filling the Oxygen Vacancies in Co3O4 with Phosphorus: An Ultra-Efficient Electrocatalyst for Overall Water Splitting. Energy Environ. Sci. 2017, 10, 2563-2569. 19. Zhuang, L.; Ge, L.; Yang, Y.; Li, M.; Jia, Y.; Yao, X.; Zhu, Z. Ultrathin Iron-Cobalt Oxide Nanosheets with Abundant Oxygen Vacancies for the Oxygen Evolution Reaction. Adv. Mater. 2017, 29, 1606793. 20. Chen, D.; Dong, C. L.; Zou, Y.; Su, D.; Huang, Y. C.; Tao, L.; Dou, S.; Shen, S.; Wang, S. In Situ Evolution of Highly Dispersed Amorphous CoOx Clusters for Oxygen Evolution Reaction. Nanoscale 2017, 9, 11969-11975. 21. Liu, H.; Li, H.; Wang, X. Electrostatic Interaction-Directed Growth of Nickel Phosphate Single-Walled Nanotubes for High Performance Oxygen Evolution Reaction Catalysts. Small 2016, 12, 2969-2974. 22. Sun, M.; Liu, H.; Qu, J.; Li, J. Earth-Rich Transition Metal Phosphide for Energy Conversion and Storage. Adv. Energy Mater. 2016, 6, 1600087. 23. Wu, J.; Xue, Y.; Yan, X.; Yan, W.; Cheng, Q.; Xie, Y. Co3O4 Nanocrystals on Single-Walled Carbon Nanotubes as a Highly Efficient Oxygen-Evolving Catalyst. Nano Res. 2012, 5, 521-530. 24. Kudo, A.; Miseki, Y. Heterogeneous Photocatalyst Materials for Water Splitting. Chem. Soc. Rev. 2009, 38, 253-278. 25. Ping, J.; Wang, Y.; Lu, Q.; Chen, B.; Chen, J.; Huang, Y.; Ma, Q.; Tan, C.; Yang, J.; Cao, X.; Wang, Z.; Wu, J.; Ying, Y.; Zhang, H. Self-Assembly of Single-Layer CoAl-Layered Double


19


Page 20 of 26

Hydroxide Nanosheets on 3D Graphene Network Used as Highly Efficient Electrocatalyst for Oxygen Evolution Reaction. Adv. Mater. 2016, 28, 7640-7645. 26. Huang, X.; Zeng, Z.; Bao, S.; Wang, M.; Qi, X.; Fan, Z.; Zhang, H. Solution-Phase Epitaxial Growth of Noble Metal Nanostructures on Dispersible Single-Layer Molybdenum Disulfide Nanosheets. Nat. Commun. 2013, 4, 1444. 27. Liu, R.; Wang, Y.; Liu, D.; Zou, Y.; Wang, S. Water-Plasma-Enabled Exfoliation of Ultrathin Layered Double Hydroxide Nanosheets with Multivacancies for Water Oxidation. Adv. Mater. 2017, 29, 1701546. 28. Podzorov, V.; Gershenson, M. E.; Kloc, C.; Zeis, R.; Bucher, E. High-Mobility Field-Effect Transistors Based on Transition Metal Dichalcogenides. Appl. Phys. Lett. 2004, 84, 3301-3303. 29. Stephenson, T.; Li, Z.; Olsen, B.; Mitlin, D. Lithium Ion Battery Applications of Molybdenum Disulfide (MoS2) Nanocomposites. Energy Environ. Sci. 2014, 7, 209-231. 30. Tan, C.; Zhang, H. Two-Dimensional Transition Metal Dichalcogenide Nanosheet-Based Composites. Chem. Soc. Rev. 2015, 44, 2713-2731. 31. Wang, Q. H.; Kalantar-Zadeh, K.; Kis, A.; Coleman, J. N.; Strano, M. S. Electronics and Optoelectronics of Two-Dimensional Transition Metal Dichalcogenides. Nat. Nanotechnol. 2012, 7, 699-712. 32. Zhao, W.; Zhang, C.; Geng, F.; Zhuo, S.; 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. 33. Yu, L.; Xia, B. Y.; Wang, X.; Lou, X. W. General Formation of M-MoS3 (M = Co, Ni) Hollow Structures with Enhanced Electrocatalytic Activity for Hydrogen Evolution. Adv. Mater. 2016, 28, 92-97.


