Hierarchical Iron-Doped Nickel Diselenide Hollow Spheres for

Article Cite This: ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX

www.acsaem.org

Hierarchical Iron-Doped Nickel Diselenide Hollow Spheres for Efficient Oxygen Evolution Electrocatalysis Lifeng Lin, Min Chen, and Limin Wu* Department of Materials Science and State Key Laboratory of Molecular Engineering of Polymers, Fudan University, Shanghai 200433, China

Downloaded via 95.181.183.74 on July 19, 2019 at 00:35:41 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

S Supporting Information *

ABSTRACT: Explorin gearth-abundant oxygen evolution reaction electrocatalysts is attracting tremendous attention but still remains challenging. In this study, we design and synthesize hierarchical iron-doped nickel selenides with hollow structure and tunable composition. Benefiting from the synergistic effects of high specific surface area and optimal heteroatom doping, 5% Fe doped NiSe2 hollow spheres present excellent performances, exhibiting a 10 mA cm−2 current density at the overpotential as low as 231 mV and long-term stability for 20 h at 15 mA cm−2 in the basic medium. KEYWORDS: hierarchical hollow spheres, iron doped, nickel selenides, OER, electrocatalyst

■

INTRODUCTION To address the global energy crisis, tremendous efforts have been made to seek out sustainable energy sources to replace fossil fuels.1−6 As a renewable promising candidate, hydrogen (H2) possesses high gravimetric energy density and only produces water while releasing energy.7−9 In the electrolytic water splitting system, the production of hydrogen gas is severely hindered by the sluggish kinetics of oxygen evolution reaction (OER) even using the benchmark precious metal electrocatalysts (e.g., IrO2 and RuO2).10,11 Accordingly, it is very desirable to develop highly efficient non-noble metal electrocatalysts to lower the energy barrier for large-scale applications.12−15 As promising candidates to replace noble metal electrocatalysts, Ni-based electrocatalysts (e.g., oxides, hydroxides, chalcogenides, phosphides, and selenides) are intensively investigated in the water splitting system for OER because they are cost-effective and earth-abundant with excellent electrocatalytic capacity.16−18 Incorporation of hetero metal ions into Ni-based materials can further improve the electrocatalytic performance by modulating the intrinsic electronic structure. For instance, doping cerium into NiOx significantly enhanced its OER performance.19 Fe-doping into NiPS3 effectively decreased the energy barrier of the OER path and thus increased the electrocatalytic performance.20 Besides the doping strategy, fabricating different nanostructures to © XXXX American Chemical Society

expose more accessible sites is another efficient way to boost the OER process. For example, the mass activity of the Ni3N nanosheets was reported to be 10 times higher than the corresponding bulk material at overpotential of 0.5 V.21 The NiCoP/C nanoboxes derived from ZIF-67 nanocubes only required 330 mV to obtain a current density of 10 mA cm−2, comparable to many other electrocatalysts.22 Nickel selenide is widely regarded as a promising catalyst among Ni-based compounds owing to its excellent electrical conductivity and high electrocatalytic activity.23,24 Further doping iron into nickel selenide can enhance its catalytic property.25,26 In this study, we synthesize a series of hierarchical Fe-doped NiSe2 hollow spheres which have not been reported previously. The Ni and Fe contents in the Fedoped NiSe2 can be precisely tuned by the ingredients. Because of the positive effects of the doped Fe species and the unique nanostructure,27,28 the as-prepared hierarchical Fedoped NiSe2 hollow spheres only need overpotential of 231 mV to drive a current density of 10 mA cm−2 and exhibit excellent stability for 20 h in 1 M KOH, which are proporties superior to those of most of the previously reported electrocatalysts. Received: February 20, 2019 Accepted: June 17, 2019 Published: June 17, 2019 A

DOI: 10.1021/acsaem.9b00337 ACS Appl. Energy Mater. XXXX, XXX, XXX−XXX

Article

ACS Applied Energy Materials

■

The values of turnover frequency (TOF) can be calculated assuming that all Ni and Fe ions in the catalysts are active and contributed to the catalytic reaction (the lowest TOF values)

