CHEMSUSCHEM FULL PAPERS DOI: 10.1002/cssc.201402520
Hierarchically Superstructured Prussian Blue Analogues: Spontaneous Assembly Synthesis and Applications as Pseudocapacitive Materials Yanfeng Yue,[a] Zhiyong Zhang,[a] Andrew J. Binder,[b] Jihua Chen,[c] Xianbo Jin,[d] Steven H. Overbury,[a] and Sheng Dai*[a, b] Hierarchically superstructured Prussian blue analogues (hexacyanoferrate, M = NiII, CoII and CuII) are synthesized through a spontaneous assembly technique. In sharp contrast to macroporous-only Prussian blue analogues, the hierarchically superstructured porous Prussian blue materials are demonstrated to possess a high capacitance, which is similar to those of the
conventional hybrid graphene/MnO2 nanostructured textiles. Because sodium or potassium ions are involved in energy storage processes, more environmentally neutral electrolytes can be utilized, making the superstructured porous Prussian blue analogues a great contender for applications as high-performance pseudocapacitors.
Introduction Electrochemical capacitors are highly desirable energy storage devices due to their large powder density, long operating lifetimes, and ability to deliver high levels of electrical power. These advantages make them ideal for applications in the storage of energies generated by intermittent energy sources such as windmills and solar cells. The electric double-layer capacitor (EDLC) is the first kind of supercapacitor that can store charge electrostatically through a thin electron-ion separation layer within electrode/electrolyte interphases, e.g., carbon materials. For typical EDLCs, the capacitance is only between 15 and 50 mF cm2 in aqueous electrolytes and is even less in aprotic electrolytes. Another type of supercapacitor is a pseudocapacitor. Unlike an EDLC, a pseudocapacitor stores electrical energy Faradaically, either through a redox reaction in which the potential is a function of the activity ratio of the species in oxidation and reduction states, or through an underpotential deposition process that occupies electrode surface active sites progressively.[1] Because of the difference in their nature, a pseudo[a] Dr. Y. Yue, Dr. Z. Zhang, Dr. S. H. Overbury, Prof. Dr. S. Dai Chemical Sciences Division Oak Ridge National Laboratory Oak Ridge, Tennessee 37831 (USA) E-mail:
[email protected] [b] A. J. Binder, Prof. Dr. S. Dai Department of Chemistry University of Tennessee Knoxville, Tennessee 37996 (USA) [c] Dr. J. Chen Center for Nanophase Materials Science Division Oak Ridge National Laboratory Oak Ridge, TN 37831 (USA) [d] Dr. X. Jin College of Chemistry and Molecular Sciences Wuhan Univeristy Wuhan 430072 (PR China) Supporting Information for this article is available on the WWW under http://dx.doi.org/10.1002/cssc.201402520.
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
capacitor can usually yield a capacitance that is a factor of 100 higher than an EDLC with the same electrode surface. The most widely investigated electrode materials for redox pseudocapacitors are typically conductive polymers; microporous or mesoporous transition metal oxides such as RuO2,[2] IrO2,[3, 4] and MnO2,[5] ; and layered crystalline metal oxides like MoO3[6] and Nb2O5.[7] Among these materials, RuO2 has been considered to deliver the best performance, with both a high gravimetric pseudocapacitance and high electronic conductivity. However, because of the high price of ruthenium it is not feasible for widespread applications. Nanostructured transition metal oxides or hydroxides, such as NiO,[8] Ni(OH)2,[9, 10] and Co2O3,[11] have been considered low-cost alternatives with low toxicity and high theoretical capacitance. However, these materials suffer from low electronic conductivity and poor kinetic reversibility. In addition, a concern has been raised recently that although these materials demonstrate high “pseudocapacitance,” they are still battery materials in nature.[12] Liquid- or solid-solution-based redox systems have also been considered for pseudocapacitor applications.[1] However, little work has been carried out in this area. Prussian blue is a mixed-valent iron cyanide complex with a repeating unit of potassium or sodium ferrous ferricyanide hexacyano hexahydrate (A[FeIIIFeII(CN)6], A + = Na + or K + ). It has a cubic face-centered structure (space group symmetry Fm3¯m) with FeII and FeIII ions sitting on alternate corners of corner-shared octahedra bridged by small conjugated cyanide (CN) anions.[13] The unique properties in its structural arrangement allow compositional variation by combination with several transition metal ions in different oxidation states, such as CoII, CoIII, NiII, and CuII, which are called “Prussian blue analogues”. This metal substitution and variation lead to a combination of properties that are not readily found in other inorganic materials. Upon the insertion or extraction of alkaline cations, the reduction/oxidation of the FeIII/FeII occurs. More ChemSusChem 0000, 00, 1 – 8