20

Page 21 of 26 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


34. Yu, X. Y.; Feng, Y.; Jeon, Y.; Guan, B.; Lou, X. W.; Paik, U. Formation of Ni-Co-MoS2 Nanoboxes with Enhanced Electrocatalytic Activity for Hydrogen Evolution. Adv. Mater. 2016, 28, 9006-9011. 35. Zhang, K.; Lin, Y.; Muhammad, Z.; Wu, C.; Yang, S.; He, Q.; Zheng, X.; Chen, S.; Ge, B.; Song, L. Active {010} Facet-Exposed Cu2MoS4 Nanotube as High-Efficiency Photocatalyst. Nano Res. 2017, 10, 3817-3825. 36. Cai, G.; Zhang, W.; Jiao, L.; Yu, S.-H.; Jiang, H.-L. Template-Directed Growth of WellAligned MOF Arrays and Derived Self-Supporting Electrodes for Water Splitting. Chem 2017, 2, 791-802. 37. Fang, X.; Jiao, L.; Zhang, R.; Jiang, H.-L. Porphyrinic Metal-Organic Framework-Templated Fe-Ni-P/Reduced Graphene Oxide for Efficient Electrocatalytic Oxygen Evolution. ACS Appl. Mater. Interfaces 2017, 9, 23852-23858. 38. Wang, H.; Zhuo, S.; Liang, Y.; Han, X.; Zhang, B. General Self-Template Synthesis of Transition-Metal

Oxide

and

Chalcogenide

Mesoporous

Nanotubes

with

Enhanced

Electrochemical Performances. Angew. Chem. Int. Ed. 2016, 55, 9055-9059. 39. Xie, L.; Zhang, R.; Cui, L.; Liu, D.; Hao, S.; Ma, Y.; Du, G.; Asiri, A. M.; Sun, X. HighPerformance Electrolytic Oxygen Evolution in Neutral Media Catalyzed by a Cobalt Phosphate Nanoarray. Angew. Chem. Int. Ed. 2017, 56, 1064-1068. 40. Yu, L.; Zhang, L.; Wu, H. B.; Lou, X. W. Formation of NixCo3-xS4 Hollow Nanoprisms with Enhanced Pseudocapacitive Properties. Angew. Chem. Int. Ed. 2014, 53, 3711-3714. 41. Guan, C.; Liu, X.; Elshahawy, A. M.; Zhang, H.; Wu, H.; Pennycook, S. J.; Wang, J. MetalOrganic Framework Derived Hollow CoS2 Nanotube Arrays: An Efficient Bifunctional Electrocatalyst for Overall Water Splitting. Nanoscale Horiz. 2017, 2, 342-348.