EXPERIMENTAL SECTION

Synthesis of Poly(styrene-co-acrylic acid) (PSA) Colloidal Spheres. Styrene (10 g), acrylic acid (1 g), and deionized water (120 g) were added into a 250 mL four-necked flask under mechanical stirring, deoxygenated by nitrogen bubble for 30 min, and then heated to 75 °C. After the injection of ammonium persulfate solution (0.18 g of ammonium persulfate dissolved in 10 mL of deionized water), this mixture was kept stirring for 18 h under N2 atmosphere to finish polymerization. The as-obtained PSA colloidal spheres were centrifuged, washed with water and ethanol several times, and then redispersed into ethanol (12 wt %) for further use. Synthesis of PSA@ NiFe Layered Double Hydroxide (LDH) Composite Spheres. A total of 1 mL of PSA colloidal spheres dispersion was diluted with 20 mL of deionized water and then added to 233 mg of Ni(NO3)2·6H2O and a certain amount of Fe(NO3)3· 9H2O according to the formulations in Table S1 under stirring. After that, 2-methylimidazole solution (131 mg of 2-methylimidazole dissolved in 5 mL of deionized water) was added dropwise into the mixture, and and the mixture was kept stirring at ambient temperature for 3 h. The products were collected by centrifugation and washed with ethanol for several times and then dried at 40 °C under vacuum. Synthesis of Hierarchical Fe-Doped NiSe2 Hollow Spheres. The obtained PSA@NiFe LDH composite spheres were transferred into a tube furnace and heated to 600 °C at a heating rate of 1 °C/ min and then kept at that temperature for 2 h under argon atmosphere to produce a black powder which was then placed in the tube furnace again with Se powder at the upstream side. The samples were annealed at 350 °C for 2 h under argon atmosphere to produce Fe-doped NiSe2 hollow spheres. Characterization. The structures and morphologies of all the samples were characterized with a transmission electron microscope (TEM) (FEI, Tecnai G2 20 TWIN, 200 kV) and scanning electronic microscope (SEM) (Zeiss, Ultra 55, 15 kV). The high-angle annular dark field−scanning transmission microscopy (HAADF-STEM) and energy dispersive spectroscopy (EDS) were carried out on a JEOL, JEM-2100F. The crystallographic information was recorded by powder X-ray diffraction (XRD) (Bruker, D8 Advance diffractometer with Cu Kα radiation λ = 1.5406 Å). Inductively coupled plasma− optical emission spectroscopy (ICP-OES) (Thermo Scientific, iCAP 7400) was used to determine the Ni and Fe contents of the samples. X-ray photoelectron spectroscopy (XPS) was performed on a scanning X-ray microprobe (ULVAC-PHI, PHI 5000C & PHI 5300), using C 1s (284.6 eV) as a reference. The nitrogen adsorption−desorption experiments were operated on a Micromeritics ASAP 2020 system at 77 K. A laser of 532 nm wavelength was used to measure the Raman spectroscopy spectrum (Renishaw, RM 2000). Electrochemical Measurements. All electrochemical measurements were performed on a CHI 760E electrochemistry workstation (CH Instruments) in a standard three electrode system at ambient temperature. A glassy carbon electrode (GCE) (area of 0.196 cm2), a saturated calomel electrode (SCE, in saturated KCl solution), and graphite rod were used as the working, reference, and counter electrodes, respectively. The catalyst ink was prepared by dispersing 3 mg of catalysts in 880 μL of ethanol and 120 μL of 5 wt % Nafion solution followed by ultrasonication for at least 30 min. Then, a certain volume of the catalyst ink was dropped on the glassy carbon electrode to reach the catalyst loading of 0.2 mg cm−2. All potentials were converted versus a reversible hydrogen electrode (RHE): E (vs RHE) = E (vs SCE) + (0.242 + 0.059 pH) V. Prior to all the linear sweep voltammetry (LSV) experiments, a resistance test was applied to compensate for the ohmic potential drop. LSV was recorded in 1 M KOH at a scan rate of 5 mV s−1 to obtain the polarization curves. Electrochemical impedance spectroscopy (EIS) measurements were performed with a frequency range from 0.1 to 100 000 Hz at an overpotential of 350 mV (vs RHE). Continuous cyclic voltammetry (CV) scanning from 1.1 to 1.8 V (vs RHE) at a scan rate of 50 mV s−1 was conducted to examine the electrochemical stability of the catalysts.

TOF = jS /(4Fn) Here, j (A/cm2) is the measured current density at an overpotential of 270 mV (1.50 V vs RHE); S (GCE area, 0.196 cm2) is the surface area of GCE; the number 4 means four electrons transferred in OER; F is the Faraday constant (96485.3 C mol−1), and n is the metal ions molar number (both Ni and Fe) calculated from the ICP results of the as-prepared catalysts.

■

RESULTS AND DISCUSSION Scheme 1 illustrates the schematic process of fabricating hierarchical Fe-doped NiSe2 hollow spheres. First, ∼350 nm Scheme 1. Schematic Illustration Process for Synthesis of Fe Doped NiSe2 Hollow Spheres

