One-Step Growth of IronâNickel Bimetallic Nanoparticles on FeNi

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One-Step Growth of Iron−Nickel Bimetallic Nanoparticles on FeNi Alloy Foils: Highly Efficient Advanced Electrodes for the Oxygen Evolution Reaction Umair Yaqub Qazi,†,§ Cheng-Zong Yuan,†,§ Naseeb Ullah,† Yi-Fan Jiang,† Muhammad Imran,† Akif Zeb,† Sheng-Jie Zhao,† Rahat Javaid,‡ and An-Wu Xu*,† †

Division of Nanomaterials and Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, P. R. China ‡ Fukushima Renewable Energy Institute, National Institute of Advanced Industrial Science and Technology, AIST, 2-2-9 Machiikedai, Koriyama, Fukushima 963-0298, Japan S Supporting Information *

ABSTRACT: Electrochemical water splitting is an important process to produce hydrogen and oxygen for energy storage and conversion devices. However, it is often restricted by the oxygen evolution reaction (OER) due to its sluggish kinetics. To overcome the problem, precious metal oxide-based electrocatalysts, such as RuO2 and IrO2, are widely used. The lack of availability and the high cost of precious metals compel researchers to find other resources for the development of cost-effective, environmentally friendly, earth-abundant, nonprecious electrocatalysts for OER. Such catalysts should have high OER performance and good stability in comparison to those of available commercial precious metal-based electrocatalysts. Herein, we report an inexpensive fabrication of bimetallic iron− nickel nanoparticles on FeNi-foil (FeNi4.34@FeNi-foil) as an integrated OER electrode using a one-step calcination process. FeNi4.34@FeNi-foil obtained at 900 °C shows superior OER activity in alkaline solution with an overpotential as low as 283 mV to achieve a current density of 10 mA cm−2 and a small Tafel slope of 53 mV dec−1. The high performance and durability of the as-prepared nonprecious metal electrode even exceeds those of the available commercial RuO2 and IrO2 catalysts, showing great potential in replacing the expensive noble metal-based electrocatalysts for OER. KEYWORDS: one-step growth, iron−nickel bimetallic nanoparticles, oxygen evolution reaction (OER), self-supported electrode, water splitting, electrocatalysis

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contributor as an energy carrier in future hydrogen economy.10 Electrochemical water splitting provides a prominent solution for the production of hydrogen from renewable resources, such as wind power and solar energy.11 However, the hydrogen production efficiency faces limitations in OER as water splitting is a thermodynamic uphill reaction involving stepwise fourelectron transfer with a large overpotential, which is higher than the minimum theoretical value of 1.23 V.12,13 To overcome the problem of large overpotential for water splitting, it is of crucial interest to develop an efficient catalyst that accelerates the reaction rate and lowers the energy consumption at a low overpotential value.14 The available commercial OER electrocatalysts still based on the use of noble metal/metal oxides, such as IrO2 and RuO2, and considered as the most efficient electrocatalysts.15−17 However, these catalysts are hindered to be used in large-scale industrial applications due to the scarcity

INTRODUCTION The increasing demand for developing highly efficient energy conversion devices, which are suitable for the conservation of the natural environment, is a critical issue in the current era. The nonrenewable natural resources, such as gas, oil, and coal, are depleting rapidly. They are also the primary contributor to the environmental pollution in the atmosphere. Because of these reasons, modern society is moving toward clean energy resources that are shown to be of great interest in renewable energy projects based on energy conversion and storage technologies.1,2 As an alternative source of sustainable energy, researchers are focusing on new strategies to develop efficient energy storage devices.3−5 Among many other scientific approaches, electrocatalytic water splitting is considered as a promising strategy to produce clean energy through the hydrogen evolution reaction and oxygen evolution reaction (OER) in the presence of an efficient catalyst.6 OER is a key half-reaction in water splitting for hydrogen production.7−9 As a chemical fuel, hydrogen is an ideal candidate for clean energy replacement for many industrial processes and could be a major © XXXX American Chemical Society

Received: June 21, 2017 Accepted: August 11, 2017

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DOI: 10.1021/acsami.7b08922 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

