Spin state engineered ZnxCo3−xO4 as an efficient oxygen evolution electrocatalyst

Ramsundar, Rani M.; Pillai, Vijayamohanan K.; Joy, P.A.

doi:10.1039/c8cp06641h

Cited by 31 publications

(25 citation statements)

References 55 publications

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“…Spinel Co 3 O 4 is one of the most-studied OER electrocatalysts because of its high activity and relative earth-abundance of Co. − Extensive efforts have been made to improve its OER activity by fabricating nanostructures to increase the surface area, , morphology control to expose more active crystal facets, , and doping to modulate its electronic structure. − In the spinel structure of Co 3 O 4 , the tetrahedral ( T d ) sites are occupied by Co 2+ with e 4 t 2 3 electron configuration, whereas the octahedral ( O h ) sites are Co 3+ with t 2g 6 e g 0 electron configuration (see Figure a) . Because T d coordinated Co 2+ and O h coordinated Co 3+ exhibit different electronic properties, which site is the active site in the OER is an open question.…”

Section: Introductionmentioning

confidence: 99%

Ni³⁺-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of Ni_xCo_3–xO₄ Electrocatalysts

et al. 2019

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This work reports a systematical study on the relationship of electronic structure to oxygen evolution reaction (OER) activity of Ni x Co3–x O4 (x = 0–1) mixed oxides. The specific OER activity is substantially increased by 16 times from 0.02 mA cm–2 BET for pure Co3O4 to 0.32 mA cm–2 BET for x = 1 at an overpotential of 0.4 V and exhibits a strong correlation with the amount of Ni ions in the +3 oxidation state. X-ray spectroscopic study reveals that inclusion of Ni3+ ions upshifts the occupied valence band maximum (VBM) by 0.27 eV toward the Fermi level (E F), and creates a new hole (unoccupied) state located ∼1 eV above the E F. Such electronic features favor the adsorption of OH surface intermediates on Ni x Co3–x O4, resulting in enhanced OER. Furthermore, the emerging hole state effectively reduces the energy barrier for electron transfer from 1.19 to 0.39 eV, and thereby improves the kinetics for OER. The electronic structure features that lead to a higher OER in Ni x Co3–x O4 can be extended to other transition metal oxides for rational design of highly active catalysts.

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Section: Introductionmentioning

confidence: 99%

Ni³⁺-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of Ni_xCo_3–xO₄ Electrocatalysts

et al. 2019

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“…As a result, the mass density of (100)‐oriented LaCoO 3 (87% IS) is 2.9 and 6.7 times higher than those of (110) and (111)‐oriented LaCoO 3 (31% IS and 48% IS). Currently, research efforts on spin states of catalysts are mainly based on the regulation of lattice planes, [ 139 ] heteroatom doping, [ 140–142 ] and material dimensions. [ 143–145 ] However, design and production of these catalysts are technically complicated.…”

Section: Magnetic Field‐assisted Electrocatalytic Her/oermentioning

confidence: 99%

Promoting Electrocatalytic Hydrogen Evolution Reaction and Oxygen Evolution Reaction by Fields: Effects of Electric Field, Magnetic Field, Strain, and Light

et al. 2020

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promising alternative to fossil fuels. Water electrolysis by renewable resourcederived electricity represents a facile and green route to produce H 2. [1-13] Generally, the key to implement high-performance water splitting is to develop economically viable, efficient, and robust electrocatalysts to lower the activation potential barriers. Thus far, researchers have devoted extensive enthusiasm to the investigation of electrocatalysts. Currently, most efforts have been taken on the search for new materials, [14-16] regulation of morphology, [17] crystallinity, [18] facet, [19] component, [20-24] defect, [25,26] matter phase, [27,28] or the compositing of various materials with synergy. [29-36] However, the performances of emerging nonnoble electrocatalysts still lag behind those of noble ones. To address this issue, researchers have turned their attention beyond the electrocatalysts themselves. Field-assisted electrocatalysis is the electrocatalytic reaction proceeded in the presence of a field. It represents a promising methodology since it exerts an additional degree of freedom to engineer an electrochemical process. Inspiringly, indisputable improvements in electrocatalytic hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) have been implemented with the assist of various fields, including electric field, magnetic field, strain, and light. For example, the electrocatalytic HER of a MoS 2 nanosheet is markedly boosted by simply exploiting a back gate voltage of 5 V. [37] Its overpotential at −100 mA cm −2 is decreased from 240 to 38 mV. In addition, enhancement of alkaline water electrolysis is achieved by applying a moderate magnetic field (≤450 mT) to an electrocatalytic anode consists of highly magnetic electrocatalysts. [38] Its current density increments are beyond 100%. Furthermore, the HER activity of β-PdH x increases monotonically as the applied strain increases from 0% to 4.5%. [39] Lastly, an approximately threefold increase in current density of Au-MoS 2 for electrocatalytic HER is realized upon the illumination of IR light. [40] These results undoubtedly elucidate that applying a field during electrocataly sis opens up great opportunities toward further improving electrocatalytic activity. Moreover, this approach provides merits of facile, dynamical, continuous, reversible, and universal control. Despite fascinating achievements, these investigations are relatively scattered. The underneath mechanisms and principles Hydrogen fuel is considered as one of the most clean renewable resources, warranting it a primary alternative to fossil fuels for future energy supplies. Electrocatalytic water splitting is an eco-friendly technique for high-purity hydrogen production. However, the sluggish dynamics of its two halfreactions, hydrogen evolution reaction (HER) and oxygen evolution reaction (OER), are tough challenges impeding the practical application of this technology. In these years, external field-assisted HER and OER have attracted extensive research interests. Herein, the effects o...

