Fabrication of hierarchical flower-like super-structures consisting of porous NiCo2O4 nanosheets and their electrochemical and magnetic properties

Liu, Zhao‐Qing; Xiao, Kang; Xu, Qizhi; Li, Nan; Su, Yu‐Zhi; Wang, Hongjuan; Chen, Shuang

doi:10.1039/c3ra23084h

Cited by 160 publications

(93 citation statements)

References 40 publications

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“…[ 52 ] The X-ray diffraction data (XRD) of the solution-grown nanorods (Figure 2 b, top trace) are in good agreement with literature values for a NiCo 2 O 4 spinel structure. [ 48,51,53 ] For the catalyst electrode (bottom trace), the data are dominated by the (002) and (100) refl ections from the N-CNTs (marked by * and #, respectively), although the (311) and (400) NiCo 2 O 4 refl ections are also distinguishable. [ 54,55 ] The conclusion is thus that the nanorods exist in a polycrystalline spinel NiCo 2 O 4 structure, and that they are well-dispersed and well-anchored onto the N-CNTs.…”

Section: The Electrocatalyst Electrodementioning

confidence: 99%

“…We assign this spectral change to the observed direct interactions between the NiCo 2 O 4 nanorods and the N-CNTs in the catalyst electrode (see Figure 1 ). [48][49][50][51] The presence of N-CNTs in the catalyst electrode is manifested in the characteristic D-band and G-band at 1390 cm −1 and 1650 cm −1 , respectively. [ 52 ] The X-ray diffraction data (XRD) of the solution-grown nanorods (Figure 2 b, top trace) are in good agreement with literature values for a NiCo 2 O 4 spinel structure.…”

Section: The Electrocatalyst Electrodementioning

confidence: 99%

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Toward a Low‐Cost Artificial Leaf: Driving Carbon‐Based and Bifunctional Catalyst Electrodes with Solution‐Processed Perovskite Photovoltaics

Sharifi

Larsen

Wang

et al. 2016

Advanced Energy Materials

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countries, where many users still are not connected to the electric grid, it is clear that alternative energy technologies are needed that can contribute with renewable fuels in signifi cant amounts. In this challenging context, researchers have found inspiration in the process of natural photosynthesis when they attempt to convert the plentiful, but intermittent, solar irradiation incident on the Earth's surface into a storable fuel, using a range of methods commonly coined as artifi cial photosynthesis. [1][2][3][4][5][6][7][8][9] One emerging technology to achieve such solar-to-fuel conversion is the "artifi cial-leaf device", which essentially comprises an assembly of photovoltaics (PVs) that drives two electrocatalyst electrodes immersed in water. [10][11][12] This device produces molecular hydrogen and oxygen using only sunlight and water as the input, and during the past few years its performance has improved drastically, with the current record for the solar-to-hydrogen (STH) conversion efficiency being above 10%. [13][14][15][16] It is, however, clear that in order to become truly sustainable and useful, the artifi cial-leaf device should comprise solely, or predominantly, earth-abundant materials and be produced with scalable and low-cost methods. Moreover, from a processing and transport point of view, it is preferable if it can be lightweight and fl exible.Perovskite materials [ 14,[17][18][19][20][21] have recently emerged as an interesting option to incumbent silicon [ 15,20 ] and copperindium-gallium-selenide [ 16,20 ] for the active material in PVs, due to a high and quickly improving solar-to-electric (STE) conversion effi ciency and an opportunity for cost-effi cient, solutionbased fabrication. [ 17,18,21,23 ] The electrocatalyst electrode comprises a catalytically active material deposited on the surface of a current collector. Commonly employed materials for the current collector are bulk or porous metals, [ 15 ] whereas a popular choice for the catalyst is various types of metal-oxides. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] From a system-cost and practicality perspective, it is desirable to develop a functional lightweight and low-cost current collector and to identify a catalyst that is bifunctional in that it can drive the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) in the same water solution. [ 14,[39][40][41][42][43][44] Here, we present an artifi cial-leaf device that delivers an STH effi ciency of 6.2% and a Faradaic H 2 evolution effi ciency of 100%. We mention that our device is not fully integrated at this stage, Molecular hydrogen can be generated renewably by water splitting with an "artifi cial-leaf device", which essentially comprises two electrocatalyst electrodes immersed in water and powered by photovoltaics. Ideally, this device should operate effi ciently and be fabricated with cost-effi cient means using earth-abundant materials. Here, a lightweight electrocatalyst electrode, comprising large surface-area NiCo 2 O 4 nano...