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ACS Applied Materials & Interfaces and high cost.18,19 Over the last few decades, tremendous efforts have been made in exploring highly efficient and durable nonprecious metal catalysts, such as earth-abundant, low cost, 3d transition metals, oxides, and their derivatives, such as Fe, Co, Ni, CoOx, and MoOx.20−26 These nonprecious metals with different structures are supposed to be a good choice as an alternative to noble metals because of their low cost and high theoretical activity.27−30 Although more complex electrocatalysts have been investigated for OER activity on a series of perovskite oxides, but Ba0.5Sr0.5Co0.8Fe0.2O3.5 showed the highest activity.31,32 Most recently, a FeNi-based bimetallic system has been studied and found to be an active OER catalyst.33 The FeNi double-layered hydroxide (FeNi-LDH) catalysts are reported as efficient electrocatalysts coupled with multiwalled carbon nanotubes for water oxidation.34 However, research has been continuing for further improvement of the activity as well as the sustainability of the FeNi-LDH catalyst. Current research developments have proved that the embodiment of Fe into nickel-based materials could enhance the OER efficiency by changing the local electronic framework of the catalyst.35−38 Apart from this, a combination of the active catalyst with conductive substrates can be helpful for charge transfer and plays an efficient role for OER activity and durability.39−41 It has been well-understood that the surface area of a catalyst will strongly impact the mass activity. It means that nanoscale catalytic materials with a smaller size can have more active sites to gain higher OER activity based on mass.42 Hence, we can fabricate binary metal nanoparticle (NP) catalysts within nanoscale size and get a higher OER efficiency in electrochemical cells. However, fewer research studies have been extended to smaller-size bimetallic FeNi NPs as OER electrocatalysts. Our previous research finding demonstrated that Fe-doped nickel sulfide (Fe-Ni3S2) on FeNi-foil works as an efficient OER electrode, where FeNi-foil acts as a conductive substrate that could effectively enhance the electrocatalytic activity and durability of the catalyst.43 Herein, we present one-step growth of FeNi4.34 bimetallic NPs supported on a highly conductive FeNi alloy foil as an efficient electrode for OER via high-temperature calcination under an ammonia environment. The FeNi alloy foil works as a source of Fe, Ni, and the current collector. The FeNi4.34 NPs are uniformly spread on the conductive surface of FeNi-foil, providing a large amount of surface active sites that further increases the electron transfer kinetics of water oxidation. As a result, the FeNi4.34@FeNi-foil electrode shows noteworthy electrocatalytic activity and efficient long-term stability for OER with a low onset potential of only 1.474 V versus reversible hydrogen electrode (RHE). Moreover, the fabrication of highly efficient FeNi4.34 NPs on a conductive substrate has the potential for future energy conversion and storage applications.

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then washed with ethanol and deionized water at least three times. After that, the foil was calcined at 900 °C for 3 h in a continuous ammonia (NH3) gas flow with a heating rate of 5 °C min−1. Finally, the FeNi4.34 NPs on the FeNi-foil (denoted FeNi4.34@FeNi-foil) were obtained and used for further characterization. To find out the best electrocatalytic activity for OER, the same procedure was adopted at various temperatures and the samples were prepared at 400, 600, 800, and 1000 °C. The formation process of FeNi alloy NPs in an Ar atmosphere was also carried out under control experimental conditions. Characterization. X-ray powder diffraction (XRD) patterns were recorded on a Rigaku/Max-3A X-ray diffractometer with Cu Kα radiation (λ = 1.54178 Å). Scanning electron microscopy (SEM) images of the samples and energy-dispersive spectrometry (EDS) elemental mappings were obtained on a field-emission scanning electron microscope (JSM-6701F; JEOL) operated at an accelerating voltage of 5 kV. Transmission electron microscopic (TEM) images and high-resolution transmission electron microscopic (HRTEM) images were acquired on a JEOL-2010 microscope with an accelerating voltage of 200 kV. X-ray photoelectron spectroscopy (XPS) was performed at the photoemission endstation in the National Synchrotron Radiation Laboratory (Hefei, China). The ratio of the Fe and Ni content in the FeNi4.34 NPs was measured by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) on a PerkinElmer Optima 8000 ICP-AES/ICP-OES spectrometer. Electrochemical Measurements. A standard three-electrode system controlled by a CHI 660E electrochemical workstation (CH Instruments, Inc., Shanghai) was used for electrochemical measurements at room temperature. In the three-electrode system, the asprepared FeNi4.34@FeNi-foil electrode was kept as the working electrode, a platinum wire as the counter electrode, and a saturated Ag/AgCl electrode as the reference electrode. Prior to perform the electrochemical measurement, the electrolyte (1 M KOH, pH = 14) solution was saturated with oxygen by continuous bubbling of oxygen gas for 30 min. The polarization curves were recorded by linear sweep voltammetry (LSV) with a sweep rate of 5 mV s−1 . The electrochemical impedance spectroscopy (EIS) measurements were performed under the same configuration at an overpotential of 324 mV from 106 to 0.01 Hz with an alternating current voltage of 5 mV. An IrO2-loaded electrode was prepared by dispersing 2 mg of IrO2 and 10 μL of 5 wt % Nafion solutions into 1 mL of ethanol, and sonication was done for several minutes to form an ink. Then, 20 μL of the catalyst ink was drop-casted on the glassy carbon electrode. All potentials measured were calibrated to the reversible hydrogen electrode (RHE) using the following equation: ERHE = EAg/AgCl + 0.197 V + 0.059 × pH and were not compensated for iR loss.

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RESULTS AND DISCUSSION Herein, we investigate the direct growth of Ni-rich FeNi alloy NPs formed on a FeNi-foil (FeNi4.34@FeNi-foil) where the Scheme 1. Schematic Illustration of the Preparation of FeNi4.34@FeNi-Foil as a Highly Efficient Electrode for OER

EXPERIMENTAL SECTION

Materials. Hydrochloric acid (HCl), ethanol, and potassium hydroxide (KOH) were acquired from Aladdin Ltd. (Shanghai, China). Nafion (5 wt %) was purchased from Sigma-Aldrich Chemical Reagent Co., Ltd. FeNi alloy foils (atomic ratio of Fe to Ni was 1:3.8) were received from Shanxi Shengyuan Metal Material Co., Ltd., China. All chemicals were of analytical grade and used as received without further purification. In all experiments, deionized water from a Millipore system was used for sample preparations. Preparation of FeNi4.34@FeNi-Foil. To ensure that the FeNi alloy foil (1 × 3 cm2) surfaces are free from impurities, the foil was immersed into 6 M HCl solution for 10 min under sonication and

