Ni2P2O7 Nanoarrays with Decorated C3N4 Nanosheets as Efficient

Subscriber access provided by Kaohsiung Medical University

Article

Ni2P2O7 Nanoarrays with Decorated C3N4 Nanosheets as Efficient Electrode for Supercapacitors Ning Zhang, Chen Chen, Yule Chen, Gen Chen, Chengan Liao, Bo Liang, Jisheng Zhang, An Li, Baopeng Yang, Zhihe Zheng, Xiaohe Liu, Anqiang Pan, Shuquan Liang, and Renzhi Ma ACS Appl. Energy Mater., Just Accepted Manuscript • DOI: 10.1021/acsaem.8b00114 • Publication Date (Web): 30 Apr 2018 Downloaded from http://pubs.acs.org on May 3, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Applied Energy Materials

Ni2P2O7

Nanoarrays

Nanosheets

as

with

Decorated

Efficient

Electrode

C3N4 for

Supercapacitors Ning Zhang,*, † Chen Chen,† Yule Chen,† Gen Chen,† Chengan Liao,† Bo Liang,† Jisheng Zhang,† An Li,† Baopeng Yang,† Zhihe Zheng,† Xiaohe Liu,*,† Anqiang Pan,† Shuquan Liang,† and Renzhi Ma*, ‡ †

School of Materials Science and Engineering, Central South University, Changsha, Hunan

410083, China ‡

International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials

Science (NIMS), 1−1 Namiki, Tsukuba, Ibaraki 305−0044, Japan

KEYWORDS Supercapacitor, Nickel pyrophosphate, C3N4, Electrochemistry, Electrode ABSTRACT Ni2P2O7 based composites grown on conductive substrate can efficiently promote the electrical transport during the electrochemical reactions in supercapacitors. However, Ni2P2O7 nanoarrays are easily peeled off from the substrate upon repeated electrochemical reaction. Herein, Ni2P2O7

ACS Paragon Plus Environment

ACS Applied Energy Materials 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

nanoarrays grown on Ni foam with surficial decorated C3N4 thin nanosheets are achieved by a hydrothermal and in situ calcination strategy. The decorated C3N4 nanosheet network on the surface fully covers both Ni2P2O7 and Ni foam and efficiently prevent Ni2P2O7 nanoarrays from peeling off during the charge and discharge cycles. The optimized composites exhibit high pseudocapacitance and greatly enhanced cycling stability. The assembled asymmetric supercapacitor shows favorable specific capacitance and stability as energy storage devices. Such a strategy for fabricating C3N4 modified Ni2P2O7 nanoarrays is feasible and efficient, and can be therefore extended for constructing other electrodes with high capacitance and excellent stability. INTRODUCTION Developing environmentally friendly methods for converting and storing energy is important to solve the energy outrage and polluted environment.1–3 Electrochemical power storage devices including supercapacitors (SCs) and batteries now have been attracted intensive research interest.4–6 As a result of high power density with fast charging and discharging cycles, SCs have been studied extensively as promising power storage devices.7–10 Over the past years, great progress has been achieved in developing electrochemical active materials as electrodes in SCs including carboneous materials,8,9,11 polymers,12,13 inorganic metal componds,14–16 and metal−organic frameworks.2,17,18 Among them, transition metal polyphosphates, such as Ni2P2O7, CoP2O7, and Mn2P2O7, are of considerable interest due to their outstanding properties as electrodes in supercapacitor.19–21 In comparison with phosphates, the polyphosphates possess better chemical stability, which is beneficial for the long-term cycling ability.22,23 However, the poor conductivity of the polyphosphates renders slow transport kinetics of charge carrier and low specific capacitance.22 To promote the electrical transport, coupling transition metal polyphosphates with conductive materials such as carbon fiber, Ni foam, yarn mesh and so on


Page 2 of 25

Page 3 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


can improve the overall conductivity of composites.24,25 Unfortunately, although various of nanostructured polyphosphates including porous microplates, hexagonal tablets, nanorods, etc. are achieved, the growth of polyphosphates directly on conductive material are seldom reported.19,21,23,26–29 One possible reason is that the polyphosphates are usually prepared at high temperature, which will lead to the shrink of the materials and induce the weak contact between polyphosphates and conductive substrates. Such an issue will detach polyphosphates from conductive substrate and therefore lead to poor stability in electrochemical reactions. Surface coating of active carbon on pseudocapacitive materials were widely applied as effective strategies to hold micro-structural stability.30–32 However, the carbon coatings usually need to be treated at high temperature (over 800 °C) to produce high conductivity, which may deteriorate the structure of active materials and conductive substrates.17,33 Surface coating of conductive polymers such as polypyrrole, polythiophene, and polyaniline on pseudocapacitive materials are also effective for improving conductivity.34,35 But the conducting polymers are not stable for practical application in electrochemical cells.8 With a two−dimensional graphite−like structure, carbon nitride (C3N4) has unique optical property, good thermal and chemical stability, inexpensive, ease of preparation, and environmentally benign. C3N4 has been widely applied as promising materials for photocatalysis and other related energy conversions.36–42 Subsequently, the combination of C3N4 with conductive substrate supported polyphosphates, both enhanced stability and favorable conductivity can be expected. In this work, uniform Ni2P2O7 nanoarrays composited with Ni foam substrate were achieved via facile hydrothermal growth and calcination conversions. Afterwards, C3N4 nanosheets can be directly decorated on the surface of Ni2P2O7 nanoarrays, with capability to prevent the Ni2P2O7 nanoarrays from fall off Ni foam during electrochemical reactions. The optimized C3N4/Ni2P2O7



