Inverse spinel NiFeAlO4 as a highly active oxygen evolution electrocatalyst: promotion of activity by a redox-inert metal ion

Chen, Jamie Y. C.; Miller, Jeffrey T.; Gerken, James B.; Stahl, Shannon S.

doi:10.1039/c3ee43811b

Cited by 172 publications

(147 citation statements)

References 52 publications

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“…1), consistent with previous observations (7,11,12,20,21). The pure Ni material exhibits an isolated Ni 2+/3+ redox feature in the CV, with a midpoint potential of 0.53 V vs. NHE (normal hydrogen electrode), and a small redox feature (peak potential ∼0.76 V) at the foot of the large irreversible wave corresponding to the catalytic OER, which has an onset potential of ∼0.72 V. Introduction of iron into the oxide is known to increase the Ni 2+/3+ potential and decrease the onset potential for catalysis (7,11,12,20,21). With the 25% Fe-doped material, the two features are fully merged, and only a small shoulder is evident at the foot of the catalytic wave.…”

Section: Resultssupporting

confidence: 82%

Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

Goldsmith

Harshan

Gerken

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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204

161

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NiFe oxyhydroxide materials are highly active electrocatalysts for the oxygen evolution reaction (OER), an important process for carbon-neutral energy storage. Recent spectroscopic and computational studies increasingly support iron as the site of catalytic activity but differ with respect to the relevant iron redox state. A combination of hybrid periodic density functional theory calculations and spectroelectrochemical experiments elucidate the electronic structure and redox thermodynamics of Ni-only and mixed NiFe oxyhydroxide thin-film electrocatalysts. The UV/visible light absorbance of the Ni-only catalyst depends on the applied potential as metal ions in the film are oxidized before the onset of OER activity. In contrast, absorbance changes are negligible in a 25% Fe-doped catalyst up to the onset of OER activity. First-principles calculations of proton-coupled redox potentials and magnetizations reveal that the Ni-only system features oxidation of Ni 2+ to Ni 3+ , followed by oxidation to a mixed Ni 3+/4+ state at a potential coincident with the onset of OER activity. Calculations on the 25% Fedoped system show the catalyst is redox inert before the onset of catalysis, which coincides with the formation of Fe 4+ and mixed Ni oxidation states. The calculations indicate that introduction of Fe dopants changes the character of the conduction band minimum from Ni-oxide in the Ni-only to predominantly Fe-oxide in the NiFe electrocatalyst. These findings provide a unified experimental and theoretical description of the electrochemical and optical properties of Ni and NiFe oxyhydroxide electrocatalysts and serve as an important benchmark for computational characterization of mixedmetal oxidation states in heterogeneous catalysts.NiFe oxyhydroxide | oxygen evolution reaction | electrocatalysis | spectroelectrochemistry | density functional theory T he photoelectrochemical conversion of water into O 2 and H 2 is a major focus of energy storage and conversion efforts (1-4), with significant attention directed toward development of efficient catalysts for water oxidation and reduction. Such catalysts should operate at low overpotential, exhibit high selectivity, and be composed of earth-abundant materials. Commercial electrolyzers typically use transition-metal-oxide electrocatalysts for the oxygen evolution reaction (OER) (5, 6), and nickel, nickel-iron, and other mixed-metal oxides are especially effective under alkaline conditions (7,8). Despite the importance and potential future impact of these materials, many features of their catalytic mechanism are poorly understood.Nickel oxyhydroxide has long been associated with OER electrocatalysis (9, 10); however, much of the activity in this material has been shown to arise from the presence of Fe impurities (7, 11). This conclusion complements extensive independent studies demonstrating the effectiveness of NiFebased oxide and oxyhydroxide materials as OER electrocatalysts (12-14), including a survey of nearly 3,500 mixed-metal-oxide compositions, which drew attentio...