FeNi-foil works as metal sources and the current collector. Initially, a series of experiments were performed to find out the optimized conditions for the synthesis of the best active material. A well-cleaned pretreated FeNi-foil was used for calcination at various temperatures ranging from 400 to 1000 B


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(220) planes of FeNi4.34, respectively, correspond with FeNi JCPDS # 03-1109. It is observed that the XRD spectrum of asprepared FeNi alloy NPs shows one single phase with a slight shift in the peak position but is closer to the pure Ni spectra as the prepared FeNi NPs are rich in Ni atoms. This small shift is indicating Fe consolidation into the lattice of Ni. Because of the different ionic radius of Fe, the lattice is perverted and a small shift in the peak position was observed.44 Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to investigate the morphology, size, and surrounding of the particles formed on FeNi-foil. Figure 2a,b shows the SEM images of FeNi-foil before and after calcination. The FeNi alloy NPs were formed and fully spread on the surface of FeNi-foil. TEM images display the clear view, as shown in Figure 2c, and the results are corresponding to the SEM image. The histogram of the FeNi alloy NP size distribution was recorded by measuring the size of 100 particles in a random area of the sample. Figure S4 (Supporting Information) shows a relatively narrow particle size distribution with an average size of ≈6 ± 1 nm. Yu et al. and Robinson et al. also observed the narrow size distribution of FeNi alloy particles.44,45 The high-resolution TEM (HRTEM) image taken from a single FeNi alloy NP is circled with a square, as shown in Figure 2d. Furthermore, we employed the elemental mapping technique to verify the element distribution of FeNi NPs associated with the SEM image (Figure 2e), and elemental mappings (Figure 2f,g) reveal the highly homogeneous distribution of the Fe and Ni atoms, indicating that FeNi NPs were fabricated with an atomic ratio of Fe to Ni of about 1:4.65. The EDS spectrum is shown in Figure S5 (Supporting Information). X-ray photoelectron spectroscopy (XPS) has been employed to get some information on the elemental composition and states of the outer surface of materials. Keeping these points in our mind, we have investigated the elemental composition and oxidation states of FeNi4.34 NPs. A survey spectrum of XPS confirms the presence of Fe and Ni atoms in the FeNi4.34@ FeNi-foil (Figure S6), and the atomic ratio of Fe to Ni is about 1:4.34, which is in line with the inductively coupled plasma-

Figure 1. XRD pattern for as-prepared FeNi4.34@FeNi, where Ni-rich FeNi4.34@FeNi-foil shows the peak position influenced toward JCPDS # 03-1109.

°C for 3 h under the continuous flow of ammonia (NH3) gas, as clearly shown in Scheme 1 and Figure S1 (Supporting Information). The result indicates that the OER activity of the FeNi-foil increased with an increase in temperature until 900 °C. NH3 gas being a rich source of N ensured the continuous interaction with FeNi-foil with increasing calcination time and can be adsorbed on it. The snapshots taken for the FeNi alloy foil before and after calcination show an apparent color change from silver to black. This physical change shown in the schematic illustration of the process indicated the formation of FeNi4.34 alloy NPs on the surface. The control experiments under an Ar atmosphere were performed to know the formation mechanism, which is presented in Figure S2 (Supporting Information). The results indicate that the FeNifoil OER performance does not increase under the Ar atmosphere even at high temperature (900 °C) for 3 h. This means that the Ar atmosphere is not favorable to increase the active sites on the surface of the foil; hence, low performance is observed. The OER performances of the samples calcined in NH3 and Ar atmosphere are shown in Figure S3 (Supporting Information). The XRD pattern of Ni-rich FeNi alloy NPs on the surface of FeNi-foil is shown in Figure 1. The XRD spectrum shows only three diffraction peaks originated from the face-centered cubic phase of FeNi alloy NPs. The diffraction peaks at 44.28°, 51.62°, and 75.82° corresponding to the (111), (200), and

Figure 2. (a) SEM images of FeNi-foil before calcination. (b, c) SEM and TEM images of FeNi4.34@FeNi-foil with lower to higher resolution, respectively. (d) HRTEM image of FeNi4.34 NPs. (e) Area selected for SEM mapping and (f, g) the corresponding mapping images for Fe and Ni in the FeNi4.34 NPs. C


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Figure 3. High-resolution XPS spectrum of (a, b) FeNi4.34@FeNi-foil of the Ni 2p and Ni 2p3/2 regions and (c, d) Fe 2P and Fe 2p3/2.