composites on Ni foam delivered both high capacitance and enhanced long−term stability in three-electrode SCs. In addition, the fabricated C3N4/Ni2P2O7 nanoarrays also exhibited electrochemical performance as anode in asymmetric supercapacitor, which exhibit promising potential in energy storage devices. EXPERIMENTAL SECTION Materials synthesis The Ni foam supported NH4NiPO4·H2O nanorarrys were obtained through hydrothermal synthesis, which has been reported in our previous reports.35 For synthesis of Ni foam supported Ni2P2O7 arrays, Ni foam supported NH4NiPO4·H2O nanorarrys were calcined at 500 °C for 2 h in air. After cooling to room temperature, the products were used for characterizations directly. For preparation of C3N4 decorated Ni foam, urea (CH4N2O, 99 %, ACS reagent, Acros Organics) was dissolved into 10 ml deionized water. Then, Ni foam supported NH4NiPO4·H2O was immersed into the urea solution and maintained for about 0.5 h. The Ni foam supported NH4NiPO4·H2O nanorarrys was transferred into a crucible and calcined under air at 500 °C for 2 h with the heating rate was set as 1 °C min−1. After cooling down, nickel foam supported composites were ultrasonic cleaned in deionized water. Finally, the Ni foam supported materials were washed with ethanol and then put in drying oven at 60 °C for 12 h. Material characterizations, three−electrode electrochemical measurement, and fabrication of asymmetric supercapacitor cells are described in supporting information. RESULTS AND DISCUSSIONS The designed formation procedure for Ni2P2O7 arrays and C3N4 decorated Ni2P2O7 arrays are schematic given in Figure 1. Firstly the NH4NiPO4·H2O nanoarrays were synthesized and grown


Page 4 of 25

Page 5 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


on surface of Ni foam via a hydrothermal process. Then, the Ni foam supported Ni2P2O7 arrays can be readily obtained by calcinating the Ni foam supported NiNH4PO4·H2O precursor at 500 °C in air. For compositing C3N4 on Ni2P2O7 arrays, NiNH4PO4·H2O nanoarrays on Ni foam were immersed in fixed concentration of urea solutions. Afterwards, a similar calcination process was applied for preparing the final C3N4/Ni2P2O7 composites on Ni foam.22,43

Figure 1 Scheme of the synthetic process for Ni foam supported Ni2P2O7 arrays and C3N4 coated Ni foam supported Ni2P2O7 arrays.

X−ray diffraction (XRD) profiles for fabricated materials are presented (see Figure S1of supporting information). The diffraction peaks of NiNH4PO4·H2O and Ni are clearly observed for Ni foam supported NiNH4PO4·H2O nanoarrays (Figure S1a), which are consistent with our previous reports.35 After calcination at 500 °C, only diffraction peaks of Ni are observed as shown in Figure S1b, indicating that NiNH4PO4·H2O transformed into poorly crystallized Ni2P2O7.22 Figure S1c shows the XRD pattern of NiNH4PO4·H2O nanoarrays immersed in urea solution (3 mol L−1) and calcined at 500 °C. Similarly, the XRD pattern in Figure S1c also displays sharp Ni diffraction peaks, suggesting both Ni2P2O7 and C3N4 are of poor crystallinity in



such synthetic conditions. Further increasing the calcination temperature may gently improve the crystallinity of Ni2P2O7 and C3N4, but higher temperature contrarily destroyed the structure of Ni foam substrate. To study the morphology of Ni foam supported composites, scanning electronic microscopy (SEM) characterizations were performed. Figure 2a illustrates the SEM image for NiNH4PO4·H2O nanoarrays annealed at 500 °C (denoted as bare Ni2P2O7). In comparison with precursor of NiNH4PO4·H2O nanoarrays (Figure S2a−b, supporting information), the morphology of the materials can be perfectly maintained. The products of nanoplate arrays are vertically grown with size 5-10 µm. Figure 2b exhibits a magnified SEM image of some nanoplates, in which the smooth surface can clearly be observed with the thickness of ca. 100 nm. When Ni foam supported NiNH4PO4·H2O nanoarrays were soaked in 1 mol L−1 urea solution and calcined (denoted as C3N4−1/Ni2P2O7), the nanoplate arrays can be also maintained, but with some irregular particles produced on the surface of nanoplates as displayed from SEM image of Figure 2c. Further magnified SEM image shows the coarse surface of particles covered nanoplates (Figure 2d), which is different from bare Ni2P2O7. The thinckness of each nanoplate is approximate 120 nm. To confirm the elemental distribution, the energy dispersive spectrometer (EDS) mapping images are recorded The mapping images for N, P, O, Ni and C are displayed in Figure 2e. The plate array-like framework in each elemental image is similar and consistent with the morphology of SEM image, suggesting that the detected elements are distributed uniformly. By further increasing the urea concentration to 3 mol L−1 (denoted as C3N4−3/Ni2P2O7), the nanoarrays become blurry because the amount of C3N4 coating increased (Figure 2f). The enlarged SEM image in Figure 2g shows that the surface and space between each nanoplate are fully filled and the thickness of nanoplate is increased to 150 nm. When the