uniform PSA colloidal spheres (Figure S1) were synthesized according to our previously reported method,27 as templates. Then, 2-methylimidazole solution was added dropwise into the dispersion of PSA spheres and metal precursors to produce PSA@NiFe LDH composite spheres. TEM images revealed that PSA spheres were uniformly covered with a layer of LDH nanosheets, and the size of the nanosheets decreased with the increasing amount of iron precursors (Figure S2a−e). XRD patterns of the PSA@NiFe LDH composites clearly displayed that the diffraction peaks were basically consistent with the pure LDH phase (JCPDS No. 38-0715) (Figure S2f). After the coprecipitation and calcination under inert atmosphere, the PSA@NiFe LDH composites were converted to NiFe hollow spheres, which was confirmed by TEM images and XRD patterns (Figure S3). The as-prepared products were further selenized to obtain Fe-doped NiSe2 hollow spheres (denoted as Fe-NiSe2). Figure 1 presents typical SEM and TEM images of Fe-NiSe2 with various Fe doping amounts. Compared to NiFe hollow spheres (Figure S3a−e), although the sizes of the nanocrystals increase during the conversion from NiFe to Fe-NiSe2, the hollow and spherical structure can remain well, as shown by TEM images (insets, Figure 1). However, the nanoparticles are aggregating more seriously with the increasing iron content, accompanied by the decreasing specific surface area and average pore diameter (Figure S4). The XRD patterns demonstrate that the pristine NiSe2 and Fe-NiSe2 samples can all be indexed to NiSe2 (JCPDS No. 651843) without any additional peaks (Figure 2a), indicating that the incorporation of iron does not introduce any impurity. However, the peaks (200), (210), and (211) shift to the higher angle by increasing Fe amount in Fe-NiSe2 (Figure 2b), suggesting that the Fe species are indeed incorporated into B


Article


Figure 1. SEM images of Fe-NiSe2 hollow spheres: (a) 0, (b) 1%, (c) 3%, (d) 5%, and (e) 7% (inset: corresponding TEM images, scale bar: 100 nm).

Figure 2. (a) Typical XRD patterns of Fe-NiSe2 with different iron precursor amounts, (I) 0, (II) 1%, (III) 3%, (IV) 5%, and (V) 7%, and (b) the corresponding zoom-in regions showing evolution with Fe-doping.

into NiSe2, which can be further confirmed by the compositional line profile and EDS spectrum (Figures S6 and S7). Its high-resolution TEM presents the lattice fringes of 0.298, 0.267, and 0.243 nm (Figure 4b), which can be assigned to the interplane spacing of the (200), (210), and (211) planes of nickel selenide. The diffusing concentric rings in the selected area electron diffraction (SAED) pattern (Figure 4b inset) indicate the polycrystalline structure. The diffraction rings can be indexed to NiSe2, in agreement with the XRD analysis. However, the judgment of the intrinsic elements of the sample would be hampered by the Cu and C in the copper grid. Therefore, the EDS spectrum acquired by FESEM has also been obtained to confirm the existence of C and absence of Cu. Raman spectra (Figures 4c and S8) reveal two characteristic peaks at about 1350 and 1590 cm−1, corresponding to D and G bands of graphitic carbon,32 indicating that the nanoparticles are covered with graphitic carbon. The graphitic carbon can also be observed in Figure 4b, encapsulating on the surfaces of nanocrystals with a few layers, which can impart them with fast electron transfer ability to enhance electrocatalytic activity and protection of etching during the OER tests.22,33,34

NiSe2 crystals. The decrease of the crystal grain sizes can be ascribed to the lattice shrinkage induced by the substitution of Ni by Fe with smaller atom radius.20,26,28,29 The doping of Fe into NiSe2 can be also verified by XPS. As shown in Figure 3a, the Ni 2p3/2 region displays two dominant peaks of Ni(II)−Se and Ni(III)−O in which the Ni(III) species is ascribed to the inevitable surface oxidation exposed in the air.24,30 These peaks of Ni are visibly blue-shifted in Fe-NiSe2. The more the Fe, the higher the binding energy, indicating enhanced electron transfer.28,31 The high-resolution XPS spectra of Fe 2p3/2 and Se 3d (Figure 3b,c) also indicated iron has been introduced into the nickel selenides. Taking 5% Fe-NiSe2, for example, its high-resolution Fe 2p3/2 spectrum can be deconvoluted into two peaks centered at 710.7 and 712.2 eV, as shown in Figure S5a, corresponding to Fe−Se and Fe− O species, respectively. Also, the peaks centered at 54.9 and 57.7 eV can be assigned as Se−metal and Se−O species in the Se 3d spectrum (Figure S5b). Furthermore, with 5% Fe-NiSe2 hollow spheres as an example, the HAADF-STEM image and corresponding elemental mapping distinctly show homogeneous distribution of Ni, Fe, and Se (Figure 4a), indicating uniform doping of Fe C


Article


Figure 3. High resolution XPS spectra of (a) Ni 2p3/2, (b) Fe 2p3/2, and (c) Se 3d with different iron precursor amounts (I) 0, (II) 1%, (III) 3%, (IV) 5%, and (V) 7%.