Figure 4. OER performance of as-prepared samples. (a) LSV curves for FeNi4.34@FeNi-foil, FeNi-foil, and IrO2 in alkaline (1 M KOH) solution. (b) Corresponding Tafel plots. (c) LSV curves obtained for the as-prepared FeNi4.34@FeNi electrode before and after 1000 cycles of the accelerated stability test. (d) Electrochemical impedance spectra of FeNi4.34@FeNi-foil, FeNi-foil, and IrO2 electrodes recorded at 1.55 V vs RHE.

mass spectrometry (ICP-MS) result (1:4.34) and slightly lower than the EDS elemental analysis (1:4.65). This final ratio is slightly different from the original ratio of pristine FeNi-foil, indicating the rearrangement of the Fe and Ni atoms on the surface during the high-temperature calcination process. The Ni 2p region spectrum (Figure 3a) shows the presence of Ni species in different states. The Ni 2p region can be deconvoluted to resolve the states of three components. Figure

3b shows a more clear view of the Ni 2p3/2 region. The peaks located around 852.7 and 855.8 eV can be assigned to metallic and Ni2+ (mainly NiO and Ni(OH)2), respectively. However, the peak at 861.3 eV can be assigned to the Ni satellite, which is also in good agreement with the previous literature.46−48 Figure 3c,d shows the Fe 2p region and a close view of the Fe 2p2/3 region, indicating the possible states of Fe. The survey spectrum of Fe 2p clearly shows the photoelectron peaks at D


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performance of OER. Previously reported research articles reveal that the presence of Ni in catalytic materials exhibits a characteristic redox peak at 1.39 V versus RHE, which is assigned for the conversion of Ni(II) to Ni(III).50 The presence of highly charged Fe(III) ions into the outer surface could retard the conversion of Ni(II) to Ni(III) and improve the stability of catalytic performance.51 On the basis of previous research findings, a detailed comparison of various highly active electrocatalysts for OER is shown in Table 1. Furthermore, Tafel plots derived from the LSV curves (Figure 4b) are used to investigate the OER catalytic kinetic performance of the samples and the slope values. The Tafel slope value of FeNi4.34@FeNi-foil (53 mV dec−1) is much lower than that of FeNi-foil (97 mV dec−1) and IrO2 (91 mV dec−1). The results are comparable with those of previously reported OER electrocatalysts (Table S4) that reveal its favorable reaction kinetics. Besides the higher OER performance, the asprepared FeNi4.34@FeNi electrode exhibits excellent stability in severe cyclic solutions, which is extremely desired for a dominating OER electrode. The stability test was successfully performed for 1000 potential cycles, as shown in Figure 4c. The LSV curve for the FeNi4.34@FeNi electrode was slightly down even after 1000 potential cycles, indicating its durability. This favorable durability of the FeNi4.34@FeNi electrode was achieved due to the strong interaction between FeNi4.34 NPs and the FeNi-foil. In addition, the electrode kinetics of the assynthesized catalysts in the OER process is also reviewed by electrochemical impedance spectroscopy (EIS) measurements at 1.55 V versus RHE, as shown in Figure 4d. The EIS spectra reveal that the charge transfer resistance (Rct) values of the catalysts increase in the order of FeNi4.34@ FeNi-foil (Rct, 3.2 Ω) < IrO2 (Rct, 4.6 Ω) < FeNi-foil (Rct, 10.4 Ω) and are inconsistent with the OER performances. The smaller charge transfer resistance of FeNi4.34@FeNi-foil than that of others indicates the faster electron transfer process during OER. The strong interaction of ultrasmall particles and the conductive FeNi-foil substrate is generated by the one-step growth process. It furnishes a highly efficient pathway for electron transport on the entire electrode and hence fast reaction kinetics. The electrochemically active surface area of the catalysts is evaluated by measuring the electrochemical double-layer capacitance (Cdl), which is directly proportional to the active sites of the catalyst.52 A simple cyclic voltammetry method53 was adopted to check the Cdl of the electrodes and to further explore the enhanced OER performance of the FeNi4.34@FeNifoil. Figure 5a,b reveals that the Cdl of FeNi4.34@FeNi-foil is

Table 1. Comparison of OER Performances of Different Non-Noble Metal-Based Electrocatalysts Tafel slope (mV dec−1)

η @ 10 mA cm−2 (mV)

FeNi4.34@FeNi

53

283

NiFe/CNx Fe−Ni−Ox/GC Fe-mCo3O4/GC FeNi/nanocarbon hybrids Ni−Co-oxide/Au-films Ni30Fe7Co20Ce43Ox/GC FeNi-LDH nanosheets LiCo0.33Ni0.33Fe0.33O2/GC Ni−Co oxide nanosheets α-Ni(OH)2/GC NiMo hollow nanorod

59 48 60 45 39 70 40 46 51 42 47

360 286 380 330 325 410 302 295 340 331 310

catalyst

ref this work 54 55 56 57 58 59 60 61 62 63 64

707.3, 712, 719.4, and 725.3 eV that can be attributed to the Fe 2p3/2 and Fe 2p1/2 regions. The Fe 2p region is deconvoluted to resolve each component. This confirmed the existence of zerovalent Fe0, oxidized Fe2+, and Fe3+ with a broad satellite peak.47,49 Our XPS results are comparable with the result of FeNi3-graphene nanocomposites, as discussed previously by Abellán et al., because the Ni-rich FeNi4.34 NPs behave in the same manner as FeNi3 NPs, which doubly confirms the formation of FeNi4.34@FeNi-foil successfully.47 The electrocatalytic oxygen evolution reaction (OER) activity of the as-prepared catalyst samples was investigated in an alkaline solution of 1 M potassium hydroxide (KOH). The as-prepared samples were directly used as a working electrode in a standard three-electrode system. The linear sweep voltammetry (LSV) polarization curves in Figure 4a correspond with FeNi4.34@FeNi-foil, FeNi-foil, and IrO2, in which the FeNi4.34@FeNi-foil as a working electrode exhibits better OER performance in comparison with other samples and remarkably reduced the overpotential from 412 to 283 mV to achieve a current density of 10 mA cm−2. However, FeNi-foil and IrO2 show weak OER performance as they require overpotentials of 412 and 314 mV, respectively, to afford a current density of 10 mA cm−2. This result clearly indicates that the fabrication of FeNi4.34@FeNi-foil is responsible for the enhancement of electrocatalytic OER performance. Being compared with the overpotentials of FeNi-foil (412 mV) and the as-prepared FeNi4.34@FeNi-foil (283 mV), it is proposed that the combination of better conductive substrate and material fabricated on it play an important role for the improved