Page 6 of 25

Page 7 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


urea solution increased into 6 mol L−1 (marked as C3N4−6/Ni2P2O7), the nanoplate arrays can hardly be observed because the coating materials are too thick (Figure 2h). A typical Transmission electronic microscopy (TEM) image of C3N4−3/Ni2P2O7 in Figure 2i illustrates a nanoplate with the size of approximate 3 µm and surface covered with porous network. A higher magnified TEM image exhibits that the structure of C3N4−3/Ni2P2O7 consists of porous and thin nanosheets (Figure 2j). The clear boundary between thin sheet-like coating and microplate core can be observed. The selected area electron diffraction (SAED) pattern in Figure 2k do not show any diffraction spots or rings, indicating amorphous nature of the both core and shell. The possible existed bonds in our fabricated materials was characterized by Fourier transform infrared spectroscopy (FT−IR). The P2O7 group frequencies can be assigned to characteristic vibrations from PO3 group and P–O–P bridge. As Figure 2l displayed, absorption bands at 1086 and 583 cm−1 region are attributed to vibrations from PO3 species and weak band at round 947 cm−1 can be realized as models of P–O–P bridge.44 Absorption bands from 1371 to 1569 cm−1 are assigned to vibrations of aromatic C–N stretching, whereas the peak at 1637 cm−1 is ascribed to heterocycle C–N stretching vibrations.45 Broad peaks between 3500 and 3000 cm−1 are assigned to −OH vibrations from absorbed water molecules from enviroment.35 Based on the above analysis, amorphous C3N4 decorated NiP2O7 nanoarrays were formed in current synthetic process.



Figure 2 (a, b) SEM images of the bare Ni2P2O7; (c, d) SEM images and (e) EDS mapping images of the C3N4−1/Ni2P2O7; SEM images of (f, g) C3N4−3/Ni2P2O7 and (h) C3N4−6/Ni2P2O7; (i, j) TEM images, (k) SAED pattern, and (l) FT−IR of the C3N4−3/Ni2P2O7.

The states of elements in the prepared product are defined by X−ray photoelectron spectroscopy (XPS). Figure 3a shows the high−resolution spectrum of C 1s for C3N4−3/Ni2P2O7. The fitted peaks at binding energy of 284.8 eV is referred to C=C bonds in adventitious carbon. In addition there are fitted peaks at 285.7 and 288.7 eV, assigning to C−N bond and C=N bond in as fabricated C3N4, respectively.43 Figure 3b presents the N 1s spectrum. The peak at 398.9 eV is ascribed to sp2 N atoms from pyridine and a peak at 399.9 eV are caused by the bridging N


Page 8 of 25

Page 9 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


atoms from N−(C) or pyrrolic N-H donds.45 Figure 4c shows the P 2p peak centered at binding energy of 134.2 eV, indicating that +5 is the mainly state for P element.22 The Ni 2p spectrum presented in Figure 3c shows Ni 2p1/2 spectrum at binding energy of 874.4 eV and Ni 2p3/2 spectrum at binding energy of 856.7 eV. There are also two satellite peaks at binding energy of 879.8 and 861.7 eV, suggesting that the Ni is mainly in the state of 2+.46 Therefore, the analysis strongly suggests that the produced materials are C3N4 coated on Ni foam supported Ni2P2O7.

Figure 3 XPS spectra of possible existed elements in product of C3N4−3/Ni2P2O7: (a) N 2s, (b) C 1s, (c) Ni 2p, and (d) P 2p.

The electrochemical performance of these composites as electrode in three−electrode configuration was investigated. Figure 4a displays cyclic voltammetry (CV) curves for these products when scan rate is set as 5 mV s−1. All CV curves shows obvious redox behavior, suggesting quasi-reversible Faradaic reactions of charging and discharging are happened near the



electrolyte-electrode interfaces. In comparison with bare Ni2P2O7, broader anodic and cathodic redox peaks appears in C3N4 coated Ni2P2O7, which may be attributed to the psudocapacitive behavior of NiP2O7 (NiP2O7 + OH− ⇄ NiP2O7(OH) + e−).8,23,28,47 Galvanostatic charge−discharge (GCD) evaluations were set in potential window 0-0.55 V at current density of 2 mA cm−2. The shape of GCD curves are relatively symmetric as exhibited from Figure 4b, indicating that all products possessed favorable pseudocapacitive behavior. The specific capacitance is calculated as shown in Figure 4c, which are 3.2, 4.4, 2.7, and 0.6 F cm−2 for bare Ni2P2O7, C3N4−1/Ni2P2O7, C3N4−3/Ni2P2O7, and C3N4−6/Ni2P2O7, respectively. As shown in Table S1, as-fabricated composites deliver superior specific capacitance over most previous reports on transition-metal based compounds, for example, the Co3O4/CC (400 mF cm−2 at 4 mA cm−2),48 MnO@C/CC (720 mF/cm−2 at 4 mA/cm−2),48 Li2Co2 (MoO4)3 (1.03 F cm−2 at ~ 1 mA cm−2),49 NiCo2O4 nanoneedle arrays (1.44 F cm−2 at 2.78 mA cm−2),50 Co0.5Ni0.5DHs/NiCo2O4/CFP (~2.3 F cm−2 at 2 mAcm−2),51 Co3O4@MnO2 (0.56 F cm−2 at 11.25 mA cm−2).52 In electrochemical reactions over C3N4 coated Ni2P2O7, moderate C3N4 coating can form an effective interface between the Ni2P2O7 and C3N4, which may promote the diffusion of charge carrier OH- into the electrochemical active Ni2P2O7 and provide extra energy storage capability.39,53–55 However, too much C3N4 coating will decrease the contact area between electrolyte and Ni2P2O7, which hinder the OH- diffusion to surface of Ni2P2O7 and lead to the decrease of specific capacitance.53–55 For other possible influencing factors, the electrochemical impedance spectroscopy (EIS) (see Figure S3, supporting information) exhibits that both solution resistance (Rs) and charge–transfer resistance (Rct) for these product are quite closed, indicating the Rs and Rct have little effect to change the specific capacitance. To evaluate the stability, the charge and discharge cycles were run approximate 1,000 times with current density set at 2 mA