polarization curve shows the characteristic oxidation peak at about 1.38 V, corresponding to the following reaction: Ni2+ + 3OH− → NiOOH + e− + H2O.20,35 After doping of Fe, the anodic peak of Ni2+/Ni3+ is suppressed and positively shifted to higher potential. As a result, the oxidation peak area should decrease along with the increasing introduction of Fe.36,37 However, the oxidation peak area of 5% Fe-NiSe2 seems to be larger than the 3% Fe-NiSe2. Compared to the other curves, this might be caused by the overlap of the oxidation region and the fast rise of catalysis current originated from high electrocatalytic activity.28,38−40 With the overpotential at the current density of 10 mA cm−2 (η10) as an indicator (Figure 5b), the electrocatalytic performances vary with the molar ratios of Fe/Ni in Fe-NiSe2. The η10 of primitive NiSe2 is 324 mV, while 5% Fe-NiSe2 only requires as low as 231 mV overpotential to achieve current density of 10 mA cm−2, which outperforms the commercial Ir/C (η10 of 312 mV) and most of the state-of-the-art OER electrocatalysts (Table S3). The overall OER process includes four elementary steps as follows: OH− + * → *OH + e− −

(1)

*OH + OH → *O + H 2O + e

−

(2)

*O + OH− → *OOH + e−

(3)

*OOH + OH− → * + O2 + H 2O + e−

(4)

Here, (*) denotes the NiSe2 or Fe-NiSe2 surface. The formation from *O to −OOH intermediates (step 3) is regarded as the rate-limiting step. The transitional metal Fe is capable of promoting the charge-transfer, thus altering the electronic structure of transitional metal-based electrocatalysts to activate the *O specie. Therefore, the much higher OER performance can be ascribed to the more active *O species and lower energy barrier of the OER path, due to the intrinsically improved electronic structure.28,41,42 The reason that adding a 5% amount of iron precursors causes the best performance in

Figure 4. (a) HAADF-STEM and corresponding elemental mapping images, (b) high-resolution TEM image and SAED (inset), and (c) Raman spectrum of 5% Fe-NiSe2 hollow spheres.

To investigate the OER performance in basic electrolyte, the as-prepared NiSe2 and Fe-NiSe2 hollow spheres were loaded on the GCE in a standard three-electrode system. Figure 5a displays the polarization curves with iR compensation obtained in 1 M KOH, with the commercial 20 wt % Ir/C catalyst (Premetek Co.) for comparison. For the original NiSe2, the D


Article


Figure 5. (a) Polarization curves, (b) overpotential required for j = 10 and 100 mA cm−2, (c) Tafel plots, and (d) TOFs at 270 and 300 mV of the Fe-NiSe2 electrocatalysts.

Figure 6. (a) Mass activities at η = 270 mV and (b) normalized polarization curves by ECSA of Fe-NiSe2 electrocatalysts.

270 mV, the TOF value of 5% Fe-NiSe2 is 0.052 s−1, much higher than those of the primitive NiSe2 and other Fe-NiSe2 catalysts (Figure 5d). Further increasing the overpotential to 300 mV even boosts the TOF value to 0.107 s−1. All these results indicate that the 5% Fe-NiSe2 catalyst possesses excellent electrocatalytic performance toward OER owing to appropriate doping amount of Fe. In addition, the mass activity calculated from the current density at a specific overpotential is another important parameter to display the electrocatalytic activity of catalysts.44,45 It can be found that the mass activity has a similar trend as that of the TOF value at the overpotential of 270 mV (Figure 6a). The mass activity increases with the increasing Fe proportion in NiSe2 and reaches the maximum value in 5% FeNiSe2 catalyst but declines sharply if more iron is introduced. Also, the EIS measurements revealed that the metal selenide electrocatalysts present small charge transfer resistance,

OER is the optimized electronic structure modulated by the appropriate content of iron. Besides, the polarization curves of 5% Fe-NiSe2 were also tested with different loading amounts onto GCE to confirm the optimal value of 0.2 mg cm−2 (Figure S9). Generally, the catalytic kinetics can be estimated by the Tafel plots (η versus log (j), η is the overpotential and j represents the current density). As illustrated in Figure 5c, the 5% Fe-NiSe2 shows the lowest Tafel slope of 83 mV dec−1 among all the tested samples, implying the fastest kinetics of mass and electron transfer. TOF is another important parameter to gain insight into the intrinsic activity30,43 and can be calculated based on ICP results (Table S1) at different overpotentials, assuming all the metal sites (including Ni and Fe) are active. It is noteworthy that this TOF is the lowest estimate because not all the metal sites are accessible and electrochemically active. Particularly, at the overpotential of E


Article


Figure 7. (a) Polarization curves of 5% Fe-NiSe2 hollow spheres recorded before and after 1000 cycles at a scan rate of 50 mV s−1 from 1.1 to 1.8 V (vs RHE) and (b) chronopotentiometry response of 5% Fe-NiSe2 hollow spheres at the current density of 15 mA cm−2 (inset: the production of O2 bubbles on the surface of the electrode).