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Section: The Electrocatalyst Electrodementioning

confidence: 99%

Section: The Electrocatalyst Electrodementioning

confidence: 99%

Toward a Low‐Cost Artificial Leaf: Driving Carbon‐Based and Bifunctional Catalyst Electrodes with Solution‐Processed Perovskite Photovoltaics

Sharifi

Larsen

Wang

et al. 2016

Advanced Energy Materials

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“…[9][10] Recently nickel cobaltite with the spinel structure has been extensively investigated because of its ferromagnetic and electrocatalytic properties. [11][12] Moreover, this low cost ternary metal oxide has been studied as an emerging material for supercapacitors, [13][14][15] expected to fulfil the requirements for the ever-increasing demand for energy storage due to their high specific power, fast charge-discharge and long cycle life.…”

Section: Introductionmentioning

confidence: 99%

Cation distribution and vacancies in nickel cobaltite

Loche

Marras

Carta

et al. 2017

Phys. Chem. Chem. Phys.

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Samples of nickel cobaltite, a mixed oxide occurring in the spinel structure which is currently extensively investigated because of its prospective application as ferromagnetic, electrocatalytic, and cost-effective energy storage material were prepared in the form of nanocrystals stabilized in a highly porous silica aerogel and as unsupported nanoparticles.Nickel cobaltite nanocrystals with average size 4 nm are successfully grown for the first time into the silica aerogel provided that a controlled oxidation of the metal precursor phases is carried out, consisting in a reduction under H2 flow followed by mild oxidation in air. The investigation of the average oxidation state of the cations and of their distribution between the sites within the spinel structure, which is commonly described assuming the Ni cations are 2 only located in the octahedral sites, has been carried out by X-ray Absorption Spectroscopy providing evidence for the first time that the unsupported nickel cobaltite sample has a Ni:Co molar ratio higher than the nominal ratio of 1:2 and a larger than expected average overall oxidation state of the cobalt and nickel cations. This is achieved retaining the spinel structure, which accommodates vacancies to counterbalance the variation in oxidation state.3

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“…In addition, a band close at 185 cm -1 was observed in spectra for the nickel cobalt-containing mass oxide. The bands 185, 465, 551 and 655 cm -1 are related to the vibrational modes F 2g , E g , F 2g and A 1g , respectively [46][47][48] . Independent of the solution used, the deposited coatings present bands in the region between 465 and 655 cm -1 , which are also present in the bulk mixed oxide sample.…”

Section: Microstructural Characterization Of the Coatingsmentioning

confidence: 99%

The Effect of Electrolyte pH on the Ni-Co Mixed Oxides Coatings Produced from Citrate Baths

et al. 2018

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In this work, Ni-Co oxides coatings were produced using electrochemical techniques (chronopotentiometry and/or linear voltammetry) and solutions containing Ni 2+ and Co 2+ ions in the molar ratio 1: 2, sodium citrate as the ligand, and different pH values (7.5 and 10.5). Energy dispersive spectrometry (EDS), scanning electron microscopy (SEM), Raman spectroscopy (LRS) and electrochemical impedance spectroscopy (EIS) were used to characterize these coatings. The results showed that both pH values favored the production of Ni-Co oxide phases, independent of the electrochemical technique used. The EDS analysis indicated that it was possible to produce of oxides coating presenting different Ni:Co ratios using electrodeposition process. However, the morphology, the microstructure and the electrocatalytic ability of the coatings depended on both the pH and on the electrochemical technique used to produce them. The coatings produced using pH 10.5 were suitable to be used as electrocatalysts for the oxygen evolution reaction (OER).

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Fabrication of hierarchical flower-like super-structures consisting of porous NiCo2O4 nanosheets and their electrochemical and magnetic properties

Cited by 160 publications

References 40 publications

Toward a Low‐Cost Artificial Leaf: Driving Carbon‐Based and Bifunctional Catalyst Electrodes with Solution‐Processed Perovskite Photovoltaics

Toward a Low‐Cost Artificial Leaf: Driving Carbon‐Based and Bifunctional Catalyst Electrodes with Solution‐Processed Perovskite Photovoltaics

Cation distribution and vacancies in nickel cobaltite

The Effect of Electrolyte pH on the Ni-Co Mixed Oxides Coatings Produced from Citrate Baths

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