Page 10 of 25

Page 11 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


cm−2. As shown in Figure 4f, the capacitance of bare Ni2P2O7 and C3N4−1/Ni2P2O7 retains only 48% and 31% as their initial values. It is worth noting that the specific capacitance can retain 91% and 98% for bare C3N4−3/Ni2P2O7 and C3N4−6/Ni2P2O7 respectively, exhibiting much enhanced and favorable electrochemical stability.

Figure 4 (a) CV curves with scan rates set at 5 mVs−1, (b) GCD curves with current density set at 2 mA cm−2, (c) calculated specific capacitance under various current densities, and (d) longterm charging-discharging performance at 2 mA cm−2 for bare Ni2P2O7, C3N4−1/Ni2P2O7, C3N4−3/Ni2P2O7, and C3N4−6/Ni2P2O7.

The charge and discharge cycles indicates that loading a small amount of C3N4 in the composites did not improve the cycling stability. While loading moderate C3N4 coatings in C3N4−3/Ni2P2O7 and C3N4−6/Ni2P2O7 could effectively improve the electrochemical stability. As demonstrated by SEM and TEM analysis, small amount of C3N4 only decorated the surface of Ni2P2O7 and Ni foam in the form of particle-like thin layer; while the surface with enough C3N4 could generate networks covering both Ni2P2O7 and Ni foam substrate, which acted as stabilizer to prevent the Ni2P2O7 nanoarrays from peeling off as illustrated in scheme of Figure 5a. To confirm this point,



SEM images after charge and discharge for approximate 1,000 times were compared. For bare Ni2P2O7, most of nanoarrays fell off during the long time cycling (Figure 5b and Figure S4a in supporting information). A similar situation is observed when only small amount of C3N4 is loaded for C3N4−1/Ni2P2O7 (Figure 5c and Figure S4b in supporting information). When C3N4 coatings are increased (for the sample C3N4−3/Ni2P2O7), the morphology can be well maintained (Figure 5d-e and Figure S4c in supporting information). The similar protecting effect can be also seen for the sample of C3N4−6/Ni2P2O7 (Figure 5f and Figure S4d in supporting information), which shows that the morphology is perfectly kept after 1,000 cycles.

Figure 5 (a) The schematic structure of the C3N4−Ni2P2O7−Ni foam electrode; The SEM images of (b) Ni2P2O7, (c) C3N4−1/Ni2P2O7, (d) C3N4−3/Ni2P2O7, and (e) magnified area from the marked area of (d), and (f) C3N4−6/Ni2P2O7 after charge and discharge approximate 1,000 times at 2 mA cm−2.

Finally, a asymmetric supercapacitor (ASC) was assembled by using C3N4−3/Ni2P2O7 as positive electrode. The C3N4−3/Ni2P2O7 was selected because it showed high capacitance and favorable capacitance retention during charging-discharging cycles. The active carbon (AC) was


Page 12 of 25

Page 13 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


used as negative electrode, KOH solution was applied as electrolyte, and the positive and negative electrodes was separated by a diaphragm. Figure 6a shows the CV curves scanned under different voltages, exhibiting that a stable voltage window of 1.7 V can be reached. In the following measurements, the 1.6 V was used to give a more stable voltage window for the measurements of ASCs. The CV curves recorded at voltage windows of 0-1.6 V with scan rates set from 5 to 100 mV s−1 are displayed in Figure 6b, which exhibited a faradaic pseudocapacitive behavior and the shape maintained well. The GCD curves were measured at current densities from 2 to 30 mA cm−1 (Figure 6c). The shape of the GCD curves shows a little asymmetric, implying that there are irreversible reactions may happened during Faradic reactions. The value of specific capacitance was calculated, which are 862 mF cm−2 at 2 mA cm−2 and reduced to 339 mF g−1 at 30 mA cm−2 (Figure 6d). Such capacitance is superior than previous important works about Ni2P2O7 based ASCs, such as mesoporous Na−doped Ni2P2O7 // AC based ASC (32.6 mF cm−2 at 0.5 mAcm−2) mAcm−2)

23

21

and amorphous Ni2P2O7 powders // AC based ASC (30 mF cm−2 at 0.1

as shown in Table S1 of supporting information. The long-term charging and

discharging performance of ASC is evaluated under 2 mA cm−2 is displayed in Figure 6e. The electrochemical capacitance increases gradually at the beginning cycles, which is a result of the progressive activation process for electrode materials. After that, there is a slow decreases with capacitance loss is only 2.8 % as initial value after 2000 cycles, exhibiting that fabricated ASC have favorable cycling stability. The GCD curves between initial five cycles and last five cycles are compared (inset of Figure 6e). There are no obvious changes observed in GCD shape between initial five cycles and lasted five cycles, indicating high stability during the electrochemical reactions. In addition, in order to demonstrate a practical application, two ASCs were serried and charged to 3.0 V for lighting on a white light−emitting diode (LED, 2.0 V). As



Figure 6f demonstrated, the white LED can keep lighting (lasted approximate 14 minutes), indicating that the fabricated ACSs based on g−C3N4 modified Ni foam/Ni2P2O7 nanoarrays and AC have potential applications as power storage devices. The energy and power density are calculated on the basis of specific capacitance performance in Figure S5a of supporting information. The maximum energy density can reach 31 Wh Kg-1 and the maximum power density can reach 2.4 kW Kg-1 as displayed from Ragone plot (Figure S5b, supporting information).