Figure 5. (a) Cyclic voltammograms of FeNi4.34@FeNi-foil measured at different scan rates from 2 to 10 mV s−1 in 1 M KOH. (b) Plots of the corresponding current density at 1.11 V vs the scan rate. E


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(2) Yuan, C.; Wu, H. B.; Xie, Y.; Lou, X. W. D. Mixed TransitionMetal Oxides: Design, Synthesis, and Energy-Related Applications. Angew. Chem., Int. Ed. 2014, 53, 1488−1504. (3) Jiao, Y.; Zheng, Y.; Jaroniec, M.; Qiao, S. Z. Design of Electrocatalysts for Oxygen- and Hydrogen-Involving Energy Conversion Reactions. Chem. Soc. Rev. 2015, 44, 2060−2086. (4) Grimaud, A.; May, K. J.; Carlton, C. E.; Lee, Y.-L.; Risch, M.; Hong, W. T.; Zhou, J.; Shao-Horn, Y. Double Perovskites as a Family of Highly Active Catalysts for Oxygen Evolution in Alkaline Solution. Nat. Commun. 2013, 4, No. 2439. (5) Mao, S.; Wen, Z.; Huang, T.; Hou, Y.; Chen, J. High Performance Bifunctional Electrocatalysts of 3D Crumpled Graphene−Cobalt Oxide Nanohybrids for Oxygen Reduction and Evolution Reactions. Energy Environ. Sci. 2014, 7, 609−616. (6) 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. (7) Long, X.; Li, J.; Xiao, S.; Yan, K.; Wang, Z.; Chen, H.; Yang, S. A Strongly Coupled Graphene and FeNi Double Hydroxide Hybrid as an Excellent Electrocatalyst for the Oxygen Evolution Reaction. Angew. Chem., Int. Ed. 2014, 53, 7584−7588. (8) Louie, M. W.; Bell, A. T. An Investigation of Thin Film Ni−Fe Oxide Catalysts for the Electrochemical Evolution of Oxygen. J. Am. Chem. Soc. 2013, 135, 12329−12337. (9) Barnett, S. M.; Goldberg, K. I.; Mayer, J. M. A Soluble Copper− Bipyridine Water Oxidation Electrocatalyst. Nat. Chem. 2012, 4, 498− 502. (10) Symes, M. D.; Cronin, L. Decoupling Hydrogen and Oxygen Evolution During Electrolytic Water Splitting Using an ElectronCoupled-Proton Buffer. Nat. Chem. 2013, 5, 403−409. (11) Walter, M. G.; Warren, E. L.; McKone, J. R.; Boettcher, S. W.; Mi, Q.; Santori, E. A.; Lewis, N. S. Solar Water Splitting Cells. Chem. Rev. 2010, 110, 6446−6473. (12) Zeng, K.; Zhang, D. Recent Progress in Alkaline Water Electrolysis for Hydrogen Production and Applications. Prog. Energy Combust. Sci. 2010, 36, 307−326. (13) Bockris, J. O. M. Kinetics of Activation Controlled Consecutive Electrochemical Reactions: Anodic Evolution of Oxygen. J. Chem. Phys. 1956, 24, 817−827. (14) Wang, J.; Cui, W.; Liu, Q.; Xing, Z.; Asiri, A. M.; Sun, X. Recent Progress in Cobalt-Based Heterogeneous Catalysts for Electrochemical Water Splitting. Adv. Mater. 2016, 28, 215−230. (15) Song, F.; Hu, X. Exfoliation of Layered Double Hydroxides for Enhanced Oxygen Evolution Catalysis. Nat. Commun. 2014, 5, No. 4477. (16) McCrory, C. C. L.; Jung, S.; Peters, J. C.; Jaramillo, T. F. Benchmarking Heterogeneous Electrocatalysts for the Oxygen Evolution Reaction. J. Am. Chem. Soc. 2013, 135, 16977−16987. (17) Galán-Mascarós, J. R. Water Oxidation at Electrodes Modified with Earth-Abundant Transition-Metal Catalysts. ChemElectroChem 2015, 2, 37−50. (18) Lu, X.; Zhao, C. Electrodeposition of Hierarchically Structured Three Dimensional Nickel−Iron Electrodes for Efficient Oxygen Evolution at High Current Densities. Nat. Commun. 2015, 6, No. 6616. (19) Shan, Z.; Archana, P. S.; Shen, G.; Gupta, A.; Bakker, M. G.; Pan, S. NanoCOT: Low-Cost Nanostructured Electrode Containing Carbon, Oxygen, and Titanium for Efficient Oxygen Evolution Reaction. J. Am. Chem. Soc. 2015, 137, 11996−12005. (20) Long, X.; Li, G.; Wang, Z.; Zhu, H.; Zhang, T.; Xiao, S.; Guo, W.; Yang, S. Metallic Iron−Nickel Sulfide Ultrathin Nanosheets as a Highly Active Electrocatalyst for Hydrogen Evolution Reaction in Acidic Media. J. Am. Chem. Soc. 2015, 137, 11900−11903. (21) Liu, T.; Liu, Q.; Asiri, A. M.; Luo, Y.; Sun, X. An Amorphous CoSe Film Behaves as an Active and Stable Full Water-Splitting Electrocatalyst Under Strongly Alkaline Conditions. Chem. Commun. 2015, 51, 16683−16686. (22) Jin, H.; Wang, J.; Su, D.; Wei, Z.; Pang, Z.; Wang, Y. In Situ Cobalt−Cobalt Oxide/N-Doped Carbon Hybrids as Superior Bifunc-