&1&
These are not the final page numbers! ÞÞ
CHEMSUSCHEM FULL PAPERS important, unlike typical battery materials (NiO, TiS2, etc. .), which go through phase changes during charge/discharge,[14] cations can be reversibly inserted into or extracted from the Prussian blue open frame network without making a change in crystal structure or lattice parameters,[15, 16] indicating that no phase change has taken place at the electrode. In situ X-ray diffraction (XRD) measurement of a Prussian blue modified electrode also demonstrated that the inserted cations occupy the site randomly, forming a solid solution. The unique physical and electrochemical properties of Prussian blue and its analogues have led to their exploration as a new type of pseudocapacitive material. As charge transfer and ion diffusion are directly proportional to the surface area, the gravimetric capacitance and the energy and power densities of pseudocapacitors can be improved by designing high-surface-area porous electrodes. In this regard, attempts have been made during the past few years to discover new electrode materials and advanced nanostructured materials to increase specific capacitance, such as nanometer-sized Prussian blue analogues. Besides that, introducing extra porosity into the framework of Prussian blue analogues can further enhance their performance by providing large channels for facile ion mass transportation in the electrode. However, because of the instability of Prussian blue analogues in strong acids or bases, a hard or soft template method, usually employed in mesoporous material synthesis,[17] cannot be used in this case. Recently, an interesting templatefree stepwise “selective etching” method was introduced by Hu et al. by which they successfully prepared nanoporous Prussian blue analogues.[18] However, this method is unable to achieve stable mesopores. It is urgent that a new synthetic methodology be developed for the generation of mesoporosity in Prussian blue and its analogues. Recently, we developed a spontaneous assembly method— which can accurately control the coordination, nucleation, and nanoparticle aggregation—to construct mesopores in materials without any template or surfactant assistance (Scheme 1).[19] In this approach, two major requirements must
Scheme 1. Schematic illustration of superstructure formation in Prussian blue analogues with a nanoparticle spontaneous assembly mechanism.
be fulfilled: (1) uniform nanometer-sized building units must be generated without any large single crystals, and (2) the mesopores generated from nanocrystal aggregation cannot be lost through re-dissolution in the solvent.[20] To meet these requirements, ligands were added in the metal ion precursor so 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org lution under vigorous stirring to facilitate the rapid, thorough generation of uniformly dispersed nanocrystals and to avoid their further growth into larger single crystals. In the meantime, the solvent was carefully chosen for its capability to act as an agent for local crystallinity without readily dissolving the desired coordination complex. In this work, we fabricated a series hierarchical superstructured Prussian blue analogues based on this spontaneous assembly technique, called “mesoMHCFs” (hexacyanoferrate, M = NiII, CoII or CuII). In contrast, macroporous-only Prussian blue analogue, named as macroMHCF, obtained by a solvothermal method without any perturbation, was demonstrated with a low surface area due to the existence of textural packing the large particles. Further electrochemical characterizations indicate that the hierarchically porous structure is of significance in improving the capacitance of Prussian blue-based materials: with the assistance of mesopores, the mesoMHCFs demonstrated a capacitance over one order of magnitude higher compared to macroporousonly Prussian blue analogue.