21


Page 22 of 26

42. Han, L.; Meng, Q.; Wang, D.; Zhu, Y.; Wang, J.; Du, X.; Stach, E. A.; Xin, H. L. Interrogation of Bimetallic Particle Oxidation in Three Dimensions at the Nanoscale. Nat. Commun. 2016, 7, 13335. 43. Ding, Q.; Meng, F.; English, C. R.; Caban-Acevedo, M.; Shearer, M. J.; Liang, D.; Daniel, A. S.; Hamers, R. J.; Jin, S. Efficient Photoelectrochemical Hydrogen Generation Using Heterostructures of Si and Chemically Exfoliated Metallic MoS2. J. Am. Chem. Soc. 2014, 136, 8504-8507. 44. Lukowski, M. A.; Daniel, A. S.; Meng, F.; Forticaux, A.; Li, L.; Jin, S. Enhanced Hydrogen Evolution Catalysis from Chemically Exfoliated Metallic MoS2 Nanosheets. J. Am. Chem. Soc. 2013, 135, 10274-10277. 45. Zhou, W.; Wu, X.-J.; Cao, X.; Huang, X.; Tan, C.; Tian, J.; Liu, H.; Wang, J.; Zhang, H. Ni3S2 Nanorods/Ni Foam Composite Electrode with Low Overpotential for Electrocatalytic Oxygen Evolution. Energy Environ. Sci. 2013, 6, 2921-2924. 46. Wu, Y. Y.; Li, G. D.; Liu, Y. P.; Yang, L.; Lian, X. R.; Asefa, T.; Zou, X. X. Overall Water Splitting Catalyzed Efficiently by an Ultrathin Nanosheet-Built, Hollow Ni3S2-Based Electrocatalyst. Adv. Funct. Mater. 2016, 26, 4839-4847. 47. Wang, W.; Ren, X.; Hao, S.; Liu, Z.; Xie, F.; Yao, Y.; Asiri, A. M.; Chen, L.; Sun, X. SelfTemplating Construction of Hollow Amorphous CoMoS4 Nanotube Array Towards Efficient Hydrogen Evolution Electrocatalysis at Neutral pH. Chem. - Eur. J. 2017, 23, 12718-12723. 48. Fang, L.; Li, W.; Guan, Y.; Feng, Y.; Zhang, H.; Wang, S.; Wang, Y. Tuning Unique Peapod-Like Co(SxSe1-x)2 Nanoparticles for Efficient Overall Water Splitting. Adv. Funct. Mater. 2017, 27, 1701008.


22

Page 23 of 26 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


49. Liu, K.; Wang, F.; Xu, K.; Shifa, T. A.; Cheng, Z.; Zhan, X.; He, J. CoS2xSe2(1-x) Nanowire Array: An Efficient Ternary Electrocatalyst for the Hydrogen Evolution Reaction. Nanoscale 2016, 8, 4699-4704. 50. L, D.; Klayman; Griffin, T. S. Reaction of Selenium with Sodium Borohydride in Protic Solvents. A Facile Method for the Introduction of Selenium into Organic Molecules. J. Am. Chem. Soc. 1973, 197-199. 51. Jiang, P.; Liu, Q.; Liang, Y.; Tian, J.; Asiri, A. M.; Sun, X. A Cost-Effective 3D Hydrogen Evolution Cathode with High Catalytic Activity: FeP Nanowire Array as the Active Phase. Angew. Chem. Int. Ed. 2014, 53, 12855-12859. 52. Jiang, N.; You, B.; Sheng, M.; Sun, Y. Electrodeposited Cobalt-Phosphorous-Derived Films as Competent Bifunctional Catalysts for Overall Water Splitting. Angew. Chem. Int. Ed. 2015, 54, 6251-6254. 53. Jiao, L.; Zhou, Y.-X.; Jiang, H.-L. Metal-Organic Framework-Based CoP/Reduced Graphene Oxide: High-Performance Bifunctional Electrocatalyst for Overall Water Splitting. Chem. Sci. 2016, 7, 1690-1695. 54. Cai, P.; Huang, J.; Chen, J.; Wen, Z. Oxygen-Containing Amorphous Cobalt Sulfide Porous Nanocubes as High-Activity Electrocatalysts for the Oxygen Evolution Reaction in an Alkaline/Neutral Medium. Angew. Chem. Int. Ed. 2017, 56, 4858-4861. 55. Kong, D.; Wang, H.; Lu, Z.; Cui, Y. CoSe2 Nanoparticles Grown on Carbon Fiber Paper: An Efficient and Stable Electrocatalyst for Hydrogen Evolution Reaction. J. Am. Chem. Soc. 2014, 136, 4897-4900.