XPS was employed. As shown in Figure S19, in the Ni 2p3/2 and Fe 2p3/2 regions, peaks of metal−Se disappeared and transformed into oxidized species after the OER test because of the oxidation during the test. The slight shift of Se−metal bonds can be ascribed to the surface oxidation.48 The peak centered at 531.8 eV originated from the surface oxidation in the form of the metal−OH bond, because of the formation of highly active NiFe hydroxide species during OER. Such in situ formed surface hydroxide species are considered to be the catalytic sites for the oxidation of OH− to O2.49,50 Therefore, the metallic selenides in the in situ formed core−shell heterostructure serve as the substrate for the fast electron transport, resulting in the excellent OER performance. Such good stability with excellent performance enables the hierarchical Fe-NiSe2 hollow spheres to be one of the promising candidates for practical electrocatalytic applications.

suggesting fast electron transfer during the OER process (Figure S10). Especially after the introduction of Fe, Rct decreases dramatically from 53.32 Ω (NiSe2) to 5.43 Ω (7% Fe-NiSe2), indicating the promotion of charge transfer (Table S2). To eliminate the contribution of the size, shape, or morphology to electrocatalytic activity, the polarization curves have been normalized by electrochemically active surface area (ECSA) (Figure S11).46,47 As shown in Figure 6b, the 5% FeNiSe2 still considerably outperforms other catalysts, especially the original NiSe2, further confirming that doping of Fe plays a crucial role in improving the OER activity of NiSe2. A similar conclusion can also be obtained from the polarization curves normalized by specific surface area as shown in Figure S12. On the other hand, the hierarchical hollow structure also contributes to the high performance of 5% Fe-NiSe2. To verify it, 5% Fe-NiSe2 nanoparticles were prepared for comparison and confirmed by the TEM images and XRD pattern (Figure S13). Without hierarchical hollow structure, 5% Fe-NiSe2 nanoparticles possess much smaller specific surface area (Figure S14) and lower OER activity (η10 = 263 mV, η100 = 379 mV, Figure S15) than the hollow spheres (η10 = 231 mV, η100 = 360 mV, Figure 5b). Long-term stability is also a key criterion to evaluate the superiority of electrocatalysts. The 5% Fe-NiSe2 hollow spheres were tested by using CV cycling and chronopotentiometry in 1 M KOH. As shown in Figure 7a, after 1000 cycles, almost negligible decay is observed in the polarization curves recorded. Durability can be further confirmed by the inconspicuous decline during 20 h of chronopotentiometry measurement at the current density of 15 mA cm−2 (Figures 7b and S16). The slight decline of OER activity might be originated from the electrocatalysts peel-off from the electrode due to the constantly escaping bubbles and the leach of Se. After the long-term OER test, the morphology of the hollow structure remained intact (Figure S17a), although a small amount of surface metal selenides were oxidized to amorphous NiFe hydroxides (Figure S17b).20,48 XRD patterns showed no significant differences, implying that the crystal structure were well-retained (Figure S18a). According to the EDS spectrum recorded after the durability test (Figure S18b), the relative content of oxygen obviously increased due to the surface oxidation during operation. To further investigate the compositional variation at the surface during the OER test,

■

CONCLUSION In summary, we have demonstrated the rational design of irondoped nickel selenide spheres with hierarchical hollow structure and tunable composition. Owing to the synergistic effect of large surface area and Fe doping, the optimal Fe-NiSe2 hollow spheres exhibit an overpotential of as low as 231 mV at 10 mA cm−2 and long-term durability in 1 M KOH, which is superior to those of most of the previously reported non-noble metal OER electrocatalysts. Based on this study, we can not only synthesize a series of earth-abundant efficient electrocatalysts toward OER but also get fundamental insight into the nanostructure−composition−performance relationship of the electrocatalytic materials.

■

ASSOCIATED CONTENT

* Supporting Information S

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsaem.9b00337.

■

Characterization data (TEM, SEM, Raman spectra, XRD, XPS, electrochemical measurement tests, and so forth) and comparison of catalytic activity of various OER catalysts (PDF)