Results and Discussion The as-synthesized mesoMHCF series were crystalline and were found to have an XRD spectrum corresponding to a phasepure face-centered cubic structure (Figure S1 in the Supporting Information).[16, 21] The broad peaks observed by XRD confirm the formation of small crystallites[22] with calculated crystallite sizes of 11, 12, and 16 nm for mesoNiHCF, mesoCoHCF, and mesoCuHCF, respectively. The biggest crystallites, 16 nm, were observed for mesoCuHCF, indicating a higher degree of periodicity and crystallinity under the same reaction time. The mesoMHCF series were also characterized by FTIR spectroscopy, and the FTIR spectra presented a band in the range of 2,070– 2,090 cm1, characteristic of the CN stretching mode (mesoNiHCF: 2,084 cm1; mesoCoHCF: 2080 cm1; CuHCF: 2078 cm1) (Figure S2, Supporting Information).[23] Compared with the initial potassium hexacyanometallate (IR band at 2046 cm1), the CN stretch band was shifted to a higher frequency as a result of the FeCNM coordination. The molar Fe/M ratios of the mesoMHCF series were obtained by inductively coupled plasma (ICP) analysis; and the molar ratios were calculated to be 1.02:1.00 (Ni/Fe), 1.06:1.00 (Co/Fe), and 0.86:1.00 (Cu/Fe) for mesoNiHCF, mesoNiHCF, and mesoCuHCF, respectively. The macroporous NiHCF prepared by the solvothermal method was named as macroNiHCF, and was also characterized by powder XRD (Figure S3, Supporting Information), and ICP analysis (with the molar ratio of Ni/Fe being 0.96:1.00). The mesoporous superstructures of the mesoMHCF series were demonstrated by SEM and TEM (Figure 1). As observed in the SEM images (Figure 1 a, c, e), continuous networks of these materials are formed, with some aggregates clearly observed. The mesoporous pores are confirmed by HRTEM images (Figure 1 b, d, f), which correspond to the aggregation of nanometer-sized particles with pore sizes falling in the range of 3– 45 nm (mesoNiHCF), 3–30 nm (mesoCoHCF), and 3–25 nm (mesoCuHCF), respectively. ChemSusChem 0000, 00, 1 – 8
&2&
These are not the final page numbers! ÞÞ
CHEMSUSCHEM FULL PAPERS
Figure 1. SEM images (a, c, e) and high-magnification TEM images (b, d, f) of mesoNiHCF (top), mesoCoHCF (middle), and mesoCuHCF (bottom).
To further check the interconnected pores in these materials and to determine the surface areas, nitrogen adsorption–desorption isotherms and Barrett–Joyner–Halenda (BJH) pore size distribution plots are shown in Figure 2. Before the gas sorption measurements, lattice guest molecules were removed by solvent exchange, followed by thermal activation at 150 8C under flowing N2. The isotherms can be classified as H2-type hysteresis loops characteristic of large constricted mesopores. The Brunauer–Emmett–Teller (BET) surface areas are 243, 254, and 163 m2 g1 for mesoNiHCF, mesoCoHCF, and mesoCuHCF, respectively (Table S1, Supporting Information). On the basis of the pore size distribution plots, distinct maxima centered at approximately 30, 16, and 10 nm can be observed for mesoNiHCF, mesoCoHCF, and mesoCuHCF, respectively. These are consistent with the observations of the SEM and HRTEM images (Figure 1). The differences in surface areas and pore size distributions of these materials may be attributed to the different nanoparticle sizes, interparticle spacing and internal voids. In the case of macroNiHCF, the textural macropores were observed in the SEM and HRTEM images (Figure 3), which formed by packing of the well crystalline single-grained particles. The observations are consistent with the changes in the pore size distribution (Figure S4 and Table S1, Supporting Information) and increased powder XRD peak intensities (Figure S3, Supporting Information). 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org
Figure 2. N2 196 8C isotherms of the mesoMHCF series (a) and corresponding BJH pore-size distribution (PSD) curves (b).
Figure 3. SEM (a) and TEM (b) images of macroNiHCF.
To investigate the electrochemical properties of these hierarchical porous Prussian blue analogues and their potential application in energy storage, cyclic voltammetries (CVs) were carried out in 1.0 m Na2SO4 at varying sweep rates. The working electrode was prepared with an active material loading of 0.5 mg cm2, and 20 wt % of low-capacitance onion-like carbons (25 F g1) was mixed to increase the conductivity.[24, 25] Serving as a control sample, the solvothermal synthesized macroNiHCF, which contains only macropores, was also examined and compared with the mesoMHCFs. Unlike widely studied transition-metal oxides or hydroxide capacitors, whose redox reactions are pH dependent and mostly take place in alkaline electrolyte, Prussian blue analogues store and release charge through redox reaction between the ferrous and ferric ChemSusChem 0000, 00, 1 – 8
&3&
These are not the final page numbers! ÞÞ
CHEMSUSCHEM FULL PAPERS oxidation states in the Fe center.[26] They are coupled by the reversible insertion/extraction of alkali cation (Na + ). Therefore, they can be used with more environmentally friendly neutral electrolytes. In this process, the overall reaction can be described as follows: NaMII ½FeIII ðCNÞ6 þ Naþ þ e Ð Na2 MII ½FeII ðCNÞ6 However, unlike in the study of Na-ion battery in which the charge/discharge rate was slow,[19] here we demonstrated that these mesoporous materials can also undergo a very high-rate insertion/extraction of ions, endowing them the same pseudocapacitive character as that found in some other materials such as TiS2 and MoS2. Typical CVs of these mesoMHCFs are shown in Figure 4 a. Whereas battery materials usually exhibit
Figure 4. CVs of mesoMHCF series and macroNiHCF in 1.0 m Na2SO4 with a scan rate of 5 mV s1 (a) and specific capacitance derived from CVs at different scan rates (b).
