Nickel/Iron Oxide Nanocrystals with a Nonequilibrium Phase: Controlling Size, Shape, and Composition

Bau, Jeremy A.; Li, Peng; Marenco, Armando J.; Trudel, Simon; Olsen, Brian C.; Luber, Erik J.; Buriak, Jillian M.

doi:10.1021/cm501881a

Cited by 38 publications

(33 citation statements)

References 78 publications

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“…[29] The lattice spacing observed in [Ni,Fe]O indicates the likely lattice expansion. [30] Direct band gaps of~4.5 eV estimated from the electronic absorption spectra ( Figure S4) of both the films are similar to the values reported for NiO. [31] This, together with the elemental composition, XPS and HRTEM data discussed above, as well as the redox characterization discussed later, confirm the formation of NiO and [Ni,Fe]O in the thin film.…”

Section: Communicationssupporting

confidence: 82%

Insulating Polymer‐Hydrogel Nanocomposite Thin Film ‐ Based Catalytic Electrode for Efficient Oxygen Evolution Reaction

Madhuri

Radhakrishnan

2019

ChemElectroChem

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The counter-intuitive choice of an insulating polymer for embedding electrocatalysts is shown to facilitate a simple and general strategy to fabricate catalytic electrodes for efficient oxygen evolution reaction (OER) during water splitting. The hydrogel characteristics and appreciable swelling of the polymer in aqueous medium are the key enabling factors; electrolyte absorbed in the polymer matrix is likely to be involved in the electrocatalytic process. Nanocomposite thin films of chitosan spin-cast on common conducting substrates, with an optimal content of NiO and [Ni,Fe]O nanoplates generated through a facile and simple in situ protocol, are shown to effect OER with excellent overpotentials (down to 240 mV at 10 mA/ cm 2 ), low Tafel slope, high Faradaic efficiency, appreciable turnover frequency, and extended stability with high current density. Preliminary investigations with a range of catalystpolymer combinations illustrate the general applicability of the approach.The generation of ever more efficient electrocatalysts for the fundamentally important oxygen and hydrogen evolution reactions (OER and HER) has been the prime focus in the water splitting and related energy research front. Equally important and challenging, but relatively less focused on, is the development of simple and general protocols for the fabrication of robust electrodes bearing the catalyst. Methods like electrodeposition are commonly used to fabricate catalytic electrodes, but their temporal stability under electrolysis and gas-forming conditions can be limited; prominent issues include catalyst dissolution requiring compensation by feeding the relevant ions in the electrolyte, [1] and adverse composition changes of mixed metal oxide catalysts over extended electrolytic runs. [2] The critical problem of fixing powder catalysts has been highlighted in recent studies. Mills and coworkers have discussed the relevance of 'powder-to-electrode' fabrication, in particular the utility of a mechanical, solvent-free approach. [3][4][5] The problem has also been addressed by replacing common binders like Nafion having relatively low electrical conductivity, by carbon material generated from polymer precursors; [6] the latter step requires calcination at 450°C. Enhancement of electrode surface wettability using electrochemically inert but super-hydrophilic carbon nitride that enables also wider exposure of the catalyst sites, is another interesting approach, [7] but again involves high temperature (550°C) calcination and multiple fabrication steps. New strategies to fabricate stable catalyst electrodes, avoiding multiple steps and lengthy processing are desirable. We envisioned that hydrogel polymers, even if electrically insulating, would be widely adaptable and versatile matrices for embedding electrocatalysts that carry out efficient water splitting. Swelling of the polymer in aqueous medium makes this unlikely choice of material highly relevant, and an optimal polymer-catalyst combination can ensure a robust and efficient electrode system; ...

