Scalable self-growth of Ni@NiO core-shell electrode with ultrahigh capacitance and super-long cyclic stability for supercapacitors

Yu, Minghao; Wang, Wang; Li, Cheng; Zhai, Teng; Lu, Xihong; Tong, Yexiang

doi:10.1038/am.2014.78

Cited by 299 publications

(171 citation statements)

References 39 publications

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“…The shoulder at 852.8 eV in Ni-NiO/N-rGO also indicates the presence of metallic Ni. [ 31 ] The full XPS spectra of Co-CoO/N-rGO and Ni-NiO/N-rGO are compared in Figure S3a The local environment of Co at CoO/N-rGO was very similar to that in CoO. [ 32 ] In good agreement with XPS analysis, the shoulder at 7712 eV in the spectrum of Co-CoO/N-rGO indicates the presence of metallic Co species.…”

Section: Resultssupporting

confidence: 58%

Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as Multifunctional Electrocatalysts

et al. 2015

Adv Funct Materials

521

253

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5799wileyonlinelibrary.com issues associated with energy security and environmental pollution. [1][2][3][4][5] Oxygen reduction reaction (ORR), oxygen evolution reaction (OER), and hydrogen evolution reaction (HER) are the most crucial electrochemical reactions to realize energy storage and conversion in these technologies. Although Pt-, Ir-, and Ru-based materials exhibit the highest activity for these electrochemical reactions, these precious-metal catalysts cannot be largely used for these clean energy because of their scarcity on earth and high cost. [ 6,7 ] Therefore, high-active, low-cost, and durable precious-metalfree catalysts from earth-abundant elements have been attracted considerable attention since last decade. [8][9][10][11] Among studied nonprecious metal catalysts, [ 12 ] nickel and cobalt are earth-abundant, low-cost, and environment-friendly materials that have widely been explored as electrocatalysts for the oxygen or hydrogen reactions in energy conversion and storage devices. [13][14][15] However, the pure cobalt and nickel oxides usually show insuffi cient electrical conductivity and low reactive surface areas, resulting in limited kinetics during these electrochemical reactions such as ORR, OER. [ 16 ] Oppositely, standalone metallic Ni or Co has good electrical conductivity, but is less active than Pt, because the formation energies of Ni-H or Co-H is lower than that of Pt-H for the HER. [ 17 ] Furthermore, combining graphene with metal or metal oxide is an effective way to improve catalytic activities due to the high surface area and excellent electrical conductivity of graphene, [18][19][20] thereby increasing number of active sites and promoting the charge transfer in electrodes. [21][22][23] For example, Co 3 O 4 /graphene, [ 24 ] Ni/graphene fi lm, [ 25 ] and NiO/rGO [ 26 ] composite catalysts have been explored showing enhanced catalytic activity, relative to single metals or metal oxides. Based on previous studies on the nickel or cobalt electrocatalysts, in this work, we synthesized a new family catalyst including Co-CoO/N-rGO and Ni-NiO/N-rGO via a pyrolysis of graphene oxide-supported cobalt and nickel salts, respectively. The possible synergetic effect among transition metals, metal oxides, and graphene was systematically studied, making them simultaneously highly active for the OER, ORR, or HER. Metal (Ni, Co)-Metal Oxides/Graphene Nanocomposites as Multifunctional ElectrocatalystsXien Liu , Wen Liu , Minseong Ko , Minjoon Park , Min Gyu Kim , Pilgun Oh , Sujong Chae , Suhyeon Park , Anix Casimir , Gang Wu , * and

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Section: Resultssupporting

confidence: 58%

Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as Multifunctional Electrocatalysts

et al. 2015

Adv Funct Materials

521

253

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“…30,[45][46][47] The continuous increase in capacitance in the rst 40 000 cycles is contradictory to the fact that b-Ni(OOH) has poorer electrochemical activity than g-Ni(OOH). 30 We ascribe the increased capacitance to the gradual transition of the Ni core of the dendrites into b-Ni(OOH) during the cycling process, 48,49 resulting in exceptionally superior cycle life and good capacitance as compared with other recent reports. 17,[50][51][52] This gradual transition of Ni into b-Ni(OOH) during cycling does not affect the coulombic efficiency or the rate capability too much (Fig.…”