irreversibility between anodic and cathodic scans, reversible pseudocapacitive behavior was presented on all three mesoMHCFs, with a separation (DEp) between the oxidation and reduction peaks of around 30 mV. This indicates that facile cation transfer was achieved on the as-prepared materials, owing to the large mesopore channels. A comparison of the CVs obtained on these three materials indicates that meso 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org NiHCF and mesoCuHCF go through similar single redox reactions, with Em = (Ep,a + Ep,c)/2 at 0.39 and 0.60 V, respectively. However, in the case of mesoCoHCF, three continuous redox pairs were shown in the full scan range from 0.2 to 1.0 V, indicating a larger operating voltage window can be applied to this material. The CV profile of macroNiHCF is also shown in Figure 4 a, which presents a pair of broad humps with a very low current density, compared to that of mesoNiHCF. This indicates the lack of mesopores has strongly limited the intercalation of cation inside the macroNiHCF and only allows the reaction to occur on/near the surface of big crystals. Owing to the benefit of mesopores, the specific capacitances derived from the CVs (Figure 4 a) are 184, 243, and 295 F g1 at 5 mV s1 for mesoNiHCF, mesoCuHCF, and mesoCoHCF, respectively (Table S1, Supporting Information), which are 10–16 times higher than that of macroNiHCF (18 F g1). As the theoretical capacitance of CoHCF in a 0.8 V voltage window is 410 F g1, the value obtained in this case indicated that over 70 % of the mesoCoHCF is electrochemically active in this system. Note also that this value (295 F g1 on mesoCoHCF) is comparable to that obtained on hybrid graphene/MnO2 nanostructured textiles ( 275 F g1 at 5 mV s1),[27] indicating the as-prepared metal hexacyanoferrates have a potential application as highperformance pseudocapacitive materials. The rate-dependent performance was investigated by increasing the scan rate up to 200 mV s1. Upon the increase in scan rate, the Faradaic charge storages/releases were delayed by the relatively slow cation diffusion, resulting in large DEp values (Figure S5, Supporting Information) and a drop in capacitance (Figure 4 b). At the scan rate of 200 mV s1, the observed capacitances of mesoNiHCF, mesoCuHCF, and mesoCoHCF still remain 85 %, 62 %, and 50 % of their original values, respectively, better than those of layered MnO2[28] and even mesoporous carbons.[29] The pseudocapacitive performances of these mesoMHCFs were further investigated by a log(i)log(u) plot (Figure S6 a, Supporting Information). Generally, the relationship of current i and sweep rate u can be described as i = aub. For an ideal pseudocapacitor, b is approximately 1 whereas for battery materials b is usually 0.5. As shown in Figure S4 a in the Supporting Information, the b values obtained on all three of these catalysts are between 0.7 and 0.9, indicating these materials display typical pseudocapacitive behavior. The performance of these pseudocapacitive materials was also studied by galvanostatic charge/discharge at 1.0 A g1 between 0.2 to 1.0 V versus saturated calomel electrode (SCE). The voltage–time profile (Figure S7 a, Supporting Information) shows symmetric characteristics on all these three materials, indicating a good pseudocapacitive behavior of this type of Prussian Blue analogue. The capacitance calculated from the discharge curve are 194, 200, and 314 F g1 for mesoNiHCF, mesoCuHCF, and mesoCoHCF, which is consistent with the value obtained derived from CV curves. The cyclic stability was analyzed by galvanostatic charge/discharge at the same condition over 100 cycles. As shown in Figure 5 a, capacitance losses were observed for all materials, probably because of the fast cation migration gradually destroying the crystal structure of these mesoporous Prussian blue analogues. ChemSusChem 0000, 00, 1 – 8
&4&
These are not the final page numbers! ÞÞ
CHEMSUSCHEM FULL PAPERS
Figure 5. Normalized specific activities derived from galvanostatic charge/ discharge at a high current density of 1.0 A g1 in (a) 1.0 m Na2SO4 and (b) 1.0 m NaClO4 in MeCN.