Figure 6 (a) CV curves at 5 mV s−1 in different potentials, (b) CV curves at 5-100 mV s−1, (c) GCD at 2-30 mA cm−2, (d) specific capacitance at 2-30 mA cm−2, and (e) cycling ability of assembled ASC device (inset is the first and last five CD curves); (f) a demonstration of a lighted


Page 14 of 25

Page 15 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


LED by two serried ASCs.

CONCLUSION In conclusion, C3N4 thin nanosheets decorated Ni2P2O7 nanoarrays were fabricated via facile hydrothermal and calcination method. Optimized amount of C3N4 coatings could form nanosheet network covering on both Ni2P2O7 and Ni foam to protect the Ni2P2O7 nanoarrays during the charging and discharging reactions. The optimized composites deliver high pseudo−capacitance as 2.7 F cm−2 at 2 mA cm2 and enhanced cycling stability (retain 91% in 1,000 cycles) as SCs electrode in three−electrode system. When ASC was constructed by using AC as negative electrode and C3N4 decorated Ni2P2O7 nanoarrays as positive electrode, high pseudo−capacitance of 862 mF cm−2 at 2 mA cm−2 and favorable cycling stability can be achieved. The designed three layered structure of C3N4 / Ni2P2O7 nanoarray on Ni foam will provide a feasible and efficient strategy for constructing electrodes with high electrochemical performance, low cost, and natural abundance. ASSOCIATED CONTENT Supporting Information XRD patterns of the products, SEM image of the Ni foam supported precursor, EIS plots of the products, and a comparison with previously reported transition metal based materials. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding author



*E−mail: [email protected] (N. Zhang), [email protected] (X. Liu), ma. [email protected] (R. Ma) Funding This work is supported by National Natural Science Foundation of China (Grant No. 51402364), General Financial Grant from the China Postdoctoral Science Foundation (Grant No. 2016M592443), and Project of Innovation–Driven Planning in Central South University. Notes The authors declare no competing financial interest. REFERENCES (1)

Dunn, B.; Kamath, H.; Tarascon, J.-M. Electrical Energy Storage for the Grid: A Battery of Choices. Science. 2011, 334 (6058), 928–935.

(2)

Sheberla, D.; Bachman, J. C.; Elias, J. S.; Sun, C.-J.; Shao-Horn, Y.; Dincă, M. Conductive MOF Electrodes for Stable Supercapacitors with High Areal Capacitance. Nat. Mater. 2016, 16 (2), 220–224.

(3)

Simon, T.; Bouchonville, N.; Berr, M. J.; Vaneski, A.; Adrović, A.; Volbers, D.; Wyrwich, R.; Döblinger, M.; Susha, A. S.; Rogach, A. L.; Jäckel, F.; Stolarczyk, J. K.; Feldmann, J. Redox Shuttle Mechanism Enhances Photocatalytic H2 Generation on NiDecorated CdS Nanorods. Nat. Mater. 2014, 13 (11), 1013–1018.

(4)

Van der Ven, A.; Bhattacharya, J.; Belak, A. A. Understanding Li Diffusion in LiIntercalation Compounds. Acc. Chem. Res. 2013, 46 (5), 1216–1225.


Page 16 of 25

Page 17 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(5)

Chhowalla, M.; Shin, H. S.; Eda, G.; Li, L.-J.; Loh, K. P.; Zhang, H. The Chemistry of Two-Dimensional Layered Transition Metal Dichalcogenide Nanosheets. Nat. Chem. 2013, 5 (4), 263–275.

(6)

Wang, X.; Zhang, Y.; Zhi, C.; Wang, X.; Tang, D.; Xu, Y.; Weng, Q.; Jiang, X.; Mitome, M.; Golberg, D.; Bando, Y. Three-Dimensional Strutted Graphene Grown by SubstrateFree Sugar Blowing for High-Power-Density Supercapacitors. Nat. Commun. 2013, 4, 2905.

(7)

El-Kady, M. F.; Strong, V.; Dubin, S.; Kaner, R. B. Laser Scribing of High-Performance and Flexible Graphene-Based Electrochemical Capacitors. Science. 2012, 335 (6074), 1326–1330.

(8)

Lin, T.; Chen, I.-W.; Liu, F.; Yang, C.; Bi, H.; Xu, F.; Huang, F. Nitrogen-Doped Mesoporous Carbon of Extraordinary Capacitance for Electrochemical Energy Storage. Science. 2015, 350 (6267), 1508–1513.

(9)

Bonaccorso, F.; Colombo, L.; Yu, G.; Stoller, M.; Tozzini, V.; Ferrari, A. C.; Ruoff, R. S.; Pellegrini, V. Graphene, Related Two-Dimensional Crystals, and Hybrid Systems for Energy Conversion and Storage. Science. 2015, 347 (6217), 1246501–1246501.