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“…12,13 Recent findings have revealed that, in spinel Co 3 O 4 , Co 3+ in the octahedral sites is active for the OER, 14,15 which has encouraged attempts to prepare Co 3 O 4based catalysts with Co 2+ replaced by other transition metal ions in which only Co 3+ is involved in the OER. 16,17 On the contrary, some reports have shown that Co 2+ in tetrahedral sites is active and can be easily oxidized to form CoOOH, while Co 3+ is rather inactive and may be blocked by OH groups. 18 These ongoing debates on the OER activity, particularly involving ZnCo 2 O 4 material, have yet to be resolved.…”

Section: ■ Introductionmentioning

confidence: 99%

Nanostructuring Matters: Stabilization of Electrocatalytic Oxygen Evolution Reaction Activity of ZnCo₂O₄ by Zinc Leaching

Naveen

Bui

Lee

et al. 2022

ACS Appl. Mater. Interfaces

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Despite the enormous attention paid to cobalt oxide materials as efficient water splitting electrocatalysts, a deep understanding of their activity discrepancy is still elusive. In this work, we showed that stabilization of the internally generated oxygen evolution reaction (OER) active phase (oxyhydroxide) is crucial for ZnCo 2 O 4 electrocatalysts. A systematic evaluation of the bulk and nanostructured ZnCo 2 O 4 system concomitant with nanostructured Co 3 O 4 showed that leaching of Zn is the driving force behind the near-surface transformation to the oxyhydroxide phase. The relative contribution to this near-surface reconstruction was found to be surface-sensitive. The electrochemical observations combined with Raman and impedance spectroscopy revealed that the good catalytic activity could be attributed to the formation of the cobalt oxyhydroxide phase, which was created by the dissolution of Zn from the nanostructured surface. Moreover, this study sheds light on previous contradicting postulates regarding the discrepancy of the OER activity of ZnCo 2 O 4 . Our finding regarding the formation of the OER active phase in spinel Zn−Co oxide will motivate researchers to focus more on the near-surface reconstruction behavior of cobalt-based oxide electrocatalysts in the future.

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Spin state engineered Zn_xCo_3−xO₄ as an efficient oxygen evolution electrocatalyst

Abstract: The electrocatalytic activity of ZnxCo3−xO4 for the oxygen evolution reaction is correlated with the population of high-spin Co3+ and the Co3+/Co2+ ratio.

Cited by 31 publications

References 55 publications

Ni³⁺-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of Ni_xCo_3–xO₄ Electrocatalysts

Ni³⁺-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of Ni_xCo_3–xO₄ Electrocatalysts

Promoting Electrocatalytic Hydrogen Evolution Reaction and Oxygen Evolution Reaction by Fields: Effects of Electric Field, Magnetic Field, Strain, and Light

Nanostructuring Matters: Stabilization of Electrocatalytic Oxygen Evolution Reaction Activity of ZnCo₂O₄ by Zinc Leaching

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Spin state engineered ZnxCo3−xO4 as an efficient oxygen evolution electrocatalyst

Abstract: The electrocatalytic activity of ZnxCo3−xO4 for the oxygen evolution reaction is correlated with the population of high-spin Co3+ and the Co3+/Co2+ ratio.

Cited by 31 publications

References 55 publications

Ni3+-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of NixCo3–xO4 Electrocatalysts

Ni3+-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of NixCo3–xO4 Electrocatalysts

Promoting Electrocatalytic Hydrogen Evolution Reaction and Oxygen Evolution Reaction by Fields: Effects of Electric Field, Magnetic Field, Strain, and Light

Nanostructuring Matters: Stabilization of Electrocatalytic Oxygen Evolution Reaction Activity of ZnCo2O4 by Zinc Leaching

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Spin state engineered Zn_xCo_3−xO₄ as an efficient oxygen evolution electrocatalyst

Ni³⁺-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of Ni_xCo_3–xO₄ Electrocatalysts

Ni³⁺-Induced Hole States Enhance the Oxygen Evolution Reaction Activity of Ni_xCo_3–xO₄ Electrocatalysts

Nanostructuring Matters: Stabilization of Electrocatalytic Oxygen Evolution Reaction Activity of ZnCo₂O₄ by Zinc Leaching