The mesoMHCFs were further investigated in acetonitrile (MeCN), with 1.0 m NaClO4 as the electrolyte from 0.1 to 1.2 V vs. SCE. To avoid the swollen Nafion ionomer in MeCN, PVDF (polyvinylidene fluoride) was used as the binder. The electrochemical behaviors of these materials in MeCN are similar to those in an aqueous electrolyte (Figure 6). However, the peak width and DEp in MeCN both indicate a high activation energy was required for Na + to transfer though the organic electrolyte/solid interphase (Figure S8, Supporting Information).[30] The specific capacitances calculated from the CV profile are 149, 190, and 169 F g1 for mesoNiHCF, mesoCuHCF, and mesoCoHCF, respectively (Table S1, Supporting Information). Because of the higher activation energy for interphase charge transfer between the electrode and the MeCN electrolyte, larger capacitance drops were observed on all these catalysts at higher scan rates. For example, at a scan rate of 200 mV s1, mesoCoHCF retains only approximately 50 % of its original capacitance. In the meantime, the b value in the log(i)log(u) plot also decreased slightly to 0.6–0.7 for these three materials (Figure S6 b, Supporting Information). The specific capacitances calculated from the voltage–time profile (Figure S7 b, Supporting Information) are 134, 163, and 142 F g1 for mesoNiHCF, mesoCuHCF, and mesoCoHCF at 1.0 A g1. Compared with the aqueous electrolyte, mesoMHCF series in MeCN have a lower 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org
Figure 6. CVs of mesoMHCF series in 1.0 m NaClO4 MeCN solution (a) and specific capacitance derived from CVs at different scan rates (b).
capacity for salt dissolution in most cases, probably due to some hydratization of the materials. Therefore, it is considered to be friendly to these ionic bond-based Prussian blue analogues. As shown in Figure 6 b, the cyclic stabilities of these mesoMHCFs significantly improved under the same testing conditions. After 1000 charge/discharge cycles at 1.0 A g1, mesoNiHCF lost only 5 % of its original capacitance. The mesoCoHCF and mesoCuHCF also kept ~ 80 % of their initial value.
Conclusions A simple spontaneous assembly method for synthesizing hierarchical superstructured Prussian blue analogues, mesoMHCF, has been presented. These materials, exhibiting a capacitance comparable to that of conventional hybrid graphene/MnO2 nanostructured textiles, possess the advantage of being suited for use with more environmentally neutral electrolytes, making mesoMHCF a candidate for applications as pseudocapacitive materials. The simple, low-cost, template-free technique outlined in this paper has important implications for the fabrication of meso/macroporous materials, especially for materials unsuitable for hard or soft templating fabrication. ChemSusChem 0000, 00, 1 – 8
&5&
These are not the final page numbers! ÞÞ
CHEMSUSCHEM FULL PAPERS
www.chemsuschem.org
Experimental Section
was sponsored at Oak Ridge National Laboratory by the Division of Scientific User Facilities, Office of Basic Energy Sciences, U.S. Department of Energy.
Materials Preparation and Characterization A typical procedure to prepare mesoNiHCF: A solution of nickel(II) acetate tetrahydrate (0.249 g, 1 mmol) in 17.5 mL water and 2.5 mL dimethylformamide (DMF) was added to a solution of sodium hexacyanoferrate(II) decahydrate (0.484 g, 1 mmol) and 0.7 g NaCl in 17.5 mL water and 2.5 mL DMF under stirring. The mixture was stirred at room temperature for 4 h, and the resulting precipitate was separated by centrifugation and subsequently washed with water and methanol. The resulting product was dried under vacuum at 60 8C overnight before FT–IR spectroscopy, ICP analysis, powder XRD, SEM, TEM, nitrogen adsorption-desorption measurements, and electrochemical characterization. The mesoCoHCF and mesoCuHCF were prepared similarly to mesoNiHCF, but using cobalt(II) acetate tetrahydrate or copper(II) acetate monohydrate instead of nickel(II) acetate tetrahydrate. The products were called mesoMHCF, where M = NiII, CoII, or CuII.