(10)

Qu, L.; Zhao, Y.; Khan, A. M.; Han, C.; Hercule, K. M.; Yan, M.; Liu, X.; Chen, W.; Wang, D.; Cai, Z.; Xu, W.; Zhao, K.; Zheng, X.; Mai, L. Interwoven Three-Dimensional Architecture of Cobalt

Oxide Nanobrush-Graphene@NiXCo2X(OH)6X for High-

Performance Supercapacitors. Nano Lett. 2015, 15 (3), 2037–2044. (11)

Hu, H.; Guan, B. Y.; Lou, X. W. (David). Construction of Complex CoS Hollow Structures with Enhanced Electrochemical Properties for Hybrid Supercapacitors. Chem 2016, 1 (1), 102–113.



(12)

Wang, L.; Feng, X.; Ren, L.; Piao, Q.; Zhong, J.; Wang, Y.; Li, H.; Chen, Y.; Wang, B. Flexible Solid-State Supercapacitor Based on a Metal-Organic Framework Interwoven by Electrochemically-Deposited PANI. J. Am. Chem. Soc. 2015, 137 (15), 4920–4923.

(13)

Huang, Y.; Zhong, M.; Huang, Y.; Zhu, M.; Pei, Z.; Wang, Z.; Xue, Q.; Xie, X.; Zhi, C. A Self-Healable and Highly Stretchable Supercapacitor Based on a Dual Crosslinked Polyelectrolyte. Nat. Commun. 2015, 6, 10310.

(14)

Zhang, Y.-Z.; Cheng, T.; Wang, Y.; Lai, W.-Y.; Pang, H.; Huang, W. Flexible Supercapacitors: A Simple Approach to Boost Capacitance: Flexible Supercapacitors Based on Manganese Oxides@MOFs via Chemically Induced In Situ SelfTransformation. Adv. Mater. 2016, 28 (26), 5241–5241.

(15)

Wu, J. M.; Chang, W. E.; Chang, Y. T.; Chang, C. Piezo-Catalytic Effect on the Enhancement of the Ultra-High Degradation Activity in the Dark by Single- and FewLayers MoS2 Nanoflowers. Adv. Mater. 2016, 28 (19), 3718–3725.

(16)

Wang, J.; Zhang, X.; Wei, Q.; Lv, H.; Tian, Y.; Tong, Z.; Liu, X.; Hao, J.; Qu, H.; Zhao, J.; Li, Y.; Mai, L. 3D Self-Supported Nanopine Forest-like Co3O4@CoMoO4 Core–shell Architectures for High-Energy Solid State Supercapacitors. Nano Energy 2016, 19, 222– 233.

(17)

Salunkhe, R. R.; Tang, J.; Kamachi, Y.; Nakato, T.; Kim, J. H.; Yamauchi, Y. Asymmetric Supercapacitors Using 3D Nanoporous Carbon and Cobalt Oxide Electrodes Synthesized from a Single Metal–Organic Framework. ACS Nano 2015, 9 (6), 6288–6296.

(18)

Tang, J.; Salunkhe, R. R.; Liu, J.; Torad, N. L.; Imura, M.; Furukawa, S.; Yamauchi, Y. Thermal Conversion of Core-Shell Metal-Organic Frameworks: A New Method for


Page 18 of 25

Page 19 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Selectively Functionalized Nanoporous Hybrid Carbon. J. Am. Chem. Soc. 2015, 137 (4), 1572–1580. (19)

Li, B.; Gu, P.; Feng, Y.; Zhang, G.; Huang, K.; Xue, H.; Pang, H. Ultrathin Nickel-Cobalt Phosphate 2D Nanosheets for Electrochemical Energy Storage under Aqueous/Solid-State Electrolyte. Adv. Funct. Mater. 2017, 27 (12), 1605784.

(20)

Yuan, P.; Zhang, N.; Zhang, D.; Liu, T.; Chen, L.; Ma, R.; Qiu, G.; Liu, X. Controllable Synthesis of Layered Co–Ni Hydroxide Hierarchical Structures for High-Performance Hybrid Supercapacitors. J. Phys. Chem. Solids 2016, 88, 8–13.

(21)

Wei, C.; Cheng, C.; Wang, S.; Xu, Y.; Wang, J.; Pang, H. Sodium-Doped Mesoporous Ni2P2O7 Hexagonal Tablets for High-Performance Flexible All-Solid-State Hybrid Supercapacitors. Chem. - An Asian J. 2015, 10 (8), 1731–1737.

(22)

Chen, C.; Zhang, N.; He, Y.; Liang, B.; Ma, R.; Liu, X. Controllable Fabrication of Amorphous Co—Ni Pyrophosphates for Tuning Electrochemical Performance in Supercapacitors. ACS Appl. Mater. Interfaces 2016, 8 (35), 23114–23121.

(23)

Pang, H.; Zhang, Y.-Z.; Run, Z.; Lai, W.-Y.; Huang, W. Amorphous Nickel Pyrophosphate

Microstructures

for

High-Performance

Flexible

Solid-State

Electrochemical Energy Storage Devices. Nano Energy 2015, 17, 339–347. (24)

Yuan, P.; Zhang, N.; Zhang, D.; Liu, T.; Chen, L.; Liu, X.; Ma, R.; Qiu, G. Fabrication of Nickel-Foam-Supported

Layered

Zinc–cobalt

Hydroxide

Nanoflakes

for

High

Electrochemical Performance in Supercapacitors. Chem. Commun. 2014, 50 (76), 11188– 11190.