AUTHOR INFORMATION

Corresponding Author

*(L.W.) E-mail: [email protected]. F


Article

ACS Applied Energy Materials ORCID

Oxide Nanoparticles as High-Performance Catalysts for Electrochemical Water Splitting. Adv. Funct. Mater. 2014, 24, 3123−3129. (17) Luan, C.; Liu, G.; Liu, Y.; Yu, L.; Wang, Y.; Xiao, Y.; Qiao, H.; Dai, X.; Zhang, X. Structure Effects of 2D Materials on alpha-Nickel Hydroxide for Oxygen Evolution Reaction. ACS Nano 2018, 12, 3875−3885. (18) Sun, H.; Xu, X.; Yan, Z.; Chen, X.; Cheng, F.; Weiss, P. S.; Chen, J. Porous Multishelled Ni2P Hollow Microspheres as an Active Electrocatalyst for Hydrogen and Oxygen Evolution. Chem. Mater. 2017, 29, 8539−8547. (19) Ng, J. W. D.; García-Melchor, M.; Bajdich, M.; Chakthranont, P.; Kirk, C.; Vojvodic, A.; Jaramillo, T. F. Gold-supported ceriumdoped NiOx catalysts for water oxidation. Nat. Energy 2016, 1, 16053. (20) Liang, Q.; Zhong, L.; Du, C.; Luo, Y.; Zheng, Y.; Li, S.; Yan, Q. Achieving highly efficient electrocatalytic oxygen evolution with ultrathin 2D Fe-doped nickel thiophosphate nanosheets. Nano Energy 2018, 47, 257−265. (21) Xu, K.; Chen, P.; Li, X.; Tong, Y.; Ding, H.; Wu, X.; Chu, W.; Peng, Z.; Wu, C.; Xie, Y. Metallic nickel nitride nanosheets realizing enhanced electrochemical water oxidation. J. Am. Chem. Soc. 2015, 137, 4119−4125. (22) He, P.; Yu, X. Y.; Lou, X. W. Carbon-Incorporated NickelCobalt Mixed Metal Phosphide Nanoboxes with Enhanced Electrocatalytic Activity for Oxygen Evolution. Angew. Chem., Int. Ed. 2017, 56, 3897−3900. (23) Nagaraju, G.; Cha, S. M.; Sekhar, S. C.; Yu, J. S. Metallic Layered Polyester Fabric Enabled Nickel Selenide Nanostructures as Highly Conductive and Binderless Electrode with Superior Energy Storage Performance. Adv. Energy Mater. 2017, 7, 1601362. (24) Fang, Z.; Peng, L.; Lv, H.; Zhu, Y.; Yan, C.; Wang, S.; Kalyani, P.; Wu, X.; Yu, G. Metallic Transition Metal Selenide Holey Nanosheets for Efficient Oxygen Evolution Electrocatalysis. ACS Nano 2017, 11, 9550−9557. (25) Xu, X.; Song, F.; Hu, X. A nickel iron diselenide-derived efficient oxygen-evolution catalyst. Nat. Commun. 2016, 7, 12324. (26) Gu, C.; Hu, S.; Zheng, X.; Gao, M. R.; Zheng, Y. R.; Shi, L.; Gao, Q.; Zheng, X.; Chu, W.; Yao, H. B.; Zhu, J.; Yu, S. H. Synthesis of Sub-2 nm Iron-Doped NiSe2 Nanowires and Their SurfaceConfined Oxidation for Oxygen Evolution Catalysis. Angew. Chem., Int. Ed. 2018, 57, 4020−4024. (27) Zhao, Y.; Hu, L.; Gao, S.; Liao, M.; Sang, L.; Wu, L. One-Step Self-Assembly Fabrication of High Quality NixMg1‑xO Bowl-Shaped Array Film and Its Enhanced Photocurrent by Mg2+Doping. Adv. Funct. Mater. 2015, 25, 3256−3263. (28) Zhang, B.; Lui, Y. H.; Ni, H.; Hu, S. Bimetallic (FexNi1‑x)2 P nanoarrays as exceptionally efficient electrocatalysts for oxygen evolution in alkaline and neutral media. Nano Energy 2017, 38, 553−560. (29) Huang, H.; Yu, C.; Zhao, C.; Han, X.; Yang, J.; Liu, Z.; Li, S.; Zhang, M.; Qiu, J. Iron-tuned super nickel phosphide microstructures with high activity for electrochemical overall water splitting. Nano Energy 2017, 34, 472−480. (30) Nai, J.; Lu, Y.; Yu, L.; Wang, X.; Lou, X. W. D. Formation of Ni-Fe Mixed Diselenide Nanocages as a Superior Oxygen Evolution Electrocatalyst. Adv. Mater. 2017, 29, 1703870. (31) Liu, G.; Gao, X.; Wang, K.; He, D.; Li, J. Mesoporous nickeliron binary oxide nanorods for efficient electrocatalytic water oxidation. Nano Res. 2017, 10, 2096−2105. (32) Li, J. S.; Wang, Y.; Liu, C. H.; Li, S. L.; Wang, Y. G.; Dong, L. Z.; Dai, Z. H.; Li, Y. F.; Lan, Y. Q. Coupled molybdenum carbide and reduced graphene oxide electrocatalysts for efficient hydrogen evolution. Nat. Commun. 2016, 7, 11204. (33) Xu, Y.; Tu, W.; Zhang, B.; Yin, S.; Huang, Y.; Kraft, M.; Xu, R. Nickel Nanoparticles Encapsulated in Few-Layer Nitrogen-Doped Graphene Derived from Metal-Organic Frameworks as Efficient Bifunctional Electrocatalysts for Overall Water Splitting. Adv. Mater. 2017, 29, 1605957. (34) Ma, Y.-Y.; Wu, C.-X.; Feng, X.-J.; Tan, H.-Q.; Yan, L.-K.; Liu, Y.; Kang, Z.-H.; Wang, E.-B.; Li, Y.-G. Highly efficient hydrogen

Min Chen: 0000-0002-6422-9942 Limin Wu: 0000-0001-8495-8627 Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS We appreciate the financial support provided for this research by the National Key Research and Development Program of China (2017YFA0204600) and the National Natural Science Foundation of China (51721002 and 51673045).