Solvothermal method for the preparation of macroNiHCF Nickel(II) acetate tetrahydrate (0.249 g, 1 mmol) in 10.5 mL water and 1.5 mL DMF was added to a solution of sodium hexacyanoferrate(II) decahydrate (0.484 g, 1 mmol) in 10.5 mL water and 1.5 mL DMF. The mixture was heated to 150 8C in an autoclave and kept at this temperature for 72 h; the resulting precipitate was separated by centrifugation and subsequently washed with water and methanol. The resulting product was named as macroNiCHF, and dried under vacuum at 60 8C overnight before ICP, powder XRD, SEM, TEM, nitrogen adsorption-desorption measurements, and electrochemical characterization.
Electrochemical Characterization For the electrochemical experiments, 5.0 mg of the as-prepared mesoMHCF material, 1.0 mg of onion-like carbon, and 7.5 mL 5 wt % Nafion solution were first mixed in 1.0 mL of isopropanol. In the case of macroNiHCF, 10.0 mg of the active material was mixed with 1.0 mg of onion-like carbon, 7.5 mL 5 wt % Nafion solution and 1.0 mL of isopropanol. 20 mL of obtained ink was then dropcasted on a well-polished glassy carbon electrode to yield the working electrode. CVs were carried out in 1.0 m Na2SO4 from 0.2 to 1.0 V vs. SCE at different scan rates. The specific capacitance (Cg) was calculated from the CV curve following Equation (1): R Csp ¼
iðEÞdE 2DEmu
ð1Þ
where Csp is the specific capacitance of an individual sample, i(E) is the instantaneous current, si(E)dE the total voltammetric charge obtained by integration of positive and negative polarizations in a cyclic voltammogram, DE is the potential window width, m is the mass of the sample in the electrode, and u is the scan rate.
Acknowledgements The work was supported as part of the Fluid Interface Reactions, Structures, and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. TEM experiments were conducted at the Center for Nanophase Materials Sciences, which 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Keywords: hierarchical superstructures · prussian blue · prussian blue analogues · pseudocapacitive materials · spontaneous assembly [1] a) J. Chen, K. Huang, S. Liu, X. Hu, J. Power Sources 2009, 186, 565 – 569; b) F. Zhao, Y. Wang, X. Xu, Y. Liu, R. Song, G. Lu, Y. Li, ACS Appl. Mater. Interfaces 2014, 6, 11007 – 11012; c) N. Maiti, J. Lim, K. E. Lee, W. J. Lee, S. O. Kim, Adv. Mater. 2014, 26, 615 – 619; d) Q. Lu, J. G. Chen, J. Q. Xiao, Angew. Chem. Int. Ed. 2013, 52, 1882 – 1889; Angew. Chem. 2013, 125, 1932 – 1940; e) B. E. Conway, V. Birss, J. Wojtowicz, J. Power Sources 1997, 66, 1 – 14; f) M.-K. Song, S. Cheng, H. Chen, W. Qin, K.-W. Nam, S. Xu, X.-Q. Yang, A. Bongiorno, J. Lee, J. Bai, T. A. Tyson, J. Cho, M. Liu, Nano Lett. 2012, 12, 3483 – 3490; g) Y. Liang, M. G. Schwab, L. Zhi, E. Mugnaioli, U. Kolb, X. Feng, K. Mllen, J. Am. Chem. Soc. 2010, 132, 15030 – 15037; h) T. Chen, Y. Xue, A. K. Roy, L. Dai, ACS Nano 2014, 8, 1039 – 1046; i) S.-K. Kim, Y. K. Kim, H. Lee, S. B. Lee, H. S. Park, ChemSusChem 2014, 7, 1094 – 1101. [2] a) Y.-S. Hu, Y.