(25)

Page 20 of 25

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 (7), 934–942.

(26)

Hou, L.; Lian, L.; Li, D.; Lin, J.; Pan, G.; Zhang, L.; Zhang, X.; Zhang, Q.; Yuan, C. Facile Synthesis of Co2P2O7 Nanorods as a Promising Pseudocapacitive Material towards High-Performance Electrochemical Capacitors. RSC Adv. 2013, 3 (44), 21558.

(27)

Wang, S.; Jiang, X.; Du, G.; Guo, Z.; Jang, J.; Kim, S. J. Solvothermal Synthesis of Mn2P2O7 and Its Application in Lithium-Ion Battery. Mater. Lett. 2011, 65 (21–22), 3265–3268.

(28)

Senthilkumar, B.; Khan, Z.; Park, S.; Kim, K.; Ko, H.; Kim, Y. Highly Porous Graphitic Carbon and Ni2P2O7 for a High Performance Aqueous Hybrid Supercapacitor. J. Mater. Chem. A 2015, 3 (43), 21553–21561.

(29)

Wang, X.; Yan, Z.; Pang, H.; Wang, W.; Li, G.; Ma, Y.; Zhang, H.; Li, X.; Chen, J. NH4CoPO4·H2O

Microflowers

and

Porous

Co2P2O7

Microflowers:

Effective

Electrochemical Supercapacitor Behavior in Different Alkaline Electrolytes. Int. J. Electrochem. Sci. 2013, 8 (3), 3768–3785. (30)

Shi, C.; Zhao, Q.; Li, H.; Liao, Z. Low Cost and Fl Exible Mesh-Based Supercapacitors for Promising Large-Area Fl Exible / Wearable Energy Storage. Nano Energy 2014, 6, 82–91.

(31)

Wu, Z.-S.; Zhou, G.; Yin, L.-C.; Ren, W.; Li, F.; Cheng, H.-M. Graphene/metal Oxide Composite Electrode Materials for Energy Storage. Nano Energy 2012, 1 (1), 107–131.


Page 21 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(32)

Chen, G.; Zhou, M.; Catanach, J.; Liaw, T.; Fei, L.; Deng, S.; Luo, H. Solvothermal Route Based in Situ Carbonization to Fe3O4@C as Anode Material for Lithium Ion Battery. Nano Energy 2014, 8, 126–132.

(33)

Zhang, Y.; Foster, C. W.; Banks, C. E.; Shao, L.; Hou, H.; Zou, G.; Chen, J.; Huang, Z.; Ji, X. Graphene-Rich Wrapped Petal-Like Rutile TiO2 Tuned by Carbon Dots for HighPerformance Sodium Storage. Adv. Mater. 2016, 28 (42), 9391–9399.

(34)

Zhou, C.; Zhang, Y.; Li, Y.; Liu, J. Construction of High-Capacitance 3D CoO@Polypyrrole Nanowire Array Electrode for Aqueous Asymmetric Supercapacitor. Nano Lett. 2013, 13 (5), 2078–2085.

(35)

Chen, C.; Zhang, N.; Liu, X.; He, Y.; Wan, H.; Liang, B.; Ma, R.; Pan, A.; Roy, V. A. L. Polypyrrole-Modified NH4NiPO4·H2O Nanoplate Arrays on Ni Foam for Efficient Electrode in Electrochemical Capacitors. ACS Sustain. Chem. Eng. 2016, 4 (10), 5578– 5584.

(36)

Liu, J.; Liu, Y.; Liu, N.; Han, Y.; Zhang, X.; Huang, H.; Lifshitz, Y.; Lee, S.-T.; Zhong, J.; Kang, Z. Metal-Free Efficient Photocatalyst for Stable Visible Water Splitting via a Two-Electron Pathway. Science. 2015, 347 (6225), 970–974.

(37)

Zheng, Y.; Jiao, Y.; Chen, J.; Liu, J.; Liang, J.; Du, A.; Zhang, W.; Zhu, Z.; Smith, S. C.; Jaroniec, M.; Lu, G. Q. (Max); Qiao, S. Z. Nanoporous Graphitic-C3N4 @Carbon MetalFree Electrocatalysts for Highly Efficient Oxygen Reduction. J. Am. Chem. Soc. 2011, 133 (50), 20116–20119.

(38)

Zheng, Y.; Liu, J.; Liang, J.; Jaroniec, M.; Qiao, S. Z. Graphitic Carbon Nitride Materials: Controllable Synthesis and Applications in Fuel Cells and Photocatalysis. Energy Environ. Sci. 2012, 5 (5), 6717.



(39)

Page 22 of 25

Li, X.; Feng, Y.; Li, M.; Li, W.; Wei, H.; Song, D. Smart Hybrids of Zn2GeO4 Nanoparticles and Ultrathin G-C3N4 Layers: Synergistic Lithium Storage and Excellent Electrochemical Performance. Adv. Funct. Mater. 2015, 25 (44), 6858–6866.

(40)

Zhang, M.; Wang, X. Two Dimensional Conjugated Polymers with Enhanced Optical Absorption and Charge Separation for Photocatalytic Hydrogen Evolution. Energy Environ. Sci. 2014, 7 (6), 1902.