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Section: Resultssupporting

confidence: 82%

Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

Goldsmith

Harshan

Gerken

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

204

161

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“…Metal oxides consisting only of redox-inert metals generally exhibit poor OER characteristics because of the lack of redox centers; however, if redox-active transition metals are applied together, the redox-inert metals can facilitate the OER process by providing a redox metal with different electrondonating ability [137,[174][175][176] or stabilizing the structure of the catalysts. [27] In this respect, Zhang et al applied redox-inert Al to amorphous multimetal oxides.…”

Section: Other Amorphous Metal Oxidesmentioning

confidence: 99%

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

Kim

et al. 2018

Advanced Energy Materials

723

498

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fossil fuels are being widely researched for the development of a sustainable energy system. Among the various candidates for green energy resources, hydrogen energy has been at the center of attention. [1,2] Hydrogen is both inexhaustible and environmentally friendly, because it can be produced from earth-abundant reactants such as water and methane and because no CO 2 or other toxic products are emitted during its conversion into other energy form such as electricity, respectively. Moreover, hydrogen can exhibit significantly larger energy density compared with other energy sources such as gasoline and coal. The most widely used method of hydrogen production today is steam reforming because of its low cost in the process. [3] Nevertheless, the release of carbon monoxide or carbon dioxide as byproducts in the steam reforming process diminishes the environmental merits of hydrogen energy. Thus, as a possible cleaner alternative, an electrolysis method that involves producing hydrogen by electrochemically splitting water has been extensively investigated. Using one of the most abundant resources, water, the production of hydrogen from it yields only oxygen as a byproduct.In the water electrolysis, the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) occur simultaneously, as described by the following equationsIn order for the reaction to proceed, a voltage of 1.23 V is theoretically required between an anode and a cathode. However, an overpotential (represented by the symbol η) should be additionally applied to account for the potential loss resulting from kinetic limitations occurring during the electrochemical reaction. The use of electrocatalysts can lower the overpotential by kinetically facilitating the water-splitting reaction either in HER or OER. Due to the nature of four-electron involving OER, it is generally believed that the OER is much more sluggish than the HER; thus, the development of efficient OER Hydrogen is a promising alternative fuel for efficient energy production and storage, with water splitting considered one of the most clean, environmentally friendly, and sustainable approaches to generate hydrogen. However, to meet industrial demands with electrolysis-generated hydrogen, the development of a low-cost and efficient catalyst for the oxygen evolution reaction (OER) is critical, while conventional catalysts are mostly based on precious metals. Many studies have thus focused on exploring new efficient nonprecious-metal catalytic systems and improving the understandings on the OER mechanism, resulting in the design of catalysts with superior activity compared with that of conventional catalysts. In particular, the use of multimetal rather than single-metal catalysts is demonstrated to yield remarkable performance improvement, as the metal composition in these catalysts can be tailored to modify the intrinsic properties affecting the OER. Herein, recent progress and accomplishments of multimetal catalytic systems, including several important groups of catalysts: layered h...

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“…[ 232 ] After a detailed combinatorial survey of thousands of trimetallic oxides, Stahl et al have discovered that the inverse spinel NiFeAlO4 shows activity exceeding all other Ni/Fe mixed oxides. [ 233 ] NiCo2O4 improved its electrocatalytic behavior when prepared on a graphene-MnO2 3D framework. [234] Lithiated LixCoO2 spinels (x ≈ 0.5) have been proposed as bifunctional catalysts able to promote oxygen reduction and oxygen evolution reaction.…”

Section: Mixed Oxidesmentioning

confidence: 99%

Water Oxidation at Electrodes Modified with Earth‐Abundant Transition‐Metal Catalysts

2014

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Inverse spinel NiFeAlO4 as a highly active oxygen evolution electrocatalyst: promotion of activity by a redox-inert metal ion

Cited by 172 publications

References 52 publications

Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

Characterization of NiFe oxyhydroxide electrocatalysts by integrated electronic structure calculations and spectroelectrochemistry

Recent Progress on Multimetal Oxide Catalysts for the Oxygen Evolution Reaction

Water Oxidation at Electrodes Modified with Earth‐Abundant Transition‐Metal Catalysts

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