-G. Guo, W. Sigle, S. Hore, P. Balaya, J. Maier, Nat. Mater. 2006, 5, 713 – 717; b) V. Birss, R. Myers, H. Angerstein-Kozlowska, B. E. Conway, J. Electrochem. Soc. 1984, 131, 1502 – 1510. [3] J. Mozota, B. E. Conway, Electrochim. Acta 1983, 28, 1 – 8. [4] B. E. Conway, J. Mozota, Electrochim. Acta 1983, 28, 9 – 16. [5] a) H. Y. Lee, V. Manivannan, J. B. Goodenough, Comptes Rendus de L’Acadmie des Sciences—Series IIC—Chemistry 1999, 2, 565 – 577; b) Y.-H. Lin, T.-Y. Wei, H.-C. Chien, S.-Y. Lu, Adv. Energy Mater. 2011, 1, 901 – 907. [6] T. Brezesinski, J. Wang, S. H. Tolbert, B. Dunn, Nat. Mater. 2010, 9, 146 – 151. [7] a) Y. Ren, Z. Ma, P. G. Bruce, Chem. Soc. Rev. 2012, 41, 4909 – 4927; b) K. Brezesinski, J. Wang, J. Haetge, C. Reitz, S. O. Steinmueller, S. H. Tolbert, B. M. Smarsly, B. Dunn, T. Brezesinski, J. Am. Chem. Soc. 2010, 132, 6982 – 6990; c) J. W. Kim, V. Augustyn, B. Dunn, Adv. Energy Mater. 2012, 2, 141 – 148. [8] a) J.-H. Kim, K. Zhu, Y. Yan, C. L. Perkins, A. J. Frank, Nano Lett. 2010, 10, 4099 – 4104; b) C. Wu, X. Lu, L. Peng, K. Xu, X. Peng, J. Huang, G. Yu, Y. Xie, Nat. Commun. 2013, 4, 2431; c) H. B. Li, M. H. Yu, F. X. Wang, P. Liu, Y. Liang, J. Xiao, C. X. Wang, Y. X. Tong, G. W. Yang, Nat. Commun. 2013, 4, 1894. [9] H. Wang, H. S. Casalongue, Y. Liang, H. Dai, J. Am. Chem. Soc. 2010, 132, 7472 – 7477. [10] Y. Jiang, P. Wang, X. Zang, Y. Yang, A. Kozinda, L. Lin, Nano Lett. 2013, 13, 3524 – 3530. [11] S. K. Meher, G. R. Rao, J. Phys. Chem. C 2011, 115, 15646 – 15654. [12] P. Simon, Y. Gogotsi, B. Dunn, Science 2014, 343, 1210 – 1211. [13] a) H. J. Buser, A. Ludi, W. Petter, D. Schwarzenbach, J. Chem. Soc. Chem. Commun. 1972, 1299 – 1299; b) K. Itaya, I. Uchida, V. D. Neff, Acc. Chem. Res. 1986, 19, 162 – 168; c) S. Margadonna, K. Prassides, A. N. Fitch, Angew. Chem. Int. Ed. 2004, 43, 6316 – 6319; Angew. Chem. 2004, 116, 6476 – 6479; d) A. Ludi, H.-U. Gdel, M. Regg, Inorg. Chem. 1970, 9, 2224 – 2227; e) T. Matsuda, J. Kim, Y. Moritomo, J. Am. Chem. Soc. 2010, 132, 12206 – 12207; f) H. J. Buser, D. Schwarzenbach, W. Petter, A. Ludi, Inorg. Chem. 1977, 16, 2704 – 2710; g) Y. Yang, C. Brownell, N. Sadrieh, J. May, A. Del Grosso, D. Place, E. Leutzinger, E. Duffy, R. He, F. Houn, R. Lyon, P. Faustion, Clin. Toxicol. 2007, 45, 776 – 781. [14] a) B. E. Conway, J. Electrochem. Soc. 1991, 138, 1539 – 1548; b) H. Pan, Y.S. Hu, L. Chen, Energy Environ. Sci. 2013, 6, 2338 – 2360. [15] D. Ellis, M. Eckhoff, V. D. Neff, J. Phys. Chem. 1981, 85, 1225 – 1231. [16] T. Ikeshoji, T. Iwasaki, Inorg. Chem. 1988, 27, 1123 – 1124. [17] a) Y. Shi, Y. Wan, D. Zhao, Chem. Soc. Rev. 2011, 40, 3854 – 3878; b) F. Brub, A. Khadhraoui, M. T. Janicke, F. Kleitz, S. Kaliaguine, Ind. Eng. Chem. Res. 2010, 49, 6977 – 6985; c) D. Carriazo, M. C. Serrano, M. C. Gutirrez, M. L. Ferrer, F. del Monte, Chem. Soc. Rev. 2012, 41, 4996 – 5014. [18] M. Hu, J.-S. Jiang, Y. Zeng, Chem. Commun. 2010, 46, 1133 – 1135. [19] Y. Yue, Z.-A. Qiao, P. F. Fulvio, A. J. Binder, C. Tian, J. Chen, K. M. Nelson, X. Zhu, S. Dai, J. Am. Chem. Soc. 2013, 135, 9572 – 9575.