■

REFERENCES

(1) Dresselhaus, M. S.; Thomas, I. L. Alternative energy technologies. Nature 2001, 414, 332−337. (2) Aricò, A. S.; Bruce, P.; Scrosati, B.; Tarascon, J.-M.; van Schalkwijk, W. Nanostructured materials for advanced energy conversion and storage devices. Nat. Mater. 2005, 4, 366−377. (3) Chen, H.; Hu, L.; Chen, M.; Yan, Y.; Wu, L. Nickel-Cobalt Layered Double Hydroxide Nanosheets for High-performance Supercapacitor Electrode Materials. Adv. Funct. Mater. 2014, 24, 934−942. (4) Zhao, Y.; Hu, L.; Zhao, S.; Wu, L. Preparation of MnCo2O4@ Ni(OH)2Core-Shell Flowers for Asymmetric Supercapacitor Materials with Ultrahigh Specific Capacitance. Adv. Funct. Mater. 2016, 26, 4085−4093. (5) Xie, H.; Chen, M.; Wu, L. Hierarchical TiO2/SnO2 Hollow Spheres Coated with Graphitized Carbon for High-Performance Electrochemical Li-Ion Storage. Small 2017, 13, 1604283. (6) Xie, H.; Hu, L.; Wu, F.; Chen, M.; Wu, L. Self-Templated Synthesis of Ultrathin Nanosheets Constructed TiO2 Hollow Spheres with High Electrochemical Properties. Adv. Sci. 2016, 3, 1600162. (7) Debe, M. K. Electrocatalyst approaches and challenges for automotive fuel cells. Nature 2012, 486, 43−51. (8) Turner, J. A. Sustainable Hydrogen Production. Science 2004, 305, 972−974. (9) Zou, X.; Zhang, Y. Noble metal-free hydrogen evolution catalysts for water splitting. Chem. Soc. Rev. 2015, 44, 5148−5180. (10) Han, L.; Dong, S.; Wang, E. Transition-Metal (Co, Ni, and Fe)Based Electrocatalysts for the Water Oxidation Reaction. Adv. Mater. 2016, 28, 9266−9291. (11) Subbaraman, R.; Tripkovic, D.; Chang, K. C.; Strmcnik, D.; Paulikas, A. P.; Hirunsit, P.; Chan, M.; Greeley, J.; Stamenkovic, V.; Markovic, N. M. Trends in activity for the water electrolyser reactions on 3d M(Ni,Co,Fe,Mn) hydr(oxy)oxide catalysts. Nat. Mater. 2012, 11, 550−557. (12) Zhang, J.; Wang, T.; Liu, P.; Liao, Z.; Liu, S.; Zhuang, X.; Chen, M.; Zschech, E.; Feng, X. Efficient hydrogen production on MoNi4 electrocatalysts with fast water dissociation kinetics. Nat. Commun. 2017, 8, 15437. (13) Zhang, P.; Li, L.; Nordlund, D.; Chen, H.; Fan, L.; Zhang, B.; Sheng, X.; Daniel, Q.; Sun, L. Dendritic core-shell nickel-iron-copper metal/metal oxide electrode for efficient electrocatalytic water oxidation. Nat. Commun. 2018, 9, 381. (14) Hu, F.; Zhu, S.; Chen, S.; Li, Y.; Ma, L.; Wu, T.; Zhang, Y.; Wang, C.; Liu, C.; Yang, X.; Song, L.; Yang, X.; Xiong, Y. Amorphous Metallic NiFeP: A Conductive Bulk Material Achieving High Activity for Oxygen Evolution Reaction in Both Alkaline and Acidic Media. Adv. Mater. 2017, 29, 1606570. (15) Lin, L.; Chen, M.; Wu, L. Synthesis of Molybdenum-Tungsten Bimetallic Carbide Hollow Spheres as pH-Universal Electrocatalysts for Efficient Hydrogen Evolution Reaction. Adv. Mater. Interfaces 2018, 5, 1801302. (16) Fominykh, K.; Feckl, J. M.; Sicklinger, J.; Döblinger, M.; Böcklein, S.; Ziegler, J.; Peter, L.; Rathousky, J.; Scheidt, E.-W.; Bein, T.; Fattakhova-Rohlfing, D. Ultrasmall Dispersible Crystalline Nickel G