high by calculating the slope from the linear relationship between the current density and the scan rate (Figure 5). The presence of a number of active sites on the catalyst shows higher OER catalytic performances. The improved OER electrocatalytic performance of FeNi4.34@FeNi-foil could be explained by means of (1) the morphology of NPs on the FeNi-foil that provides a large active surface area for reaction and (2) the interaction of FeNi4.34 NPs with highly conductive FeNi-foil enables fast electron transfer inside the electrocatalyst.

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CONCLUSIONS In summary, we demonstrated a simple, facile, and an effective route for the growth of bimetallic FeNi4.34 NPs embedded on the FeNi-foil substrate as an efficient OER electrode. The asprepared FeNi4.34@FeNi electrode shows high catalytic activity for OER in a strong basic medium (1 M KOH). The FeNi alloy-based catalyst exhibits a lower onset potential of 1.474 V and a low overpotential of 283 mV to achieve a current density of 10 mA cm−2 with a small Tafel slope of 53 mV dec−1. Ultrasmall FeNi particles could have a strong interaction with a highly conductive FeNi-foil substrate, which provides fast electron transport toward an efficient electrocatalytic OER and its stability. This work has potential to design inexpensive, durable, and efficient FeNi-based advanced electrodes for OER. This will open a new horizon toward the replacement of noble metal-based electrocatalysts for OER.

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ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.7b08922. Optimization conditions for OER electrocatalytic performance of samples prepared under ammonia and argon atmosphere; their comparison; size distribution; EDS spectra; XPS survey spectrum (Figures S1−S6) (PDF)

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected]. ORCID

Akif Zeb: 0000-0003-2188-6704 An-Wu Xu: 0000-0002-4950-0490 Author Contributions §

U.Y.Q. and C.-Z.Y. contributed equally to this work.

Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors acknowledge financial support from the Chinese Academy of Sciences (CAS), President’s International Fellowship Initiative (PIFI), the National Basic Research Program of China (2011CB933700), the National Natural Science Foundation of China (51572253, 21271165, and 21771171), and cooperation between NSFC and Netherland Organisation for Scientific Research (51561135011).

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REFERENCES

(1) Zhang, M.; de Respinis, M.; Frei, H. Time-Resolved Observations of Water Oxidation Intermediates on a Cobalt Oxide Nanoparticle Catalyst. Nat. Chem. 2014, 6, 362−367. F