ChemSusChem 0000, 00, 1 – 8
&6&
These are not the final page numbers! ÞÞ
CHEMSUSCHEM FULL PAPERS [20] Y. Yue, A. J. Binder, B. Guo, Z. Zhang, Z.-A. Qiao, C. Tian, S. Dai, Angew. Chem. Int. Ed. 2014, 53, 3134 – 3137; Angew. Chem. 2014, 126, 3198 – 3201. [21] a) L. Wang, Y. Lu, J. Liu, M. Xu, J. Cheng, D. Zhang, J. B. Goodenough, Angew. Chem. Int. Ed. 2013, 52, 1964 – 1967; Angew. Chem. 2013, 125, 2018 – 2021; b) X. Wu, Y. Cao, X. Ai, J. Qian, H. Yang, Electrochem. Commun. 2013, 31, 145 – 148; c) Y. Mizuno, M. Okubo, E. Hosono, T. Kudo, K. Oh-ishi, A. Okazawa, N. Kojima, R. Kurono, S. Nishimura, A. Yamada, J. Mater. Chem. A 2013, 1, 13055 – 13059. [22] C. D. Wessells, S. V. Peddada, R. A. Huggins, Y. Cui, Nano Lett. 2011, 11, 5421 – 5425. [23] P. J. Kulesza, M. A. Malik, A. Denca, J. Strojek, Anal. Chem. 1996, 68, 2442 – 2446. [24] D. Pech, M. Brunet, H. Durou, P. H. Huang, V. Mochalin, Y. Gogotsi, P. L. Taberna, P. Simon, Nat. Nanotechnol. 2010, 5, 651 – 654. [25] D. M. Anjos, J. K. McDonough, E. Perre, G. M. Brown, S. H. Overbury, Y. Gogotsi, V. Presser, Nano Energy 2013, 2, 702 – 712.
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemsuschem.org [26] a) Y. You, X.-L. Wu, Y.-X. Yin, Y.-G. Guo, J. Mater. Chem. A 2013, 1, 14061 – 14065; b) Y. Lu, L. Wang, J. Cheng, J. B. Goodenough, Chem. Commun. 2012, 48, 6544 – 6546; c) N. Imanishi, T. Morikawa, J. Kondo, R. Yamane, Y. Takeda, O. Yamamoto, H. Sakaebe, M. Tabuchi, J. Power Sources 1999, 81 – 82, 530 – 534. [27] G. Yu, L. Hu, M. Vosgueritchian, H. Wang, X. Xie, J. R. McDonough, X. Cui, Y. Cui, Z. Bao, Nano Lett. 2011, 11, 2905 – 2911. [28] M. Yeager, W. X. Du, R. Si, D. Su, N. Marinkovic, X. W. Teng, J. Phys. Chem. C 2012, 116, 20173 – 20181. [29] P. F. Fulvio, P. C. Hillesheim, Y. Oyola, S. M. Mahurin, G. M. Veith, S. Dai, Chem. Commun. 2013, 49, 7289 – 7291. [30] Y. Mizuno, M. Okubo, E. Hosono, T. Kudo, H. Zhou, K. Oh-ishi, J. Phys. Chem. C 2013, 117, 10877 – 10882. Received: June 7, 2014 Revised: September 27, 2014 Published online on && &&, 0000
ChemSusChem 0000, 00, 1 – 8
&7&
These are not the final page numbers! ÞÞ
FULL PAPERS Y. Yue, Z. Zhang, A. J. Binder, J. Chen, X. Jin, S. H. Overbury, S. Dai* && – && Hierarchically Superstructured Prussian Blue Analogues: Spontaneous Assembly Synthesis and Applications as Pseudocapacitive Materials
2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Analogue is back! Hierarchically superstructured Prussian blue analogues were fabricated through a spontaneous assembly technique. These Prussian blue analogues, showing capacitance comparable with conventional hybrid graphene/MnO2 nanostructured textiles, possess the advantage that they can be used with more environmentally neutral electrolytes, making Prussian blue analogues a great contender for applications as pseudocapacitive materials.
ChemSusChem 0000, 00, 1 – 8
&8&
These are not the final page numbers! ÞÞ