Article

ACS Applied Energy Materials evolution from seawater by a low-cost and stable CoMoP@C electrocatalyst superior to Pt/C. Energy Environ. Sci. 2017, 10, 788−798. (35) Li, Y.; Zhao, C. Iron-Doped Nickel Phosphate as Synergistic Electrocatalyst for Water Oxidation. Chem. Mater. 2016, 28, 5659− 5666. (36) Fominykh, K.; Chernev, P.; Zaharieva, I.; Sicklinger, J.; Stefanic, G.; Döblinger, M.; Müller, A.; Pokharel, A.; Böcklein, S.; Scheu, C.; Bein, T.; Fattakhova-Rohlfing, D. Iron-Doped Nickel Oxide Nanocrystals as Highly Efficient Electrocatalysts for Alkaline Water Splitting. ACS Nano 2015, 9, 5180−5188. (37) Yin, S.; Tu, W.; Sheng, Y.; Du, Y.; Kraft, M.; Borgna, A.; Xu, R. A Highly Efficient Oxygen Evolution Catalyst Consisting of Interconnected Nickel-Iron-Layered Double Hydroxide and Carbon Nanodomains. Adv. Mater. 2018, 30, 1705106. (38) Trotochaud, L.; Young, S. L.; Ranney, J. K.; Boettcher, S. W. Nickel-iron oxyhydroxide oxygen-evolution electrocatalysts: the role of intentional and incidental iron incorporation. J. Am. Chem. Soc. 2014, 136, 6744−6753. (39) Yan, K.; Sheng, M.; Sun, X.; Song, C.; Cao, Z.; Sun, Y. Microwave Synthesis of Ultrathin Nickel Hydroxide Nanosheets with Iron Incorporation for Electrocatalytic Water Oxidation. ACS Appl. Energy Mater. 2019, 2, 1961−1968. (40) Zhou, Q.; Chen, Y.; Zhao, G.; Lin, Y.; Yu, Z.; Xu, X.; Wang, X.; Liu, H. K.; Sun, W.; Dou, S. X. Active-Site-Enriched Iron-Doped Nickel/Cobalt Hydroxide Nanosheets for Enhanced Oxygen Evolution Reaction. ACS Catal. 2018, 8, 5382−5390. (41) Sun, F.; Wang, G.; Ding, Y.; Wang, C.; Yuan, B.; Lin, Y. NiFeBased Metal-Organic Framework Nanosheets Directly Supported on Nickel Foam Acting as Robust Electrodes for Electrochemical Oxygen Evolution Reaction. Adv. Energy Mater. 2018, 8, 1800584. (42) Abbott, D. F.; Fabbri, E.; Borlaf, M.; Bozza, F.; Schäublin, R.; Nachtegaal, M.; Graule, T.; Schmidt, T. J. Operando X-ray absorption investigations into the role of Fe in the electrochemical stability and oxygen evolution activity of Ni1‑xFexOy nanoparticles. J. Mater. Chem. A 2018, 6, 24534−24549. (43) Yan, L.; Cao, L.; Dai, P.; Gu, X.; Liu, D.; Li, L.; Wang, Y.; Zhao, X. Metal-Organic Frameworks Derived Nanotube of Nickel-Cobalt Bimetal Phosphides as Highly Efficient Electrocatalysts for Overall Water Splitting. Adv. Funct. Mater. 2017, 27, 1703455. (44) Huang, J.; Chen, J.; Yao, T.; He, J.; Jiang, S.; Sun, Z.; Liu, Q.; Cheng, W.; Hu, F.; Jiang, Y.; Pan, Z.; Wei, S. CoOOH Nanosheets with High Mass Activity for Water Oxidation. Angew. Chem., Int. Ed. 2015, 54, 8722−8727. (45) 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. (46) Chen, Y. Y.; Zhang, Y.; Jiang, W. J.; Zhang, X.; Dai, Z.; Wan, L. J.; Hu, J. S. Pomegranate-like N,P-Doped Mo2C@C Nanospheres as Highly Active Electrocatalysts for Alkaline Hydrogen Evolution. ACS Nano 2016, 10, 8851−8860. (47) Anantharaj, S.; Ede, S. R.; Karthick, K.; Sam Sankar, S.; Sangeetha, K.; Karthik, P. E.; Kundu, S. Precision and correctness in the evaluation of electrocatalytic water splitting: revisiting activity parameters with a critical assessment. Energy Environ. Sci. 2018, 11, 744−771. (48) Panda, C.; Menezes, P. W.; Walter, C.; Yao, S.; Miehlich, M. E.; Gutkin, V.; Meyer, K.; Driess, M. From a Molecular 2Fe-2Se Precursor to a Highly Efficient Iron Diselenide Electrocatalyst for Overall Water Splitting. Angew. Chem., Int. Ed. 2017, 56, 10506− 10510. (49) Bates, M. K.; Jia, Q.; Doan, H.; Liang, W.; Mukerjee, S. ChargeTransfer Effects in Ni-Fe and Ni-Fe-Co Mixed-Metal Oxides for the Alkaline Oxygen Evolution Reaction. ACS Catal. 2016, 6, 155−161. (50) Wang, T.; Nam, G.; Jin, Y.; Wang, X.; Ren, P.; Kim, M. G.; Liang, J.; Wen, X.; Jang, H.; Han, J.; Huang, Y.; Li, Q.; Cho, J. NiFe (Oxy) Hydroxides Derived from NiFe Disulfides as an Efficient

Oxygen Evolution Catalyst for Rechargeable Zn-Air Batteries: The Effect of Surface S Residues. Adv. Mater. 2018, 30, 1800757.

H


Hierarchical Iron-Doped Nickel Diselenide Hollow Spheres for

Recommend Documents