(41)

Chen, Q.; Zhao, Y.; Huang, X.; Chen, N.; Qu, L. Three-Dimensional Graphitic Carbon Nitride Functionalized Graphene-Based High-Performance Supercapacitors. J. Mater. Chem. A 2015, 3 (13), 6761–6766.

(42)

Wen, P.; Gong, P.; Sun, J.; Wang, J.; Yang, S. Design and Synthesis of Ni-MOF/CNT Composites and rGO/carbon Nitride Composites for an Asymmetric Supercapacitor with High Energy and Power Density. J. Mater. Chem. A 2015, 3 (26), 13874–13883.

(43)

Hou, Y.; Wen, Z.; Cui, S.; Guo, X.; Chen, J. Constructing 2D Porous Graphitic C3N4 Nanosheets/nitrogen-Doped

Graphene/layered

MoS2

Ternary

Nanojunction

with

Enhanced Photoelectrochemical Activity. Adv. Mater. 2013, 25 (43), 6291–6297. (44)

Kaoua, S.; Krimi, S.; Péchev, S.; Gravereau, P.; Chaminade, J. P.; Couzi, M.; El Jazouli, A. Synthesis, Crystal Structure, and Vibrational Spectroscopic and UV-Visible Studies of Cs2MnP2O7. J. Solid State Chem. 2013, 198 (3), 379–385.

(45)

Yang, S.; Gong, Y.; Zhang, J.; Zhan, L.; Ma, L.; Fang, Z.; Vajtai, R.; Wang, X.; Ajayan, P. M. Exfoliated Graphitic Carbon Nitride Nanosheets as Efficient Catalysts for Hydrogen Evolution under Visible Light. Adv. Mater. 2013, 25 (17), 2452–2456.


Page 23 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(46)

Salvatl, L.; Makovsky, L. E.; Stencel, J. M.; Brownls, F. R.; Hercules, D. M. Surface Spectroscopic Study of Tungsten-Alumina Catalysts Using X-Ray Photoelectron, Ion Scattering, and Raman Spectroscopies. J. Phys. Chem. 1981, 104 (1977), 3700–3707.

(47)

Pang, H.; Yan, Z.; Wang, W.; Chen, J.; Zhang, J.; Zheng, H. Facile Fabrication of NH4CoPO4·H2O

Nano/microstructures

and

Their

Primarily

Application

as

Electrochemical Supercapacitor. Nanoscale 2012, 4 (19), 5946–5953. (48)

Yu, N.; Guo, K.; Zhang, W.; Wang, X.; Zhu, M.-Q. Flexible High-Energy Asymmetric Supercapacitors Based on MnO@C Composite Nanosheet Electrodes. J. Mater. Chem. A 2017, 5 (2), 804–813.

(49)

Hercule, K. M.; Wei, Q.; Asare, O. K.; Qu, L.; Khan, A. M.; Yan, M.; Du, C.; Chen, W.; Mai, L. Interconnected Nanorods-Nanoflakes Li Co2(MoO4)3 Framework Structure with Enhanced Electrochemical Properties for Supercapacitors. Adv. Energy Mater. 2015, 5 (10), 1500060.

(50)

Zhang, G. Q.; Wu, H. Bin; Hoster, H. E.; Chan-Park, M. B.; Lou, X. W. (David). SingleCrystalline NiCo2O4 Nanoneedle Arrays Grown on Conductive Substrates as Binder-Free Electrodes for High-Performance Supercapacitors. Energy Environ. Sci. 2012, 5 (11), 9453.

(51)

Huang, L.; Chen, D.; Ding, Y.; Feng, S.; Wang, Z. L.; Liu, M. Nickel − Cobalt Hydroxide Nanosheets Coated on NiCo2O4 Nanowires Grown on Carbon Fiber Paper for HighPerformance Pseudocapacitors. ACS Appl. Mater. Interfaces 2013, 5, 11159–11162.

(52)

Liu, J.; Jiang, J.; Cheng, C.; Li, H.; Zhang, J.; Gong, H.; Fan, H. J. Co3O4 nanowire@MnO2 Ultrathin Nanosheet Core/shell Arrays: A New Class of HighPerformance Pseudocapacitive Materials. Adv. Mater. 2011, 23 (18), 2076–2081.



(53)

Zhang, L.; Ou, M.; Yao, H.; Li, Z.; Qu, D.; Liu, F.; Wang, J.; Wang, J.; Li, Z. Enhanced Supercapacitive Performance of Graphite-like C3N4 Assembled with NiAl-Layered Double Hydroxide. Electrochim. Acta 2015, 186, 292–301.

(54)

Xu, L.; Xia, J.; Xu, H.; Yin, S.; Wang, K.; Huang, L.; Wang, L.; Li, H. Reactable Ionic Liquid Assisted Solvothermal Synthesis of Graphite-like C3N4 Hybridized ??-Fe2O3 Hollow Microspheres with Enhanced Supercapacitive Performance. J. Power Sources 2014, 245, 866–874.

(55)

Chen, G.; Yan, L.; Luo, H.; Guo, S. Nanoscale Engineering of Heterostructured Anode Materials for Boosting Lithium-Ion Storage. Adv. Mater. 2016, 28 (35), 7580–7602.


Page 24 of 25

Page 25 of 25 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



Ni2P2O7 Nanoarrays with Decorated C3N4 Nanosheets as Efficient

Recommend Documents