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Section: Communicationssupporting

confidence: 82%

Insulating Polymer‐Hydrogel Nanocomposite Thin Film ‐ Based Catalytic Electrode for Efficient Oxygen Evolution Reaction

Madhuri

Radhakrishnan

2019

ChemElectroChem

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“…This was exploited in the templating of silica with ionic liquids which provided materials with excellent pore volumes and surface areas [100][101][102][103][104], in the large-scale synthesis of monodispersed bridged polysilsesquioxane nanoparticles [105], or when reacting metal precursors bearing bulky organic groups [106]; (iii) Carboxylates bind strongly to the metals and therefore could work as surfactants hindering further growth of particles. Monodispersed metal oxide nanoparticles have been prepared in this way [107][108][109].…”

Section: Carboxylic Acids In Nhsgmentioning

confidence: 99%

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

et al. 2017

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This review is devoted to non-hydrolytic sol-gel chemistry. During the last 25 years, non-hydrolytic sol-gel (NHSG) techniques were found to be attractive and versatile methods for the preparation of oxide materials. Compared to conventional hydrolytic approaches, the NHSG route allows reaction control at the atomic scale resulting in homogeneous and well defined products. Due to these features and the ability to design specific materials, the products of NHSG reactions have been used in many fields of application. The aim of this review is to present an overview of NHSG research in recent years with an emphasis on the syntheses of mixed oxides, silicates and phosphates. The first part of the review highlights well known condensation reactions with some deeper insights into their mechanism and also presents novel condensation reactions established in NHSG chemistry in recent years. In the second section we discuss porosity control and novel compositions of selected materials. In the last part, the applications of NHSG derived materials as heterogeneous catalysts and supports, luminescent materials and electrode materials in Li-ion batteries are described.

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“…71 The similar OER performance (overpotential and Tafel slope) of these rocksalt phase nanoparticles to other Ni-Fe oxide catalysts can be better understood by analysis of the surface structure of these nanoparticles. Specifically, in our previous work, 62 irradiation. The UV irradiation deposited on electrode surfaces led to films that adhered to the ITO surface, and could be electrochemically cycled, and maintained at 10 mA/cm 2 for two hours.…”

Section: Electrochemistry All Electrochemistry Was Performed Using Amentioning

confidence: 99%

Oxygen Evolution Catalyzed by Nickel–Iron Oxide Nanocrystals with a Nonequilibrium Phase

Bau

Luber

Buriak

2015

ACS Appl. Mater. Interfaces

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Mixed nickel-iron oxides are of great interest as electrocatalysts for the oxygen evolution reaction (OER), the kinetically challenging half-reaction required for the generation of hydrogen gas from water via electrolysis. Previously, we had reported the synthesis of single crystal, soluble nickel-iron oxide nanoparticles over a wide range of nickel:iron compositions, with a metastable cubic rock salt phase ([Ni,Fe]O) that can be isolated despite the low solubility of iron in cubic nickel oxide at ambient temperatures. Here, activity for OER was examined, catalyzed by these [Ni,Fe]O nanoparticles integrated with indium tin oxide (ITO) electrodes. Because the as-prepared [Ni,Fe]O nanoparticles are oleate-capped, the surface ligands needed to be removed to induce adherence to the ITO substrate, and to enable charge transfer and contact with water to enable OER catalysis. Two different approaches were taken to reduce or eliminate the coverage of oleate ligands in these films: UV irradiation (254 nm) and air plasma. UV irradiation proved to lead to better results in terms of stable and OER-active films at pH 13. Kinetic analysis revealed that the Tafel slopes of these nanoparticle [Ni,Fe]O OER electrodes were limited by the electrochemical surface area and were found to be within the range of 30 to 50 mV/decade. Across the four compositions of Ni:Fe studied, from 24:76 to 88:12, the observed overpotential at 10 mA/cm2 for the OER in basic conditions decreased from 0.47 to 0.30 V as the proportion of nickel increased from 24% to 88%.

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Nickel/Iron Oxide Nanocrystals with a Nonequilibrium Phase: Controlling Size, Shape, and Composition

Cited by 38 publications

References 78 publications

Insulating Polymer‐Hydrogel Nanocomposite Thin Film ‐ Based Catalytic Electrode for Efficient Oxygen Evolution Reaction

Insulating Polymer‐Hydrogel Nanocomposite Thin Film ‐ Based Catalytic Electrode for Efficient Oxygen Evolution Reaction

The Power of Non-Hydrolytic Sol-Gel Chemistry: A Review

Oxygen Evolution Catalyzed by Nickel–Iron Oxide Nanocrystals with a Nonequilibrium Phase

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