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ACS Applied Materials & Interfaces tional Electrocatalysts for Hydrogen and Oxygen Evolution. J. Am. Chem. Soc. 2015, 137, 2688−2694. (23) Yan, Y.; Thia, L.; Xia, B. Y.; Ge, X.; Liu, Z.; Fisher, A.; Wang, X. Construction of Efficient 3D Gas Evolution Electrocatalyst for Hydrogen Evolution: Porous FeP Nanowire Arrays on Graphene Sheets. Adv. Sci. 2015, 2, No. 1500120. (24) Yan, Y.; Xia, B. Y.; Ge, X.; Liu, Z.; Fisher, A.; Wang, X. A Flexible Electrode Based on Iron Phosphide Nanotubes for Overall Water Splitting. Chem. − Eur. J. 2015, 21, 18062−18067. (25) Pickrahn, K. L.; Park, S. W.; Gorlin, Y.; Lee, H.-B.-R.; Jaramillo, T. F.; Bent, S. F. Active MnOx Electrocatalysts Prepared by Atomic Layer Deposition for Oxygen Evolution and Oxygen Reduction Reactions. Adv. Energy Mater. 2012, 2, 1269−1277. (26) Liu, Y.; Higgins, D. C.; Wu, J.; Fowler, M.; Chen, Z. Cubic Spinel Cobalt Oxide/Multi-Walled Carbon Nanotube Composites as an Efficient Bifunctional Electrocatalyst for Oxygen Reaction. Electrochem. Commun. 2013, 34, 125−129. (27) Yin, Q.; Tan, J. M.; Besson, C.; Geletii, Y. V.; Musaev, D. G.; Kuznetsov, A. E.; Luo, Z.; Hardcastle, K. I.; Hill, C. L. A Fast Soluble Carbon Free Molecular Water Oxidation Catalyst Based on Abundant Metals. Science 2010, 328, 342−345. (28) Liang, Y.; Li, Y.; Wang, H.; Zhou, J.; Wang, J.; Regier, T.; Dai, H. Co3O4 Nanocrystals on Graphene as a Synergistic Catalyst for Oxygen Reduction Reaction. Nat. Mater. 2011, 10, 780−786. (29) Lu, Z.; Wang, H.; Kong, D.; Yan, K.; Hsu, P.-C.; Zheng, G.; Yao, H.; Liang, Z.; Sun, X.; Cui, Y. Electrochemical Tuning of Layered Lithium Transition Metal Oxides for Improvement of Oxygen Evolution Reaction. Nat. Commun. 2014, 5, No. 4345. (30) Maiyalagan, T.; Jarvis, K. A.; Therese, S.; Ferreira, P. J.; Manthiram, A. Spinel-Type Lithium Cobalt Oxide as a Bifunctional Electrocatalyst for the Oxygen Evolution and Oxygen Reduction Reactions. Nat. Commun. 2014, 5, No. 3949. (31) Bockris, J. O.; Otagawa, T. Mechanism of Oxygen Evolution on Perovskites. J. Phys. Chem. 1983, 87, 2960−2971. (32) Suntivich, J.; May, K. J.; Gasteiger, H. A.; Goodenough, J. B.; Shao-Horn, Y. A Perovskite Oxide Optimized for Oxygen Evolution Catalysis from Molecular Orbital Principles. Science 2011, 334, 1383− 1385. (33) Landon, J.; Demeter, E.; Iṅ oğlu, N.; Keturakis, C.; Wachs, I. E.; Vasić, R.; Frenkel, A. I.; Kitchin, J. R. Spectroscopic Characterization of Mixed Fe−Ni Oxide Electrocatalysts for the Oxygen Evolution Reaction in Alkaline Electrolytes. ACS Catal. 2012, 2, 1793−1801. (34) Gong, M.; Li, Y.; Wang, H.; Liang, Y.; Wu, J. Z.; Zhou, J.; Wang, J.; Regier, T.; Wei, F.; Dai, H. An Advanced Ni−Fe Layered Double Hydroxide Electrocatalyst for Water Oxidation. J. Am. Chem. Soc. 2013, 135, 8452−8455. (35) 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. (36) Smith, A. M.; Trotochaud, L.; Burke, M. S.; Boettcher, S. W. Contributions to Activity Enhancement via Fe Incorporation in Ni(oxy) Hydroxide/Borate Catalysts for Near-Neutral pH Oxygen Evolution. Chem. Commun. 2015, 51, 5261−5263. (37) Yang, Y.; Zhuang, L.; Lin, R.; Li, M.; Xu, X.; Rufford, T. E.; Zhu, Z. A Facile Method to Synthesize Boron-Doped Ni/Fe Alloy NanoChains as Electrocatalyst for Water Oxidation. J. Power Sources 2017, 349, 68−74. (38) Liang, Y.; Liu, Q.; Asiri, A. M.; Sun, X.; He, Y. Nickel−Iron Foam as a Three-Dimensional Robust Oxygen Evolution Electrode with High Activity. Int. J. Hydrogen Energy 2015, 40, 13258−13263. (39) Zhao, Y.; Chen, S.; Sun, B.; Su, D.; Huang, X.; Liu, H.; Yan, Y.; Sun, K.; Wang, G. Graphene−Co3O4 Nanocomposite as Electrocatalyst with High Performance for Oxygen Evolution Reaction. Sci. Rep. 2015, 5, No. 7629. (40) Ma, T. Y.; Dai, S.; Jaroniec, M.; Qiao, S. Z. Metal−Organic Framework Derived Hybrid Co3O4−Carbon Porous Nanowire Arrays as Reversible Oxygen Evolution Electrodes. J. Am. Chem. Soc. 2014, 136, 13925−13931.