23


Page 24 of 26

56. Liu, K.; Wang, F.; Shifa, T. A.; Wang, Z.; Xu, K.; Zhang, Y.; Cheng, Z.; Zhan, X.; He, J. An Efficient Ternary CoP2xSe2(1-x) Nanowire Array for Overall Water Splitting. Nanoscale 2017, 9, 3995-4001. 57. Wang, K.; Zhou, C.; Xi, D.; Shi, Z.; He, C.; Xia, H.; Liu, G.; Qiao, G. ComponentControllable Synthesis of Co(SxSe1-x)2 Nanowires Supported by Carbon Fiber Paper as HighPerformance Electrode for Hydrogen Evolution Reaction. Nano Energy 2015, 18, 1-11. 58. Zhang, C.; Xiao, J.; Lv, X.; Qian, L.; Yuan, S.; Wang, S.; Lei, P. Hierarchically Porous Co3O4/C Nanowire Arrays Derived from a Metal-Organic Framework for High Performance Supercapacitors and the Oxygen Evolution Reaction. J. Mater. Chem. A 2016, 4, 16516-16523. 59. Chen, W.; Liu, Y.; Li, Y.; Sun, J.; Qiu, Y.; Liu, C.; Zhou, G.; Cui, Y. In Situ Electrochemically Derived Nanoporous Oxides from Transition Metal Dichalcogenides for Active Oxygen Evolution Catalysts. Nano Lett. 2016, 16, 7588-7596. 60. Xu, K.; Cheng, H.; Liu, L.; Lv, H.; Wu, X.; Wu, C.; Xie, Y. Promoting Active Species Generation by Electrochemical Activation in Alkaline Media for Efficient Electrocatalytic Oxygen Evolution in Neutral Media. Nano Lett. 2017, 17, 578-583. 61. Zhang, B.; Lui, Y. H.; Zhou, L.; Tang, X.; Hu, S. An Alkaline Electro-Activated Fe-Ni Phosphide Nanoparticle-Stack Array for High-Performance Oxygen Evolution under Alkaline and Neutral Conditions. J. Mater. Chem. A 2017, 5, 13329-13335. 62. He, Z.; Mansfeld, F. Exploring the Use of Electrochemical Impedance Spectroscopy (Eis) in Microbial Fuel Cell Studies. Energy Environ. Sci. 2009, 2, 215-219. 63. Liu, X.; Park, M.; Kim, M. G.; Gupta, S.; Wu, G.; Cho, J. Integrating Nico Alloys with Their Oxides as Efficient Bifunctional Cathode Catalysts for Rechargeable Zinc-Air Batteries. Angew. Chem. Int. Ed. 2015, 54, 9654-9658.


24

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64. Zhao, X.; Zhang, H.; Yan, Y.; Cao, J.; Li, X.; Zhou, S.; Peng, Z.; Zeng, J. Engineering the Electrical Conductivity of Lamellar Silver-Doped Cobalt(II) Selenide Nanobelts for Enhanced Oxygen Evolution. Angew. Chem. Int. Ed. 2017, 56, 328-332. 65. Zhou, H.; Yu, F.; Sun, J.; Zhu, H.; Mishra, I. K.; Chen, S.; Ren, Z. Highly Efficient Hydrogen Evolution from Edge-Oriented WS2(1-x)Se2x Particles on Three-Dimensional Porous NiSe2 Foam. Nano Lett. 2016, 16, 7604-7609.


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Table of Contents Graphic

Self-Template Synthesis of Co-Se-S-O Hierarchical Nanotubes as Efficient Electrocatalysts for Oxygen Evolution under Alkaline and Neutral Conditions Zhi-Mei Luo, Jia-Wei Wang, Jing-Bo Tan, Zhi-Ming Zhang and Tong-Bu Lu We explore a facile self-template method for fabricating quaternary Co-Se-S-O nanotubes on carbon cloth for oxygen evolution reaction. It only requires low overpotentials of 230 mV and 480 mV to achieve 10 mA cm-2 current density at alkaline and neutral conditions, respectively, much superior to those of mono chalcogenide counterparts, as well as the commercial benchmark catalyst, IrO2.


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