Section: Resultsmentioning

confidence: 79%

Ni@NiO core/shell dendrites for ultra-long cycle life electrochemical energy storage

Liu

Zhang

et al. 2016

J. Mater. Chem. A

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A dendritic Ni@NiO core/shell electrode (DNE) is successfully fabricated by electrodeposition in a Ni-free electrolyte, with a Ni anode providing Ni ions through dissolution and diffusion. The unique structure is ideal for electrochemical energy storage since the dendrites provide a large surface area for easy electrolyte infiltration; the metal core improves the electrode conductivity with a shortened ion diffusion path, and the metal oxide shell is active for faradaic charge storage. As a result, the synthesized DNE demonstrates a high specific capacitance of 1930 F g À1 and a high areal capacitance of 1.35 F cm À2 , with super-long cycle stability. The gravimetric capacitance of the DNE hardly shows any decay after 70 000 cycles at a scan rate of 100 mV s À1 . It was also demonstrated that our electrodeposition method in a source-free electrolyte is universal to deposit dendritic Ni-compounds on many other types of substrates, versatile for different applications.

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“…3,4 In this context, various nanosize electrode materials with greatly improved electrochemical performance have been synthesized. [5][6][7][8][9] Thereupon a fundamental question arises: do smaller electrode materials exhibit better electrochemical performance?…”

Section: Introductionmentioning

confidence: 99%

Ultra-small, size-controlled Ni(OH)2 nanoparticles: elucidating the relationship between particle size and electrochemical performance for advanced energy storage devices

et al. 2015

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Nanosizing is the fashionable method to obtain a desirable electrode material for energy storage applications, and thus, a question arises: do smaller electrode materials exhibit better electrochemical performance? In this context, theoretical analyses on the particle size, band gap and conductivity of nano-electrode materials were performed; it was determined that a critical size exist between particle size and electrochemical performance. To verify this determination, for the first time, a scalable formation and disassociation of nickel-citrate complex approach was performed to synthesize ultra-small Ni(OH) 2 nanoparticles with different average sizes (3.3, 3.7, 4.4, 6.0, 6.3, 7.9, 9.4, 10.0 and 12.2 nm). The best electrochemical performance was observed with a specific capacity of 406 C g − 1 , an excellent rate capability was achieved at a critical size of 7.9 nm and a rapid decrease in the specific capacity was observed when the particle size was o7.9 nm. This result is because of the quantum confinement effect, which decreased the electrical conductivity and the sluggish charge and proton transfer. The results presented here provide a new insight into the nanosize effect on the electrochemical performance to help design advanced energy storage devices. INTRODUCTIONRecently, electrochemical energy storage devices, such as batteries and supercapacitors, have attracted great attention because of their many advantages compared with other power-source technologies. However, these devices could realize further gains in energy and power densities if the electrochemical performance of electrode materials is largely improved. 1,2 Reducing the dimensions of electrode materials down to the nanoscale level is an effective strategy to promote their electrochemical performance, which primarily benefits from the nanosize effect, that is, achieving a higher surface area and a shorter ion diffusion length. 3,4 In this context, various nanosize electrode materials with greatly improved electrochemical performance have been synthesized. 5-9 Thereupon a fundamental question arises: do smaller electrode materials exhibit better electrochemical performance?According to the relationship between the band gap (E g ) and the size (a) of a nanoparticle (for semiconductor) defined by [Equation (1)] 10-12

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Scalable self-growth of Ni@NiO core-shell electrode with ultrahigh capacitance and super-long cyclic stability for supercapacitors

Cited by 299 publications

References 39 publications

Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as Multifunctional Electrocatalysts

Metal (Ni, Co)‐Metal Oxides/Graphene Nanocomposites as Multifunctional Electrocatalysts

Ni@NiO core/shell dendrites for ultra-long cycle life electrochemical energy storage

Ultra-small, size-controlled Ni(OH)2 nanoparticles: elucidating the relationship between particle size and electrochemical performance for advanced energy storage devices

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