(41) Ganesan, P.; Sivanantham, A.; Shanmugam, S. Nanostructured Nickel−Cobalt−Titanium Alloy Grown on Titanium Substrate as Efficient Electrocatalyst for Alkaline Water Electrolysis. ACS Appl. Mater. Interfaces 2017, 9, 12416−12426. (42) Yeo, B. S.; Bell, A. T. Enhanced Activity of Gold-Supported Cobalt Oxide for the Electrochemical Evolution of Oxygen. J. Am. Chem. Soc. 2011, 133, 5587−5593. (43) Yuan, C.-Z.; Sun, Z.-T.; Jiang, Y.-F.; Yang, Z.-K.; Jiang, N.; Zhao, Z.-W.; Qazi, U. Y.; Zhang, W.-H.; Xu, A.-W. One-Step In Situ Growth of Iron−Nickel Sulfide Nanosheets on FeNi Alloy Foils: High Performance and Self-Supported Electrodes for Water Oxidation. Small 2017, No. 1604161. (44) Yu, Z.; Chen, D.; Rønning, M.; Vrålstad, T.; Ochoa-Fernández, E.; Holmen, A. Synthesis of Carbon Nanofibers on Ni−Fe−Al Hydrotalcite Derived catalysts: I. Preparation and Characterization of the Ni−Fe−Al Hydrotalcites and Their Derived Catalysts. Appl. Catal., A 2008, 338, 136−146. (45) Robinson, I.; Zacchini, S.; Tung, L. D.; Maenosono, S.; Thanh, N. T. K. Synthesis and Characterization of Magnetic Nanoalloys from Bimetallic Carbonyl Clusters. Chem. Mater. 2009, 21, 3021−3026. (46) Prieto, P.; Nistor, V.; Nouneh, K.; Oyama, M.; Abd-Lefdil, M.; Díaz, R. XPS Study of Silver, Nickel and Bimetallic Silver−Nickel Nanoparticles Prepared by Seed-Mediated Growth. Appl. Surf. Sci. 2012, 258, 8807−8813. (47) Abellán, G.; Prima-García, H.; Coronado, E. Graphene Enhances the Magnetoresistance of FeNi 3 Nanoparticles in Hierarchical FeNi3−Graphene Nanocomposites. J. Mater. Chem. C 2016, 4, 2252−2258. (48) Wang, X.; Liao, X.; Zhang, W.; Shi, B. Bio-Inspired Fabrication of Hierarchical Ni−Fe−P Coated Skin Collagen Fibers for HighPerformance Microwave Absorption. Phys. Chem. Chem. Phys. 2015, 17, 2113−2120. (49) 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. (50) Wang, H.; Casalongue, H. S.; Liang, Y.; Dai, H. Ni(OH)2 Nanoplates Grown on Graphene as Advanced Electrochemical Pseudocapacitor Materials. J. Am. Chem. Soc. 2010, 132, 7472−7477. (51) Lu, Z.; Xu, W.; Zhu, W.; Yang, Q.; Lei, X.; Liu, J.; Li, Y.; Sun, X.; Duan, X. Three-Dimensional NiFe Layered Double Hydroxide Film for High-Efficiency Oxygen Evolution Reaction. Chem. Commun. 2014, 50, 6479−6482. (52) 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. (53) Merki, D.; Vrubel, H.; Rovelli, L.; Fierro, S.; Hu, X. Fe, Co, and Ni Ions Promote the Catalytic Activity of Amorphous Molybdenum Sulfide Films for Hydrogen Evolution. Chem. Sci. 2012, 3, 2515−2525. (54) Ci, S.; Mao, S.; Hou, Y.; Cui, S.; Kim, H.; Ren, R.; Wen, Z.; Chen, J. Rational Design of Mesoporous NiFe-Alloy Based Hybrids for Oxygen Conversion Electrocatalysis. J. Mater. Chem. A 2015, 3, 7986− 7993. (55) Kuai, L.; Geng, J.; Chen, C.; Kan, E.; Liu, Y.; Wang, Q.; Geng, B. A Reliable Aerosol Spray Assisted Approach to Produce and Optimize Amorphous Metal Oxide Catalysts for Electrochemical Water Splitting. Angew. Chem., Int. Ed. 2014, 53, 7547−7551. (56) Xiao, C.; Lu, X.; Zhao, C. Unusual Synergistic Effects Upon Incorporation of Fe and/or Ni into Mesoporous Co3O4 for Enhanced Oxygen Evolution. Chem. Commun. 2014, 50, 10122−10125. (57) Zhang, X.; Xu, H.; Li, X.; Li, Y.; Yang, T.; Liang, Y. Facile Synthesis of Nickel−Iron/Nanocarbon Hybrids as Advanced Electrocatalysts for Efficient Water Splitting. ACS Catal. 2016, 6, 580−588. (58) Noel, N. K.; Abate, A.; Stranks, S. D.; Parrott, E. S.; Burlakov, V. M.; Goriely, A.; Snaith, H. J. Enhanced Photoluminescence and Solar Cell Performance via Lewis Base Passivation of Organic−Inorganic Lead Halide Perovskites. ACS Nano 2014, 8, 9815−9821. G


Research Article

ACS Applied Materials & Interfaces (59) Haber, J. A.; Cai, Y.; Jung, S.; Xiang, C.; Mitrovic, S.; Jin, J.; Bell, A. T.; Gregoire, J. M. Discovering Ce-Rich Oxygen Evolution Catalysts, from High Throughput Screening to Water Electrolysis. Energy Environ. Sci. 2014, 7, 682−688. (60) Song, F.; Hu, X. Exfoliation of Layered Double Hydroxides for Enhanced Oxygen Evolution Catalysis. Nat. Commun. 2014, 5, No. 4477. (61) Lu, Z.; Wang, H.; Kong, D.; Yan, K.; Hsu, P.-C.; Zheng, G.; Yao, H.; Liang, Z.; Sun, X.; Cui, Y. Electrochemical Tuning of Layered Lithium Transition Metal Oxides for Improvement of Oxygen Evolution Reaction. Nat. Commun. 2014, 5, No. 4345. (62) Wang, H.-Y.; Hsu, Y.-Y.; Chen, R.; Chan, T.-S.; Chen, H. M.; Liu, B. Ni3+-Induced Formation of Active NiOOH on the Spinel Ni− Co Oxide Surface for Efficient Oxygen Evolution Reaction. Adv. Energy Mater. 2015, 5, No. 1500091. (63) Gao, M.; Sheng, W.; Zhuang, Z.; Fang, Q.; Gu, S.; Yan, Y.; Jiang, J. Efficient Water Oxidation Using Nanostructured α-NickelHydroxide as an Electrocatalyst. J. Am. Chem. Soc. 2014, 136, 7077− 7084. (64) Tian, J.; Cheng, N.; Liu, Q.; Sun, X.; He, Y.; Asiri, A. M. SelfSupported NiMo Hollow Nanorod Array: An Efficient 3D Bifunctional Catalytic Electrode for Overall Water Splitting. J. Mater. Chem. A 2015, 3, 20056−20059.

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